Wildlife information at the click of a mouse--
Content Updated: 29th May 2014
Q: What is Mange?
A: There are several different types of mange, but the most common found in foxes is sarcoptic mange. Sarcoptic mange is a skin disease caused by a small (2 to 4 mm or less than one-quarter inch) parasitic mite (Sarcoptes scabiei var. vulpes), several thousand of which may burrow into a single square-centimetre (about one-sixth of a square inch) of skin. In humans, S. scabiei causes the condition commonly referred to as "scabies" and foxes have been known to infect the occasional human. Female mites burrow into the skin where they may live for as long as two months. Excretions from the mite harden to from a crust on the skin, leading to lacerations, hair loss and possible secondary bacterial infections. Conjunctivitis and changes in behaviour (the infected fox becomes less and less active) are also common. So intense is the irritation caused by this mite, that foxes are reputed to have gnawn off appendages! Weight loss and organ damage are sometimes evident and, if left untreated, death follows in four to six months. Indeed, the impact of mange on fox populations may be dramatic; the outbreak in 1994 succeeded in wiping out 95% of Bristol's fox population in only two years.
Foxes undergoing their summer moult are sometimes mistaken for those suffering from mange, because the infection starts from the hind quarters and spreads forward; infected foxes often have very bedraggled looking hips and tails. The Sarcoptes scabiei parasite (above, right) is conventionally treated with Ivermectin, although sulphur with arsenicum is a common homeopathic alternative. According to an article in the BBC Wildlife Magazine during July 2001, severely infected foxes may be taken into captivity for treatment, although it seems that they may return to find their territory has been taken over by another fox within a few days. For more detailed coverage, please see the main Sarcoptic Mange article. (Back to Menu)
Q: It’s all very well for you to sit at your computer and tell people that foxes only kill pets to feed themselves and don’t kill for sport. What do you know about the grief associated with losing a pet to a fox?
A: Until a few years ago, nothing! As I sit and write this, my mind drifts back to the events of Thursday 6th November 2003 and the surprise that I recall feeling upon getting up to investigate the quacking of our two pet "Call" ducks. For those of you who are familiar with the 9 standardized and half-dozen or more non-standardized types of Call duck listed by the British Wildfowl Association in 1999, one was a "Grey" or "Mallard" and the other was a "Bibbed" duck.
Anyhow, looking out of my dining room window, I saw the Bibbed duck (named Flick - the brown duck in the photo on the left) lying almost motionless on the netting of our fishpond, pinned down by an adolescent fox. Shouting “Oh no you don’t!” or some such -- admittedly slightly more explicit -- harangue, I shot through the kitchen and flew out of the back door shouting at the top of my lungs. I had hoped that shouting at the fox would cause it to drop the duck and flee – I was wrong; it did indeed flee, although much to my increasing despair took its quarry with it. We have a fence and gazebo-type structure separating our garden roughly in half – “A ha” thought I as I chased the fox up the garden, “It’ll have to drop the duck to get under the fence”. Wrong again! The fox slipped under the fence -- a gap of only some 12.5 cm (5 in) -- with the duck still clasped firmly in its jaws. It then went around our shed and over the back garden wall, with me in hot pursuit, screaming for all I was worth!
Where I used to live, the back gardens of each row of houses back on to each other, with a narrow gap of about 60 cm (about 2ft) separating the two opposing gardens. This area was overgrown, with brambles, discarded glass, bricks, paving slabs and the odd tree interspersed for good measure. It was along this rugged ‘alleyway’ that the fox took our duck. I screeched like an opera singer with an appendage caught in a car door, and the fox dropped the duck into a small crevice under some steel pipes. Looking desperately, I spotted Flick floundering in this pit and chirping in a quiet and rhythmic manner (signifying stress). Now, had I been thinking clearly I would’ve gone back into the house, got the telescopic loppers and hacked my way through the undergrowth something akin to the great Scottish Missionary Dr David Livingstone. However, I was concerned that the fox may return in my absence, and I was damned if I was going to just leave Flick there to die from his injuries.
Ergo, I clambered -- rather ungracefully it has to be said -- on to the wall and down into the undergrowth. I clambered across broken bricks and paving slabs, being reasonably careful to avoid the glass. Squeezing through the bifurcated trunk of a smallish tree, I found myself entangled in branches and bramble. All this time I was talking at Flick to try and reassure him. I finally fought my way through the brambles, and was just able to lift the steel pipes off him. Picking him up, and holding him close to my chest I began my travels back to the familiarity of my garden, talking to him all the way. We made it back, and in the light of day I could see that he was bleeding quite badly. I tore a handkerchief from the washing line as I scurried past and used it to cover his head, to reduce stress (thanks for that tip, Animal Hospital!). I put him in his hutch and raced in doors to phone the vet and get him an appointment.
At the vet's he was examined, and we found a large cut about 3cm (about 1.5 in) long and about 2cm (1 in) deep. The fox’s teeth had cut clean through his skin and into his breast muscle. Fortunately, it had not punctured his air sac (lungs) or he would’ve died almost immediately. We left him at the vet, returning a couple of hours later to pick up our newly sewn-up duck. Upon collecting him we were told that, during the surgery ,they had found not one, but four punctures, all of about the same size and depth – one from each of the fox's canines. We put him in his hutch, and he was confined for about a week. The first night was tense and it was with serious trepidation that we looked in the hutch the following morning – to our relief we found Flick still in the land of the living. It was quite likely that the trauma of the situation could have killed him that night. We hoped that, over the next fortnight, he would make a satisfactory recovery and we did everything within our power to aid and expedite the situation. Sadly, upon our return to the vet a week later, Flick had to be put-to-sleep – he hadn’t eaten anything over that week and was shaking and chattering quietly. The vet considered that he might have received brain damage during the incident.
In the long run, I suppose it would’ve been sensible to let the fox take Flick. However, at the time I was not thinking clearly and acted on impulse. Immediately after we lost Flick, his brother (Flash) seemed distressed at the loss of his sibling and became aggressive. Since Flick’s departure, we have got Flash a playmate (called Storm) and the two follow each other around like they’re chained together! Although Flash is still aggressive towards my Mum (and it seems, women in general), he has improved and seems a much happier duck. We have also made some alterations to our garden now and have more control over where the ducks are allowed to wander – we have not seen sight or sound of the fox since, despite hearing that a family down our street lost a rabbit recently.
So, has this changed my perception of foxes? Do I have a compelling urge to don a red coat and join the group affectionately referred to by The Guardian as the “Tally-Ho Brigade”? No, not at all. As a rational person, I see that the fox was only doing what it has evolved to do: feed itself and its family. However painful the situation was for Flick and our family (both emotionally and physically – I have the scars and rashes on my hands, arms, shoulders and face to prove I’ve ‘been there, done that’!), I don’t blame the fox one bit. I will concede that I was gob-smacked that this attack happened at 1.30pm in the afternoon -- the irony of it being lunchtime is not completely lost on me -- during broad daylight, when I had hitherto considered foxes nocturnal or crepuscular (i.e. dawn and dusk) predators. However, you learn something new everyday.
Intriguingly, none of my family blames the fox either, and I find this almost as refreshing as those people who suffer terrible mutilation at the jaws of a shark and then campaign for the protection of these magnificent fish. Getting scratched and stung whilst attempting to rescue a small duck from the dinner table of a fox is one thing, but being hauled from the water by a lifeguard and waking up in the hospital missing an appendage must be harrowing. Moreover, for these people to maintain the opinion that ‘well, the shark was just doing what it supposed to be doing and our two worlds just, kinda collided!’ is a type of clarity and fortitude that I could only hope to possess. (Back to Menu)
Q: Why shouldn’t I feed foxes (and dogs in general) chocolate?
A: I was an avid watcher of the BBC’s Animal Hospital program, and almost every week the vets would see a dog that had developed a sweet-tooth and helped itself to its owner’s secret stash of chocolate. The problem that dogs have with chocolate is, however, a serious one, and revolves around how they digest a specific ingredient: theobromine. Theobromine is part of a family of chemicals called methylxanthines (nitrogenous organic molecules), related to caffeine. Milk chocolate contains anywhere up to five grams (the average is about 2 g) per kilogram of theobromine, while dark chocolate can have twice as much. Humans take, on average, between four and six hours to metabolise (break down) theobromine; dogs take about 20 hours to do the same. According to the American Society for the Prevention of Cruelty to Animals, theobromine is toxic to dogs at 150 to 200 mg per kilogram body weight (the average lethal dose being about 300 mg per kg), although it varies with breed and individual and problems have been noticed at levels as low as 20 mg per kg. It is generally the case that a dog would have a stomach ache after eating about 240 grams of dark chocolate (about half a 'gift' box), although this may not prove toxic.
In dogs, methylxanthines are absorbed by the intestines after which they are carried -- via the hepatic portal vein -- to the liver. Some of the methylxanthines are successfully excreted by the liver, but many make it into the inferior vena cava (the vessel that takes the blood into the right-hand side of the heart) where it travels through the pulmonary (lung) circulation and into the main circulatory system. The situation is compounded by the fact that some of the methylxanthine by-products excreted by the liver into the bile ducts can be converted back into methylxanthines and reabsorbed by the small intestine. Ultimately, this means that dogs cannot effectively breakdown and excrete theobromine.
Theobromine causes excitation of the central nervous system, while also stimulating the heart and increasing blood pressure. Signs of theobromine poisoning in animals usually include excitement (i.e. nervousness and trembling), vomiting and/or diarrhoea, excessive thirst, muscle spasms and possibly seizures. Coma and death (resulting from alteration of normal heart rhythm) are rare but possible outcomes. According to vet Janet Crosby, if caught in time, theobromine poisoning can be treated with IV fluids, emetics (vomit-inducers), activated charcoal, anti-seizure medications and cardiac medications. It is worth remembering that it is not only dogs that are susceptible to chocolate poisoning, most animals are – cats, rats and mice are all well documented to suffer as a result of eating chocolate. Indeed, cats are more sensitive to theobromine than dogs (i.e. the average toxic dose for a cat is about 100 mg per kg less than for a dog) but, perhaps fortunately for them, cats have a genetic mutation in one of their taste buds which means they apparently cannot taste sweet flavours and are therefore less attracted to chocolate. (Back to Menu)
Q: Why does my dog seem to have a penchant for rolling in fox’s dung?
A: This -- sometimes infuriating -- behaviour probably stems back to your pet pooch’s wild ancestors: wolves. To illustrate this, let’s say a wolf leaves the pack and ventures off on its own to forage or explore a territory. On its wander, it comes across a novel smell (let’s say the fox excrement that all dog owners dread!). The best way to share this 'interesting' smell with the other members of its pack (without the aid of a poop-scoop bag) is to roll in the substance from which the smell is emanating. In this instance, the dog rolls in the fox scat, ensuring that it covers the sides of the face. When it returns to its pack, the other wolves greet it by sniffing noses and will readily detect this novel scent. Some canine behaviourists consider that a domestic dog rolling in dung may be a ‘hangover’ from their ancestors. However, it is noteworthy (I shy away from the word “interesting” in this instance!) that my dog only seems prone to rolling in fox faeces – apparently opting to ignore the scat of other creatures (i.e. cows, deer and other domestic dogs), although she is apparently rather unique in this respect. To my mind, larger canids might be more interested in other predator odours than the odours of prey - after all, foxes represent a competitor if you're a wolf.
Another theory is that by rubbing themselves in the scent of some other creature, they can mask their own scent and thus are less likely to be detected by a potential prey item, should they venture downwind of it. This makes sense; deer likely run when they catch the scent of a wolf, but probably ignore foxes unless there are calves/fawns around. At any rate, the jury is still out as to the precise reason for this particular behaviour, and the motive is probably associated with the specific odiferous substance and the relish with which the dog ‘applies’ it. (Back to Menu)
Q: On the BBC's Hunting TalkingPoint site, one participant said: "The fox is not 'our [Britain's] natural wildlife', it was introduced from France for the sport of the Normans and to help keep down the rabbits they had previously introduced here (another non-native species) and which had got out of control". Is this true?
A: Conventionally, species “native” to a given country are regarded as those that have arrived since the last ice age, without human assistance. Such species are also often referred to as being indigenous. The last ice age to grip Britain ended some 15,000 years ago, and pre-glacial Britain had both rabbits and foxes. As with many apparently off-the-cuff proclamations about foxes, the one given on the TalkingPoint site has elements of truth buried in an otherwise rather inaccurate statement.
The first archaeological evidence for the Red fox (Vulpes vulpes) in Britain comes from the Wolstonian Glacial sediments in Warwickshire (a county in the midlands, just south-east of Birmingham). The Wolstonian Glaciation started about 330,000 years ago and ended some 135,000 years before the present day (BP). The same sediments also contain the first evidence for the Eurasian badger (Meles meles) in Britain. During the Wolstonian, the landscape was probably mainly grasses and sedges with some dispersed woodland (this type of environment is called a “steppe”, by ecologists).
Following the retreat of ice from the last ice age (the oddly-named “Late Glacial”) some 15,000 years ago, many of the larger mammal species began to re-appear or extend their range northwards. Among these mammals were the wolf (Canis lupis), Brown bear (Ursus arctos), Reindeer (Rangifer tarandus) and contrary to popular misconception, the Woolly mammoth (Mammuthus primigenius). It was originally believed that the mammoth didn’t return to Britain after the maximum of (height of) the last glaciation. However, the remains of four specimens (one adult and three juveniles) found in a kettle-hole (a pit full of sticky grey, sandy clay) in Shropshire have been radiocarbon-dated to 12,800 BP.
According to Derek Yalden’s fascinating book, The History of British Mammals, post-glacial remains of the Red fox have been found at several sites around Britain and suggest that this species re-appeared naturally around 10,000 years ago, as the ice of the Devensian Glaciation (70,000 to 10,000 BP) retreated. Perhaps the best examples of post-glacial fox remains in the UK are at Gough’s Cave in Somerset, where Red fox remains have been found together with the remains of the Arctic fox (Vulpes lagopus). Indeed, even if one were to approach the question from a purely literary perspective, foxes are mentioned in the Catholic texts of Bede and Alucin, both of which pre-date the arrival of the Normans. I’m told that the Alucin actually admonished boys for spending their time digging foxes out of holes, rather than praying!
The question of whether rabbits (Oryctolagus cuniculus) are indigenous to Britain is somewhat more complicated. Rabbit remains have been found dating back to the warm climate of the Cromerian Interglacial (750,000 to 350,000 BP). However, it seems that rabbits didn’t make their own way back to Britain after the cessation of the last ice age. Rather, it seems that rabbits may have been introduced by Roman settlers. In 2005 archaeologists excavating a Roman settlement at Lynford in Norfolk found the remains of a 2,000 year old rabbit dinner, which may represent the earliest evidence of rabbits in post-glacial Britain. Prior to this it had been considered that rabbits were re-introduced to Britain by the Normans during the 12th Century (probably to provide food and fur). Invariably, Norman settlers did bring their own rabbits, but it doesn't look like they were the first! The precise date and source of the Norman introductions remain unclear, although the earliest definite mention of a rabbit warren is apparently from the Isles of Scilly in 1176. Although rabbits originate from the western Mediterranean, the Norman Kingdom in Sicily may have provided a likely contact with -- as well as source of -- rabbits for Britain. Thus, although rabbits are well known from pre-glacial Britain, they failed to reappear until the Normans brought them over some 900 years ago – this means that they cannot be considered truly indigenous to Britain.
Although the Red fox is a native species to Britain, this is not to say that the idea of foxes being introduced “from France for the sport of the Normans” is unfounded. Indeed, there is considerable evidence to support the introduction of foxes from outside the UK when fox populations declined. In his 1987 book, Running with the Fox, Prof. David Macdonald of Oxford University notes:
“Where numbers ran short [caused by hunting and a mange epidemic] foxes were bought and released (such ‘bagged’ foxes sold for 10 shillings [50p] at the Leadenhall Market [in London] in 1845) and included a brisk trade in imports from the Continent.”
In conclusion, we can say that foxes are part of Britain’s native fauna, although rabbits are not. The Normans introduced rabbits to Britain and ‘re-stocked’ foxes when their numbers declined dramatically during the mid-to-late 1800s. (Back to Menu)
Q: Foxes are well known to kill more than they can eat at the time. This behaviour often leads to foxes being branded “malicious” or “evil”, and merely the word “fox” is enough to bring out negative emotions in many livestock owners. Why do foxes kill to excess when such activity seems to represent a waste of energy and resources for a wild animal?
A: The observation that foxes can do tremendous damage to domestic livestock is one of the pivotal arguments for the continuation of hunting by the pro-hunting lobby. Unfortunately, there is no denying that foxes do kill livestock and sometimes do so to what appears to the casual human observer as “excess”. The counter-argument to “well foxes kill all the chickens in the coop but only take a couple” is normally something along the lines of “that’s because the fox was disturbed during the caching process. If you’d have slept through the ordeal, you would have come out to find your coup devoid of most of the hens”. Unfortunately, there are no studies to support or refute this idea. The basis for this argument is that foxes can only carry a single bird at any one time (making the process of caching slow) and the livestock owner usually comes to investigate the disturbance before the fox has had time to remove and store more than one or two birds. Unfortunately, this is not necessarily accurate – there are many examples where foxes have killed two or three ducks, decapitating the birds, and have left the carcasses otherwise untouched. It is instances such as these that have perpetuated the belief that “foxes kill for sport”, or that they kill because they “enjoy” killing. Indeed, while following a fox hunting debate on an Internet discussion list recently, I read a post by a gentleman who considered that foxes only attacked our pets because they’re too small to attack us! (Photo: Very young foxes are well known to cache food, suggestions some genetic predisposition to do so.)
First let us deal with the idea that foxes get some pleasure out of killing, or kill for sport. For a predator, killing is a pivotal part of their existence; it's not an exercise-based leisure activity. Quite simply, to the exclusion of scavenging (which is highly unpredictable), if they don't kill something else they starve to death. At the same time, it seems reasonable to assume that an animal wouldn't perform a particular action (especially one as dangerous as chasing, capturing and killing another animal) if it disliked doing so. Consequently, in order to ensure that an action so crucial to their survival continues, predators have probably evolved to gain some enjoyment from hunting. Think about reproduction - in order to ensure they're passed to successive generation, our genes programme us to be rewarded (with the 'hormone of love', oxytocin) for having sex. If sex wasn't fun, nobody would engage in it and the species would die out (test tubes and geneticists notwithstanding!).
So, do foxes enjoy killing? Yes, they probably do - they have evolved to kill to feed themselves and their families and a conscience or dislike of doing so would hamper their surival. However, does enjoying the hunt make them "wicked"? Quite simply, no. So far as anyone has been able to tell, predators are indifferent, even apathetic, to the lives or “feelings” of their prey, in the same way that their prey is indifferent to the lives and feelings of their predators! Predators just do what they do. The adjectives “malicious” and “evil” are often used when referring to the predatory behaviour of foxes (and indeed many predators). I think that Aidan Martin sums up this debate quite nicely on his ReefQuest site. Aidan writes:
“Sharks lack a moral code, which is a necessary prerequisite for choosing to behave in a manner that could be called ‘evil’. Sharks simply do what they do without ill will or premeditation and thus cannot be labelled ‘malicious’.”
Although the above statement refers to sharks, it does well for foxes (or any other predator). In fact, the only animal to which it does not apply is a human! Humans have a moral code -- that is, a set of often-complex statements of right and wrong -- and, under most circumstances, an ethical code - predators do not. With this in mind, it seems rather unhelpful to judge predators by our own cultural values.
The act of hunting can generally be broken down into a series of discrete events: Searching; Detection; Approach; Stalking; Chasing; Capture; and Kill. I use the term “generally” because any given hunt may not involve all of these, and the sequence of events referred to as “hunting” varies greatly depending on the circumstances. Indeed, according to Hans Kruuk, Professor of Zoology at Aberdeen University, hunting depends on both prey and environment, coupled with the predator’s own motivation and hunger. If prey is easily available (i.e. none of the risks associated with the chase and capture are present), then a predator doesn’t need to be hungry to readily take the quarry. This scenario -- where a predator kills without the motivation of hunger, or kills more than is necessary to sate its hunger -- is referred to as Surplus Killing.
Surplus killing is not a feature unique to foxes; wolves, leopards, caracals, coyotes, hyenas, bears, shrews, mink, polecats and weasels are among some of the many species known to surplus kill. Indeed, even animals in our homes are guilty of this; domestic cats are a prime example. One summer, several years back, while clearing some overgrown vegetation at the back of the garden, I made the discovery of what can only be described as a ‘bird larder’. In the back corner of my neighbour’s garden was a cluster of four or five dead birds. Now, while I cannot say for certain that my cats were to blame (there were many cats in the neighbourhood), we had received several dead birds on our patio earlier in the summer. To my mind, this larder was a result of surplus killing by a local cat (communal hoarding is known, but is rare in mammals) – more birds were killed than were needed to satisfy hunger and the surfeit were stored away in a secluded, over-grown corner for later use.
Many hypotheses have been proposed to explain the occurrence of surplus killing and they can generally be divided into two schools of thought: exploitation of a bounty; pathological killing through hyper-stimulation. The first school consider that surplus killing arises as a result of a predator stumbling across a bountiful food source, which -- because wild animals can never be sure where the next meal is coming from -- they exploit it to its full potential.
The second school believe that surplus killing is a form of so-called “pathological killing”. In other words, predators do not know how to react when prey fail to run away – a situation that is not “normal” in nature, so the predator has not evolved to deal with it. In a fascinating 1972 review of surplus killing in carnivores, Hans Kruuk set out the idea of pathological killing. Kruuk proposed that this ‘killing orgy’ may result from a predator’s killing mechanism being continually sparked off by the stimulus of one prey animal after another to catch – in effect, the predator’s instinct to kill prey is being over-stimulated. Under most circumstances, prey animals in the vicinity of a victim have fled by the time the kill has been made; thus, there are no more prey to chase. With all this in mind, surplus killing events do seem to have one common feature: there is a lack of defence by the prey. The prey may be in an enclosure, they may have lost their anti-predator mechanisms through domestication, or they may be restricted by adverse weather conditions (e.g. storms, moonless nights, snow etc.). In his book Hunter and Hunted, Kruuk suggests that, because hunger only motivates a predator in the early stages of a hunt sequence, even a sated predator will continue to take prey if the necessity for search, stalk, chase etc. have been removed (although a sated predator will not search for more food). Moreover, Kruuk notes that predators have no specific inhibition (with the exception, perhaps, of fatigue) to stop killing if prey is in abundance. (Photo: A haphazardly cached rabbit)
The effects of surplus killing events on prey populations are largely unknown, although instances of surplus killing are rare, suggesting that prey populations probably have sufficient time for recovery. Indeed, I’m aware of only a handful of instances where surplus killing has driven a prey population close to extirpation. In one of these cases, during the late 1960s, Red fox numbers had to be artificially-controlled to prevent the complete removal of a colony of Black-headed gulls (Larus ridibundus - left), which were being killed at a rate of some 200 birds per night, in northern Scotland. This particular example occurred during a spate of very dark and stormy nights, during which researchers found that they could walk up and pick the birds off their nests; the birds wouldn’t fly up and made little or no attempt to prevent being held by the biologists. Under normal weather conditions, the birds would take to the air as soon as an observer approached too close and would certainly protest to being picked up.
The act of killing more than you can eat at any given time appears to represent a significant waste, both in terms of the food resource and the predator's energy budget. According to my dictionary, the verb “waste” suggests, “to use, consume or expend [a resource] thoughtlessly, carelessly, or to no avail” or that a resource is “produced in excess of what is required”. Waste can, however, also mean, “fail to take advantage of” a resource or situation. Immediately we are struck by the idea that, just as a predator may be considered to have ‘wasted’ a resource by killing more than it requires to sate its hunger, the animal could similarly be considered to have ‘wasted’ the opportunity to obtain more food when the situation arose by not killing to surfeit! I consider this to be something akin to going to the supermarket and buying your weekly shopping. You pick up a joint of meat and put it in the trolley, despite the fact that you’re probably not planning to consume that meat for a few days -- perhaps Sunday lunch -- and, for that matter, you’re probably not even hungry while traipsing up and down the aisles. You’ll probably now stick the joint in the freezer until Sunday morning, when it will come out to be defrosted. I consider it unlikely that you expend more energy doing one weekly shop than you would were you to venture into the supermarket to buy only what you needed for the day ahead.
Similarly, surplus killing can only really be considered a waste of energy for a predator if they expend more energy killing prey individuals in a single ‘hit’ than they would killing the same number individuals over a prolonged period of time. Ergo, if a fox expends X calories killing 20 chickens in a coop, this act only represents a waste of energy if the same fox were to expend less than X cal killing one chicken per night over, say, 20 nights. The exception to this idea is if the fox is in someway prevented from eating its kills. If the fox is discovered before it can move all the chickens, or it’s cache of chickens is raided by another animal, then the energy expended by the fox to kill the chickens provides no benefit to the fox’s direct fitness and the surplus killing event could then be considered a waste of the fox’s energy.
Some might argue that there is the added energy “expense” of caching all this prey, which isn’t present if the predator killed only what it needed. This is certainly true. However, although the expense of caching 20 birds is reduced -- I shy away from ‘removed’ because leftovers from a single bird may well still be cached -- there is the added outlay of returning to the coop, gaining entry, chasing and killing another chicken.
The idea that surplus killing represents a waste of resources seems less likely when we consider that predators often bury (or cache) un-eaten food. Wildcats (Felis sp.), for example, have been observed to put the remains of their meals under logs; stoats (Mustela erminea) and mink (Mustela vision) larder cache, while pumas (Felis concolor) may scrape branches or leaves over a carcass, presumably in a bid to conceal it. Polecats (Mustela putorius) are also known to store frogs in their dens after biting the heads to immobilize them. Still, caching is not infallible -- have you ever cleaned out the kitchen cupboards or fridge and found food that has exceeded its “Best Before” date? -- and some cached food will invariably never be recovered.
Nonetheless, “waste” is a human economic term; in nature, nothing goes to waste. Another scavenging animal may discover food that has been cached and forgotten about and, even if the cache is not unearthed, there is a barrage of microorganisms (i.e. bacteria, fungi, Actinomycetes and protozoa) and creepy crawlies (e.g. worms, millipedes, sowbugs, ants and various beetles) that will decompose uneaten food. In time, even the skeleton will -- the very rare event of fossilization notwithstanding -- be reduced to unrecognizable components. The time taken for a corpse to decompose varies considerably with environment. According to Kenneth Iserson, in his book Death to Dust: What Happens to Dead Bodies, if you bury an adult human body about two metres (6ft) into the earth without any embalmment or coffin and in a temperate climate, only the skeleton will remain in about 12 years. If the body is put in water, decomposition takes about three years, while a body exposed to the air will decompose within about a year-and-a-half. This is interesting because it highlights how the place of caching is important when considering how long the food will remain in an edible condition. Hyenas (Crocuta crocuta), for example, are known to cache surplus food in shallow water and apparently have considerable success relocating, while leopards (Panthera pardus) tend to cache uneaten food in trees – these examples suggest that hyena and leopard kills would typically decompose faster than those of canids, which tend to bury surplus food.
So, three possible explanations have been put forth to account for the phenomenon of surplus killing – which is correct? Well, unfortunately, no single theory can suitably account for all cases. Indeed, there probably isn’t one universal reason to account for all instances of surplus killing. However, the observation that such events usually manifest where prey with an inability to escape -- through behavioural or physical inhibition -- is in abundance, suggests that surplus killing may, indeed, be the result of a hyper-stimulation of the predator’s killing mechanism. Whatever the reason, we have seen that there are both advantages and disadvantages to surplus killing. Among the disadvantages is the possibility that killing to excess will deplete a limited food source that may become essential in times of food stress. There is also the argument that surplus killing represents a waste of a predator’s energy (although caching seems to at least partially reduce this) and could lead to injuries or even death during the chase or kill. Conversely, the advantages include the possibility that a predator could consume the carcasses at a later date when hungry again, or that members of the same social group (including offspring) may benefit from the surfeit food. Alternatively, a predator may use the abundance of easy to catch prey to hone hunting skill that may prove useful in the future. (Photo: It is not always accurate to say that a fox can only carry one prey item at a time - here, a fox runs down an Alaskan highway holding a Ground squirrel, Spermophilus paryii, and a Snowshoe hare, Lepus americanus)
In conclusion, where anti-predator defence mechanisms have been lost (either through domestication, enclosure, or adverse weather conditions), prey animals are susceptible to significantly higher than normal mortality at the hands of a predator. It seems the presence of abundant prey that fail to flee causes an over-stimulation of the predator’s killing mechanism. In this regard, the act of surplus killing seems to be a very unfortunate natural response to an artificial or stochastic situation. The evolution of caching behaviour by predators goes some way to reducing the ‘waste’ otherwise generated by killing to surfeit, although caching is not infallible and caching invariably cannot utilise all surplus food. However, even if a cache isn't found by its owner -- or by another animal -- there is an army of microorganisms that will clean-up after a caching fox. (Back to Menu)
Q: You say on your fox page that Red foxes tend to scatter cache un-eaten food. The word “tend” implies that this isn’t always the case. Are there exceptions to the scatter cache rule and, if so, what are the benefits of scatter caching?
A: I should point out that the ideal of scatter caching is not so much a “rule” as conventional wisdom. If you look hard enough, there are exceptions to pretty much any “rule” in nature – it’s what makes biological systems so frustrating and, at the same time, so alluring! Indeed, not all fox species are known even to cache food – for example there is no evidence of food caching in the Blandford’s fox (Vulpus cana). Anyhow, although scatter caching seems more common than larder caching (or larder hoarding) both behaviours have been observed in Red foxes (Vulpes vulpes).
First, a little background. Caching seems to be a flexible behavioural response to a surfeit of food by a predator relying on prey whose abundance fluctuates considerably. J David Henry observed foxes as young as six weeks old caching food, suggesting some genetic predisposition to hiding leftovers. Conventionally, it was believed that larder hoarding was more efficient for territorial species -- because the larder would be clumped and located within the area of greatest activity -- while non-territorial animals would scatter cache (because scatter caches tend not to be defended). However, foxes -- which will defend their territory -- seem to employ scatter caching as the ‘norm’, with larder caching being the exception. (Photo: Very young foxes are well known to cache food, suggestions some genetic predisposition to do so)
Foxes are -- as a function of a small stomach and reduction in skeletal mass -- much lighter than canids of similar physical dimensions. The Irish terrier and English foxhound, for example, have similar physical dimensions to Red foxes, but are nearly twice the mass. Studies on the stomach capacities of foxes have shown that these animals have proportionally smaller stomach sizes compared to many other canids. For example, a Red fox can consume a maximum of about 10% of its bodyweight in a single sitting, while a Grey wolf (Canis lupis) may consume as much as 20%. As a result, the largest individual foxes are only capable of consuming a kilo of meat per sitting, with many of the smaller (more average-sized) individuals eating only half a kilo. Consequently, should a fox stumble across easily obtainable prey, the remains of a wolf kill, or some other bountiful source, excess food is carried away and buried for later use.
The type of cache foxes use, as well as the extent to which they attempt to conceal the cache, varies between individuals, improves with age and is related to both the availability of food and the ‘value’ of the food. In their book Urban Foxes, Steve Harris and Phil Baker note that the urban foxes of Bristol would often cache their quarry rather haphazardly, leaving feathers and wings sticking out from the ground. Conversely, in his 1986 book, David Henry reports that, of the hundreds of fox cachings he witnessed in the boreal forests of Canada, each site was carefully chosen and the caching process meticulously implemented – one fox was observed to walk backwards away from his cache hole, carefully erasing his footprints from the snow as he went! Indeed, it appears that the care with which food remains are cached is largely dependant upon the ‘value’ of, and the fox’s preference for, the food item. Foxes tend to cache high-value foods (such as meat) more carefully than they do lower value items (such as fruit, vegetables and cleaned bones). In a 1976 paper to the German journal Zeitschrift fur Psychologie, David MacDonald reported foxes caching preferred prey -- such as Field voles (Microtus agrestis) -- more consistently than less-preferred prey, like Bank voles (Myodes glareolus).
Most detailed observations on fox caching behaviour have revealed a tendency to scatter cache their leftovers. Economically, this seems to make good sense: don’t put all your eggs in one basket (or all your food in one hole)! During his many hours of fox observation in Canada, David Henry undertook a series of impressively ingenious experiments to assess the benefits of scatter caching. Henry wandered around the forests, burying small amounts of tinned dog food; first in a scattered pattern and then in a larder caching fashion. He made detailed maps and notes of where each hoard was buried and returned to each a short time later to see if any marauding animals had discovered the cache. Henry found that when he larder cached his meat, an average of six caches (out of his total of 15) remained, while seven of the scatter cached hoards (again out of 15) were still buried. These results didn’t suggest much until he calculated the standard deviation (a statistical indication of how much a set of numbers vary from the mean). It transpired that the standard deviation of the larder hoards was much higher than it was for the scatter caches (6 + 4.39 compared with 7 + 1.67). In other words, scatter caching doesn’t reduce the mean number of caches that are likely to be discovered by ‘robbers’; instead scattering makes these inevitable losses more regular, more uniform and ultimately more predictable. Ergo, it would seem from Henry’s results that scatter caching increases the chances that at least a portion of the caches will still be there when the fox needs it. (Photo: A fox leaves to cache a piece of meat)
So, taking Henry’s results into consideration, we have some idea why foxes may be more prone to scatter caching leftover food than hoarding it in a larder hole. However, larder caching does still occur. J Sande observed a Red fox in Sweden repeatedly putting prey into the same hole. Examination of the cache found it to contain a hare, ten field mice and a grouse. Similar observations of both Red and Arctic foxes on Baccalieu Island off Newfoundland by Bohdan Sklepkovych, currently at the University of Stockholm in Sweden, have shown larder-caching tendencies in both species. In a 1994 paper, Sklepkovych reports that seabirds -- especially Leach’s Storm petrels (Oceanodroma leucorhoa) -- captured and hoarded prior to the onset of winter composed the largest proportion of the Red fox’s winter diet. Indeed, a later study reported that Storm petrels made-up a minimum of 53% to 63% of fresh scat collected in February, despite the birds’ absence from the island between November and April.
A 1996 paper to the journal Arctic, Sklepkovych and his colleague, William Montevecchi at the Memorial State University in Canada, looked at food hoarding behaviour of Red and Arctic foxes on Baccalieu Island. The biologists concluded that larder hoarding was associated with a superabundance of food and that it appears to represent a flexible response to changing environmental conditions. In one example cited by Sklepkovych and Montevecchi, a larder discovered in 1985 had 16 holes and 385 out of the 396 (97%) carcasses inside were Leach’s Storm petrels! They observed both larder and scatter caches from their foxes, witnessing two distinct ‘types’ of larder hoard: (1) one or more holes naturally occurring or actively dug beneath boulders; and (2) several holes dug vertically into the soil to a depth of about one metre (3ft). Interestingly, no attempt was made to conceal the hoard at ground level, suggesting a superabundance of prey. Sklepkovych and Montevecchi also found that decomposition in the caches was often reduced -- the microclimate was noticeably cooler than the ambient -- and three freshly-killed petrels placed under a rock in July 1986 showed little sign of dehydration and were all well preserved when checked some four months later. (Photo: Not only do foxes possess a keen ability to recovered buried food, they're also good at finding other predator's left-overs)
So, we know that both larder and scatter caching are known in Red foxes and we know that scatter caching serves to make losses more uniform. However, what is the likelihood of a fox ever returning to its cache? Well, much of the data available suggest that foxes have a good spatial memory, aided by the use of urine and faeces to mark cache sites. In their 1996 paper Sklepkovych and Montevecchi found that of 67 petrels caught by two foxes, 22 (33%) were eaten, while all but two of the remaining birds were partially eaten before being cached in one of 45 scatter hoards. Of those cached, 12 (28%) were recovered within 24 hours, 17 (41%) within two days, 22 (53%) within one week, 26 (62%) within two weeks and 1 within three weeks. This suggests that at least 62% of the caches were recovered during the study period and, whether or not foxes subsequently recovered the remaining caches is unknown. Oxford University’s David Macdonald and three colleagues reported higher recovery rates in a 1994 paper to the Journal of Mammalogy. During their study in Dalyan, on the coast of Southwest Turkey, Prof Macdonald and his co-workers found that Red foxes retrieved 94% of scatter cached Loggerhead turtle (Caretta caretta) eggs (no larder hoarding was observed), 80% on the subsequent night.
Fox cache sites may be marked with either urine or faeces, apparently depending on their contents. In his book Red Fox: The Catlike Canid -- and in a 1977 paper to the journal Behaviour -- Henry notes that where foxes cache more durable items (like bones), they mark the cache with more durable scent (i.e. faeces). Generally, however, foxes will only mark caches after they’ve been emptied and, as such, he considered this urination to be a sort of ‘bookkeeping’ method. Henry observed that the foxes would urinate on the cache after the food had been recovered and consumed (or moved elsewhere), possibly to prevent the fox wasting time and energy looking for food that is no longer there. However, there did seem to be some ambivalence in this behaviour, because if the smell of food was still sufficiently strong, the fox would ignore the smell of urine and excavate the ground anyway.
In conclusion, although foxes scatter cache with greatest frequency, larder caching has been observed. Scatter caching appears to serve as a method for regulating losses of hoarded food to robbers, making any losses more regular and uniform. Where larder hoarding is observed, it appears to be a flexible behavioural response to a superabundance of available prey. (Back to Menu)
Q: Are Foxes Colour-blind?
A: The short answer to this is: probably not! First a little background. At school you were probably taught about something called the Electromagnetic Spectrum (or EMS), which represents the complete range of electromagnetic radiation, from the longest radio waves to the shortest cosmic waves. We call this range the “Electromagnetic Spectrum” because it is composed of electromagnetic radiation. We need not concern ourselves with what electromagnetic radiation actually is -- although it is basically radiation consisting of an electric and magnetic field that are at right-angles to each other and the direction in which they’re travelling -- but we should be aware that we can only see a small percentage of it. The wavelengths of light that we can see fall into the category of “Visible Light”.
We classify electromagnetic radiation based on its wavelength (see figure below). Wavelengths of radiation are measured in units called “nanometres” (abbreviated to "nm"); one nanometre is one thousand-millionth of a metre or, to put it another way, there are 10 million nanometres in a centimetre (or nearly 26 million in an inch). Visible light is radiation with a wavelength of between 380nm and 780nm – wavelengths between these values represent different colours of light. For example, light with a wavelength of 740 to 620nm is red, while that between 575 and 500nm is green.
We are able to see the world around us because our eyes pick up visible light reflected by objects in our surroundings; the colours we see are dependant on the wavelength of the reflected light. The stationary organizer on my desk, for example, appears red because it absorbs all colours of visible light except red, which it reflects. Light bounces back from objects and enters our eye through the pupil, striking the light-sensitive membrane at the back of our eye called the retina. In fact, during development of the embryo, part of the neural tube -- which goes on to develop into the central nervous system -- forms an outcropping, which extends and develops into the retina – the retina is consequently considered part of the brain.
Cells on the retina can be divided into two broad types: rods and cones. Rods are sensitive to very low levels of light, but are monochromatic (i.e. don’t detect colour), which is why in conditions of very low light (i.e. dusk and at night), we see objects in greyscale. Consequently, rod cell vision is often referred to as “scoptic” or “twilight” vision. The rod cells are also used for detecting movement. Conversely, cone cells are sensitive to bright light and colour. In the human eye, we recognise three different ‘types’ of cone cell, separated by their colour pigment: red (peak at 570nm); green (535nm); and blue (445nm). The colours we see are determined by which combination of sensors are excited and, because most humans have these three pigments, the human eye can sense almost any gradient of colour when red, green and blue are mixed.
The presence of three colour-sensitive pigments is referred to as trichromatic vision. Humans are not the only mammals with three cone types, cats as well as certain apes, chimps and African monkeys also have three colour-sensitive pigments. However, the presence of these pigments doesn’t necessarily mean that they see colour in the same way as humans. Although cats have three cone pigments, they have slightly different peak sensitivities, leading to a more pastel-coloured vision, with less saturation than humans can register.
There are some inherent pitfalls in trying to assess the presence of colour vision based solely on the number of colour-sensitive (cone) cells on the retina. Moreover, there is the problem that colour is highly subjective - I might call something red, while you might think that it was pink and someone else might plump for orange! Generally, psychometric tests are also needed to assess the colours that animals are able to see and respond to. However, although the psychological experiments have yet to be applied to foxes, studies on their retinal topography -- that is to say, studies looking at the type and distribution of cells on the retina -- have shown that foxes certainly have the ‘equipment’ to register some colour, although the degree to which foxes (and dogs in general) are able to resolve colours is probably less than ours. Indeed, given the roles that dogs play in our daily lives (perhaps most importantly as guide dogs), it is something of an oddity that there are so few studies looking at the vision of canids – many of those that do exist have produced dubious or conflicting results.
Observations on the activity patterns of canids do suggest that they are “visual generalists”, able to work in conditions of various light intensities. For example, I’ve just returned from walking our dog – the weather is bright and sunny and she chased anything that moved as we meandered around the forest. Similarly, anyone who has taken their dog out at dusk or at night can vouch for the fact that, while they may not be able to see the path they’re walking on, their dog is off investigating the undergrowth. Observations of fox movements suggest that they are able to cope with a wide variety of light conditions; foxes are active during dawn, daytime, dusk and throughout the night.
Although foxes and other wild canids are known to be arrhythmic (i.e. active during the day and night), much of their hunting and foraging occurs from dusk to dawn and, as might be expected, studies on canid retinas have revealed a predominance of rod cells (about 97% in dogs and wolves), suggesting that their sight in dim light and ability to differentiate shades of grey and movement is superior to ours. In a 1993 study published in the journal Visual Neuroscience, a team at the University of California looked at the photopigments (i.e. light-sensitive chemicals) of dogs and foxes. The optometrists found that all the canids in their study possessed two cone pigments, one with a peak sensitivity of about 555nm (light green) and another with a peak between about 430 and 440nm (dark blue / purple). In the Red fox (Vulpes vulpes), this second (short-wavelength) peak was at 438nm. These findings imply that foxes have dichromatic (i.e. two-colour) vision similar to that of a human deuteranope – in other words, it suggests that foxes are red-green colour blind.
Studies on the distribution of rod and cone cells on the retina’s of canids has shown that, although some species do apparently show an increase in cone density towards the centre of the retina, dogs do not have a fovea (the region on a human retina composed entirely of cones that you’re using to read this article). The lack of a fovea suggests that a dog’s ability to discriminate details is less than ours. Indeed, some authors have estimated that a dog’s eye for detail is about six times worse than ours. Similarly, a recent study by a team of biologists at the University of Vienna reported that brightness discrimination ability in dogs is about two-times worse than in humans.
Thus, in conclusion we can say that foxes -- and dogs in general -- are not colour blind; they possess dichromatic vision that effectively makes them red-green colour blind. The lack of a fovea in canines also implies that humans are able to discern details twice as well as dogs. However, dogs do have a significantly better ability to discriminate between shades of grey than humans, coupled with a capacity to detect movement and see objects in conditions of dim light (thanks to a reflective tapetum) that’s superior to ours. (Back to Menu)
Q: I have taken in an injured fox cub and would like to keep it as a pet – is this illegal?
A: In short, no, in Britain it is not illegal to keep a Red fox (Vulpes vulpes) as a pet. It is, however, ill-advised.
During the late 1960s and early 1970s, the UK experienced a trend of people keeping exotic animals (including various hybrids) as pets; this fuelled a growing concern for public safety. On the 22nd July 1976, UK Parliament voted in “An Act to regulate the keeping of certain kinds of dangerous wild animals”. The legislation was called the Dangerous Wild Animals Act and, under section 5, it prohibits the keeping of “any dangerous wild animal except under the authority of a licence granted in accordance with the provisions of this Act by a local authority.” Chapter 38 of the Act sets out a list of the animals for which a licence must be obtained; it covers various species of bird and mammal, along with the crocodilian reptiles, snakes and several genera of lizards, spiders and scorpions. Among the mammals, the list covers all of the Canidae (dog family), with the exception of the foxes (genera: Alopex, Dusicyon, Otocyon, and Vulpes), Raccoon dog (Nyctereutes procyonoides) and, of course, the domestic dog (Canis familiaris). To this extent, one could freely keep a fox as a pet without the need to obtain a licence from your local council.
The fact, however, that a licence isn’t required to keep a Red fox does not mean that you are without any legal obligation. Foxes brought into captivity fall within the constraints of the Protection of Animals Act of 1911 (with various amendments). Under this legislation, it is a criminal offence to cause “unnecessary suffering” to any animal in your care – this can include a failure to provide suitable food, water, shelter or veterinary care. Successful conviction under this Act can result in a £5,000 fine, up to six months in prison, or both. Additionally, any animal under the care of a human falls within the remit of the Animal Welfare Act of 2006 – the act created in November 2006, but didn’t become law in the UK until April (March in Wales) of 2007. Sections one and two consider a person to have committed an offence if "an act of his, or failure of his to act, causes an animal to suffer"; this means that even watching someone else cause an animal 'unnecessary suffering' and failing to do something about it is treated as an offence under this Act. Section nine of the Act set out the duty of care a person has towards an animal in their care, stating that:
"A person commits an offence if he does not take such steps as are reasonable in all the circumstances to ensure the needs of an animal for which he is responsible are met to the extent required by good practice."
The Act considers "an animal's needs" to include:
- its need for a suitable environment
This legislation also covers the mutilation of animals, causing animals to fight and even tail-docking of dogs. In addition to fines (up to £20,000) and prison sentences (up to one year), Section 35 of the Act states that any person convicted under the legislation can be disqualified from owning, keeping, or participating in the keeping of animals. The Protection of Animals Act and Animal Welfare Act work in conjunction with a third law, the Abandonment of Animals Act, which we shall look at in a moment.
Despite being legal, keeping previously-wild foxes -- those bred and sold by the pet trade are a different case -- as pets should be strongly discouraged. Raising a rescued wild fox is not the same as caring for a domestic dog. Foxes can be very boisterous and destructive as they grow. They will require some form of containment (i.e. a cage or pen) in order to prevent/minimise potential damage to the house or garden and have a considerable amount of energy (they’re almost insatiably curious), which must be taken into consideration. The extremely potent anal gland secretion and urine, which are employed as scent marking along the boundaries of the animal’s territory, mean that foxes can also smell strongly. It is possible to have the anal glands surgically removed and/or have the animal spayed or neutered (the latter an attempt to modify the fox’s behaviour), although such operations rarely achieve the desired result. Foxes can be very difficult to house-train and, while they can be trained -- as one would a dog -- to a limited extent, levels of obedience can be considerably lower than for domestic dogs, which have been selectively bred for their servile demeanour.
The provision of veterinary care is a consideration that must be addressed to ensure the fox remains healthy. Most veterinarians in the UK are probably capable of dealing with a fox – many already deal with wildlife casualties and, I suspect, most would treat a fox as though it were a domestic dog. The fox would need to be vaccinated against the various diseases contracted by domestic dogs, including canine distemper, Leptospirosis, infectious canine hepatitis, rabies and canine parvovirus (or ‘parvo’). The latter of these is a highly infectious disease caused by viruses of the Parvoviridae family that typically manifests in two forms: intestinal parvo (which attacks the immune system, destroying rapidly dividing cells such as those in the lymph nodes and bone marrow) and the less common cardiac parvo (which, as the name suggests, attacks the heart). Dogs can contract the virus through contact with infected surfaces and material, including infected faeces and soil. Thus it is important to ensure a pet fox, just like a pet dog, is vaccinated against parvo. Between 1991 and 1995, a team of biologists led by Uwe Truyen at the University of Munich’s Institute for Medical Microbiology collected blood sera from Red foxes in Germany to test for canine parvovirus, canine distemper virus, canine adenovirus and canine herpesvirus. The biologists found that 65 (13%) of the 500 samples they collected tested positive for parvo and, in their 1998 paper to the journal Epidemiology and Infection write that:
“… the sudden emergence of canine parvovirus in the domestic dog population may have involved the interspecies transmission between wild and domestic carnivores.”
Thus, foxes can contract parvo from domestic dogs and dogs can invariably catch parvo from foxes – especially when we consider that many dogs display a penchant for rolling in fox scat.
I have heard stories from people in Britain who have kept foxes as pets, which suggest these animals can make excellent companions. In some cases they probably do. However, there are also many cases where they invariably fail to live up to their owner’s expectations and are either given up to a wildlife centre, dispatched or abandoned. In the UK (excluding Northern Ireland), the Abandonment of Animals Act (June 1960) makes it a criminal offence to leave an animal "in circumstances likely to cause the animal any unnecessary suffering". While one might be inclined to argue over the term “unnecessary”, abandoning an animal that is unable to ‘look after itself’ is treated as an act of “cruelty” as set out by Section 1 of the 1911 Protection of Animals Act. Unfortunately, cases of pet foxes being abandoned are not uncommon. To the best of my knowledge there are no official figures on the number of foxes kept as pets in the UK, or the number abandoned each year, but Vale Wildlife Hospital and Rehabilitation Centre founder and manager, Caroline Vale, told me:
“… every year we have to take in at least one cub that has been hand-reared and then discarded when it gets older and starts to smell or becomes aggressive.”
Indeed, on their website, Vale Wildlife Rescue has short profiles of several foxes that have been taken in after apparently being kept as pets before being dumped. Seven-year-old dog fox “Bart”, for example (photo, left), was taken in by the centre after being found wandering in Birmingham’s Sutton Park wearing a collar.
A big problem for Vale, and many other rescue centres, is that foxes taken in as cubs and raised to adulthood as pets often become imprinted. Imprinting, as Arizona State University’s John Alcock describes it in his 2005 book Animal Behavior, is the process by which: “a young animal’s early social interactions, usually with its parents, lead to its learning such things as what constitutes an appropriate sexual partner”. Imprinting, which is now often lumped together with what behaviourists refer to as “associative learning” (despite the latter generally involving a reward), was first described by ethologist Konrad Lorenz. In his 1952 book, King Solomon’s Ring, Lorenz described how he was able to imprint himself on greylag goslings (Anser anser) such that they followed him everywhere thinking that he was their parent.
Numerous studies, especially on birds, have shown that when animals fostered by a different species reach sexual maturity, they typically try to mate with members of the fostering species. Between 1998 and 2000, for example, a team of biologists at the University of Oslo in Norway led by Tore Slagsvold studied the effect of cross-fostering on Blue tits (Cyanistes caeruleus) and Great tits (Parus major). The researchers put blue-tit eggs into great tit nests and vice versa – actually, they put the eggs into Coal tit (Parus ater) and Pied flycatcher (Ficedula hypoleuca) nests too, but it’s the Great tits we’re really interested in. The male great tits raised by blue tits tried to pair with female blue tits, while blue tits found mates with other blue tits, regardless of the species that fostered them. These data provide a superb example of how imprinting can have different consequences for different species. Recent neurological studies of imprinting have suggested that it may be a two-stage process: there is a ‘critical period’ during which the initial imprinting occurs, followed by a period of stabilisation (involving courtship attempts) during which morphological changes are made to some of the neurones. Regardless of the science behind it, the problem of imprinting can be a significant one, as Caroline Gould went on to explain:
“Whether or not an imprinted cub can be released depends on exactly how imprinted it is. If it is passed on to us when it is under 6 months or so old, then it will almost certainly revert once mixed with other wild cubs, but when we get them at, for example, 12-18 months old, which is not uncommon, it is virtually impossible to get them back into the wild and then they do have to spend the rest of their lives in captivity (or the alternative is euthanasia).”
In the end, while you may not be in breach of any laws -- and I should point out that the above applies only to the UK and the situation is different elsewhere in the world, so please check with your local authority -- I would urge you to think very carefully before you attempt to take on a fox as a pet. Perhaps arrange a visit to your local wildlife rescue centre, which will be able to provide a first-hand account of what it’s like raising a fox. Similarly, should you come across a fox in need of your help, the advice would always be to take it to your local wildlife centre – if you want to offer your help and support, consider donating something towards its upkeep or sponsoring its rehabilitation. Please remember that caring for any animal is a serious commitment and should not be undertaken lightly. (Back to Menu)
Q: When and how did foxes come to live in our towns and cities?
A: Contrary to popular misconception (recently reported in a documentary on urban foxes), the ‘phenomenon’ of the city fox is not particularly new and foxes have been present in some of Britain’s towns and cities for at least 80 years.
In 2001 a team of biologists at the University of Zurich in Switzerland, led by Sandra Gloor, proposed two hypothetical explanations for the presence of foxes in built-up areas: the Population Pressure Hypothesis (PPH) and the Urban Island Hypothesis (UIH). Basically, Gloor and her colleagues suggested that urban foxes were either intruders forced out of adjacent rural areas by the high population density (the PPH), or that they can breed in and colonize human settlements because they have adapted to the conditions of the urban habitat (the UIH). In other words, the PPH states that urban environments are suboptimal habitats for foxes -- that is, foxes live there because they have to, not because they want to -- while the UIH predicts the opposite.
In Britain, early theories on how foxes came to colonise cities revolved around the PPH; these urbanites were considered over-spill from the countryside. Some suggested that the outbreak of World War II in 1939 led to a decline in gamekeepers on country estates and, in the absence of control, fox numbers increased beyond the capacity for the countryside to absorb; the result was that dispersing individuals started moving into towns looking for food and shelter. An alternative theory, although along the same vein, implied that the Myxoma virus was responsible. The Myxoma virus causes the fatal disease myxomatosis (Myxo from the Greek muxa, meaning “mucus”) in rabbits and was responsible for widespread mortality in rabbit populations following its discovery in Uraguay during 1896. The disease spread throughout Europe after being inadvertently released on a private estate in France during and June 1952 and illegally released into the wild rabbit population on an estate in West Sussex during the autumn of 1953. Two years later, in 1955, it was estimated that some 95% of Britain’s rabbits had been killed. There are minor variations to the theory of how this affected fox populations, but in general it was thought that the virus’ introduction caused a superabundance of prey -- in the form of dead and dying rabbits -- that sparked a dramatic increase in fox numbers; once all the rabbits had gone, however, there was insufficient food to support such a large population and starving foxes started ‘invading’ towns looking for food.
So, which theory is correct? The short answer is: probably neither. Despite having data suggesting that there was a rise in fox numbers shortly after the introduction of the Myxoma virus, all available evidence indicates that the foxes switched from rabbits to voles once the latter were gone. Nobody knows precisely when the first fox set foot in a town, but the problem with ascribing the incursion to either lack of control during the war or a lack of food following myxamatosis is that there are records of urban foxes dating back to before war broke-out and at least two decades before myxomatosis arrived. There are reports of the occasional fox from Hampstead Heath dating back to 1912, although they weren’t seen with any regularity in the city until the 1930s. Indeed, writing in his 1937 A History of Richmond Park, Cyril Collenette told of how he often encountered foxes in Richmond Park in the 1930s and noted that 116 had been shot there during “the past six years”. In their 1982 summary of urban foxes, David Macdonald and Malcolm Newdick noted that foxes were known from Richmond Park during the 1930s. Similarly, in his seminal paper to the London Naturalist during 1967, Bunny Teagle described the appearance and spread of foxes in the suburbs of London, listing additional -- albeit sporadic -- records from the 30s, including one fox that was a regular sight in Kensington Gardens during 1938. Teagle wrote:
“[foxes] became more familiar animals to the human residents of the [Hampstead Heath] district from the early 1930s onwards…”
So, if foxes weren’t driven into towns and cities in search of food, how else might they have made the transition? In some cases it may not have been the foxes that made the first move; we may have come to the foxes rather than the other way around. (Photo: Contrary to popular misconception, foxes didn't start living in cities because they were starving and the recent introduction of wheelie bins hasn't caused them to starve. That said, the practice in some areas of leaving bin bags out and fortnightly refuse collections may have benefitted foxes).
I have heard people say that they’d be happy if all the urban foxes ‘went back to the countryside where they belong’. An important point to remember, however, is that our towns and cities were the countryside that foxes were in before we built upon the land. Indeed, several authors have suggested that urban fox populations have arisen simply because as humans built on Greenfield sites these animals, unlike a considerable number of other mammal species, didn’t move away; instead they adapted to their new surroundings and thrived. Martin Hemmington provided a potent example of this in his fascinating 1997 book Foxwatching: In the shadow of the fox in which he recounted the story of a fox earth he had been studying. The earth was situated in a country setting, nestled in a hedge under some trees and Hemmington described the changes he witnessed:
“Then disaster struck. Planning permission was given for a housing estate of over one hundred and fifty houses. Soon the area of which I had grown fond was barren. The regular fox paths had been replaced with tarmac; the rabbit warren was flattened, and the trees and hedges which used to conceal the earth were cut down. My countryside retreat became a concrete jungle.”
Ccontrary to Hemmington’s initial fears, however, the foxes didn’t move away; instead they remained and thrived. He continued:
“Within a very short time the householders in this area started asking why foxes, which belonged in the countryside, had started to invade their streets and gardens and had chosen earths under garden sheds to give birth! In fact the foxes were the original residents and the people invaded their territory.”
Hemmington’s experience was far from unique and it is now widely held that many urban fox populations may have arisen when so-called ‘urban sprawl’ began replacing large areas of the countryside. Indeed, this was considered a plausible explanation during the 1970s and, in his Red Fox, Huw Gwyn Lloyd wrote:
“The first irruptions of urban foxes were probably due not so much to an influx of foxes as to extensive housing development in the suburban fringes in the 1920-40 period.”
Stephen Harris and Jeremy Rayner provided some statistical support for this idea in a paper to the Journal of Animal Ecology during 1986. Using a statistical method of grouping related variables (called a discriminate analysis)Harris and Rayner demonstrated that local fox densities in 157 towns in England and Wales were best explained by the proportion of owner-occupied housing situated away from industry. The biologists proposed that the boom in private house construction after 1930 (largely the result of increased mobility allowing people to live and work further apart) led to a proliferation of privately owned three-bedroomed semi-detached houses; these middle-class suburbs had low-density housing, with quiet residential roads and medium-sized gardens. It appears that these areas provide foxes with exactly the type of habitat foxes favour and the authors wrote:
“…it is probable that during the inter-war years the piecemeal development of many cities, engulfing tracts of rural land which were only later developed, gradually forced the foxes to live in closer contact with man.”
Invariably the progressive urbanization of countryside cannot explain every population of urban foxes and there were almost certainly cases where populations arose following the incursion of rural animals into towns and cities. Indeed, the radio-tracking of foxes since the mid-1970s has demonstrated that animals living on the edge of human settlements may move into the towns or cities to forage at night, although some populations are more willing than others to walk our streets. In their contribution to the second European Ecological Symposium (published in 1982), David Macdonald and Malcolm Newdick point out that, while foxes radio-tracked in Oxford move in and out of town, those in the north of England conspicuously avoid towns; the authors also made the point that in continental Europe rabies epizootics move around, rather than through, human settlements. In light of the Bristol analysis, it seems likely that the behaviour of the northern foxes may reflect less desirable housing (i.e. more council-owned properties situated closer to industry). At any rate, there can be little doubt some urban colonizers were rural foxes that either gradually spent more time on the urban peripheries or were raised in rural areas and dispersed into nearby suburbs. Once established at the periphery the population can begin spreading into suitable urban areas; not only do urban foxes tend not to move very far (presumably because they don’t have to), there are some tracking data to suggest those born in urban areas may prefer towns to rural landscapes. Indeed, Harris elaborated on the scenario in his 1986 book Urban Foxes in which he described how foxes colonize cities in two stages: they established themselves on the fringes first, before spreading into the city centres. (Photo: Central and West London as seen by the SPOT Satellite. Picture from WikiCommons).
So, there is no evidence that foxes were forced into our cities from the countryside; instead they have either chosen the cityscape or it is us who have forced our cities into their countryside. Now they are here there is little likelihood that they will leave – after all, why would they? Foxes are supremely adaptable mammals and many urban and suburban habitats provide ideal living conditions for them. Humans as a species tend to be rather wasteful – the British government estimate that 7.3 tonnes (equating to roughly GBP 12 billion) of edible food is discarded every year – and foxes are perfectly placed to capitalise on this. In addition, food is deliberately put out for them in many backgardens (in Bristol it was estimated that about 10% of the population regularly put food out for foxes) in some cases to excess. (Back to Menu)
Q: Are urban foxes unique to Britain?
A: No, although this was once thought to be the case and in his opus on Red fox natural history, H. Gwyn Lloyd wrote that: "In Europe the urban fox is almost unique to Britain". Nonetheless, colonisation of cities outside of the UK seems to have been more recent and almost disjointed when compared to Britain. Within the past three decades, urban foxes have colonised several European cities, including Paris (France), Rome (Italy), Stockholm (Sweden), Oslo (Norway), Berlin and Stuttgart (Germany), Zurich and Geneva (Switzerland), and both Copenhagen and Aarhus (Denmark). Colonisation of European cities appears to have started during the 1970s and 1980s and has progressed rapidly. In Switzerland, for example, foxes were first observed to be breeding in some cities during the early 1980s and by 2004 all thirty cities with populations in excess of twenty thousand people had been colonised by foxes. In 2002 it was estimated that Zurich had more than ten adult foxes per square-kilometre, which is a density higher than any recorded in the Swiss countryside.
Outside of Europe, urban foxes are also found in the U.S.A (including Los Angeles, New York and Washington), Australia (Adelaide, Brisbane, Canberra, Melbourne and Sydney), Canada (Toronto) and Japan (Hokkaido and Sapporo); in many of these locations colonisation has occurred within the last twenty years. The exception seems to be Australia. Colonisation of some Australian cities began around the same time as in British cities, with records of foxes in Melbourne, for example, dating back to the 1930s. It should also be mentioned that, although still referred to as ‘urban foxes’, populations living in back gardens and city centres are comparatively rare outside of the UK. In Rome, for example, Bruno Cignini and Francesco Riga (both at Italy’s National Wildlife Institute) found that foxes were generally found only in city districts with a high percentage of ‘green’ areas. Similarly, in Toronto, Christine Adkins at Queens University in Canada and Philip Stott at Adelaide University found that, even though foxes were tracked in the settlements, they spent most of their time in the extensive areas of natural vegetation in the ravine, or in other well-vegetated patches; they found no evidence that the animals were scavenging human refuse.
Few cities outside of Britain have documented the colonisation and spread of foxes, or the public attitudes to these vulpine residents. Indeed, there is nowhere in the world where urban fox populations have been studied for longer or in greater detail. Switzerland and Denmark are probably a close second to the UK and the colonisation of cities in Denmark has been well documented; a summary was provided by Sussie Pagh at the Aahus Museum of Natural History in a paper to the journal Lutra in 2008. According to Pagh, foxes have been seen in and around Copenhagen since the time of the Slesvig Wars (1848 – 1850), where they apparently denned in the soldiers’ embankments. It seems that fox numbers increased dramatically thereafter and by 1860 they were apparently so numerous in the Frederiksberg Garden (Photo below), in the west of the city, that they “almost undermined the Chinese Pavilion”. During the 1960s fox numbers were also high and, in 1963, naturalist Hans Hvass wrote of foxes regularly being sighted in built-up areas and showing little or no fear of humans. Little appears to have changed during the subsequent twenty years and Pagh notes how, from 1980 onwards:
“… the foxes of Copenhagen have received increasing media attention, with articles about fearless foxes entering gardens and houses.”
There are still occasional reports of ‘brazen’ foxes in Copenhagen and Aarhus passing close by people without showing any apparent fear, although populations are estimated to have declined by some 50% to 60% following an epidemic of sarcoptic mange in Denmark. So, in conclusion, urban foxes are not the preserve of Britain; they are found in cities throughout Europe and beyond, although the population structure and relationship with rural groups appears to be different to Britain. In many countries outside of the UK the relationship between foxes and their human neighbours is very different owing to the threat of disease, especially rabies. Indeed, Red foxes are the principle vector for rabies in Continental Europe and North America. Fortunately, Britain remains rabies-free and this has permitted the unsurpassed in-depth study of urban foxes. The result has been some fascinating and unique insights into how wild mammals can respond and adapt to their surroundings. (Back to Menu)
Q: Are fox populations increasing in Britain?
Short Answer: There is no simple or straight forward answer to this question because there is no regular census of fox populations anywhere in the world. The UK's population of Red foxes is still in a state of flux following a mange epidemic in the mid-1990s, during which an estimated 95% of some urban populations were believed to have died. The best evidence we have suggests that while rural populations have remained stable since at least 2002, urban fox numbers are probably rising as populations recover from the mange epidemic. There is also likely to be a discontinuity in any population changes -- that numbers will be increasing in one part of the country and declining in another -- but there is nothing to suggest that numbers have reached pre-mange levels yet. Contrary to popular misconception, there is no evidence that fox populations have ‘exploded since the ban’. Indeed, there are no data to suggest that the 2004 Hunting Act (which made it illegal to hunt foxes on horse-back with dogs) has had any significant impact on national fox numbers; it appears that any slack left in the wake of the hunt was taken up by farmers shooting or trapping foxes.
The Details: Monitoring animal populations, especially species that tend to be nocturnal and rather secretive is a difficult task and, until relatively recently, there had been no attempt to census fox populations at the national level. So, what’s the problem with counting foxes? Many of us see them everyday and in some cases they have become so accustomed to human presence that, even in relatively busy locations, they can be seen out during the daytime. Surely simply counting them shouldn’t be too much of a challenge? Well, as the former M.A.F.F. biologist H. Gwyn Lloyd pointed out in his 1980 book, The Red Fox, it’s actually more difficult than it may first appear because fox:
“numbers are low and its ranges large by comparison with those of voles, rabbits or hares, for example. Inevitably, therefore, the counting of foxes involves a great deal of manpower and effort.”
Indeed, a count of all the individuals in a given area (known as a direct census) is usually very expensive and largely impracticable, so we need to look at other methods; without a direct count, however, any method would only provide an estimate of numbers. Indirect censuses are often used, including the capture, tagging and recapturing of individuals in the area, or estimating the amount of available food and calculating how many animals that could support, but these are time consuming, often unreliable and, in the case of the former, limited by season (it must be done during the spring and summer when foxes are at their most sedentary). Common indirect censuses involve attempting a count of all the animals in a small area and then use an understanding of the animal’s biology to extrapolate up to a larger area, or to use game-bags (the number of animals killed by game-keepers). Game-bags are a convenient source of fox numbers and in the 1992 Game Conservancy Trust report Game heritage - an ecological review from shooting and gamekeeping records, Stephen Tapper noted how game-bags for all ten regions of Britain showed a steady increase in the number of foxes killed per unit-area between 1960 and 1990, with the largest (seven-fold) increase being in south-east England and the smallest (two-fold) increase in Scotland. Unfortunately, the number of foxes killed by game keepers does not always reflect a true change in population density; the numbers killed varies with effort, which is related to perceived threat to game. Consequently, more foxes killed do not necessarily equate to more foxes being around – it could equally be that culling efforts have intensified.
A third option is to use field signs and relate their frequency to the number of animals in the area – these are called population indices and are technically a form of indirect census. Population indices are among the most widely used methods of estimating animal populations, although they’re not without their problems. Indeed, in a 2004 paper to the journal Mammal Review, Linda Sadlier and colleagues at the University of Bristol assessed the use of field signs as a method of monitoring populations of Red foxes and European badgers (Meles meles). The biologists concluded that:
"At present, there is no single proven reliable method for monitoring changes in the absolute density of either foxes or badgers on a national scale..." and "...indirect methods [field signs such as scat and den counts] can only be used to measure relative changes in animal density in the same region over time."
It has been widely demonstrated that the number of animals killed on the roads, the number of tracks in an area, distribution of scats in an area, spotlight counts et cetera can all be used to estimate numbers for various species, including foxes – between 1969 and 1973 Steve Allen and Alan Sargeant used the number of foxes spotted by postmen to estimate fox numbers in six rural North Dakota towns. As we shall see, the most recent attempts at a national fox survey used the distribution of scats, which works well in rural habitats, but is problematic in that it -- along with many indices -- isn’t applicable to urban areas. There is, however, an index that seems relatively robust at estimating numbers in both urban and rural areas: the counting of breeding earths. The basic premise is that foxes live in family groups and raise a single litter of cubs per year, so each litter represents a single family. If one assumes a basic family unit is comprised of a dog, a vixen and a couple of subordinates (young from a previous year), it is possible to obtain a rough estimate of the number of foxes in the area based on how many family groups there are. Finally, we simply divide the number of foxes by the size of our survey area to get the density. It sounds rather crude, but it is surprisingly effective and since its first application in Russia in 1941, it has been widely used. In May 1974, for example, Forestry Commission biologist Hugh Insley used a survey of breeding earths to estimate the fox population density in the New Forest in Hampshire. Dr Insley used counts of 53 randomly selected squares and extrapolated up, based on the habitat, to arrive at a fox population of just under 600 animals (or a density of about two foxes per square-kilometre of Forest). Similarly, in the USA, biologists have used the technique to estimate fox numbers living on the plains. Despite being of local use, it is difficult to coordinate sufficient surveys to do this on a national scale, so an alternative approach is necessary. The first such approach involved using a system of classifying environments based on the type of habitats they include (called land class habitat mapping), developed by the Institute of Terrestrial Ecology (ITE) in Cumbria during the mid-to-late 1970s.
Town fox, Country fox
In 1995 the Joint Nature Conservancy Council published A Review of British Mammals, a 183 page report co-authored by Stephen Harris, Pat Morris, Stephanie Wray and Derek Yalden and giving details on the population trends of 64 species of mammal. In the Carnivora section, the mammalogists used data on the number of barren (i.e. non-breeding) vixens and itinerant foxes (those without a territory) in an ‘average’ population as well as data collected during Prof. Harris’ studies on urban fox densities during the mid-1980s (see below) to provide a more accurate estimate of the national fox population. Interestingly, despite introducing more factors into the calculations, their values were close to that of the 1981 appraisal – they estimated a total breeding population of about 240,000 animals. Of these, almost a quarter of a million foxes, it was estimated that 195,000 were in England, 23,000 in Scotland and 22,000 in Wales (no estimate was made for Ireland). This report represents the first attempt at estimating the number of urban foxes, suggesting that about 33,000 (roughly 14%) of these foxes were living in towns and cities (30,000 in England, 2,900 in Scotland and 100 in Wales). The authors pointed out that, assuming a mean litter of five cubs, each summer the population will swell to around 665,000 (with the birth of some 425,000 cubs), but the mortality rate is equivalent to the birth rate, meaning that the population is back to 240,000 by the following winter. Subsequently, there were several attempts made to estimate rural fox abundance in various parts of Britain during the early 2000s, but no further estimates of the national population were published until the mid-2000s.
The most recent attempt to assess national fox numbers came in the form of a survey overseen by Bristol University biologists and carried-out by volunteers. Between 1st February and 17th March 1999 and 2000, volunteers were allocated rural areas across the country; each site was visited and a pre-defined path walked, noting habitat characteristics and the locations of any fox scats before removing them for disposal. A couple of weeks later the route was re-walked and scat positions marked again, but this time the faeces were collected and sent to Bristol for dietary analysis. In total 444 one kilometre squares from around mainland Britain were surveyed and, using food consumption and defecation rate information from captive foxes, it was possible to estimate fox numbers. The results of the survey were published in a 2004 paper to the Journal of Animal Ecology by Charlotte Webbon, Phil Baker and Steve Harris. In congruence with the 1995 estimates, these data agree closely with the original 1981 figures. The data show that the mean fox density varied from 0.21 to 2.23 foxes per sq-km, depending upon habitat (with some of the highest densities in western England and eastern Scotland), resulting in a total rural fox population of 225,000 – this number increased to 258,000 when the 33,000 urban foxes estimated in 1995 was added. In 2002, 160 of the squares were re-surveyed in order to assess whether the temporary ban on fox hunting that resulted from an outbreak of Foot and Mouth Disease had any impact on fox numbers. The results, published in a report to the RSPCA and IFAW and a paper to the journal Nature during 2002, showed a significant increase in the number of scats in eastern England and a significant decrease in southern England, with all other areas showing no change – overall, there was a decline in faecal density of some 5%. The conclusion of the report was that the ban on hunting had no effect on fox numbers in Britain.
In 2004 the Hunting Act was passed into law and concerns were raised that removing this source of fox control from the countryside could lead to an ‘explosion’ in fox numbers. In a bid to find out, just over half (252) of the original squares were re-surveyed -- along with 139 new squares -- during the winters of 2005 and 2006. The results, published as the National Fox Survey 2005/2006 Newsletter, were similar to those of the 2002 survey, with an increase in fox density in eastern England and a decline in southern England. Broadly-speaking, fox droppings increased in almost half the squares, and declined in the other half (only 7% were unchanged). The conclusion of the Bristol biologists was that:
“At a national level, fox density was not different between the two surveys. Therefore, it appears that neither the Hunting Act nor sarcoptic mange have had an effect on fox populations in rural areas.”
In addition to the foregoing, there are a number of year-on-year surveys that have been recording the occurrence of foxes, as well as other mammals – these include the National Game-bag Census (NGC), Breeding Bird Survey (BBS), Waterways Breeding Bird Survey (WBBS), Winter Mammal Monitoring (WMM) and Mammals on Roads (MoR). The surveys haven’t been running for long enough yet to provide any clear trends, but preliminary results (the most recent results were published in 2008 by the Tracking Mammals Partnership) are interesting. The NGC has recorded a long-term (25 year) increase in fox numbers of some 71%, but data for 1995 to 2002 for 616 estates showed no significant change. The WBBS shows no significant change in fox sightings on their survey squares, while the BBS shows stable numbers between 1995 and 2001 and a decline between 2002 and 2007. Published data for foxes from the MoR (2001 – 2003) show a slight increase in numbers, with the largest rise in Wales (there are more recent, unpublished data, from this survey but I am awaiting confirmation from the People’s Trust for Endangered Species and will update this section once I receive the information). Overall, in their 2005 UK Mammals: Species Status and Population Trends, the Tracking Mammals Partnership wrote of Britain’s foxes:
“It seems there has been a long-term upward trend for this species, which has stabilized in the last few years.”
The city fox phenomenon
In a series of papers to the Journal of Animal Ecology during 1986, Stephen Harris and Jeremy Rayner described how they used questionnaires circulated to local councils and school kids -- who were asked to report sightings of fox earths -- to estimate the number of foxes living in Bristol. In the mid-1980s there were 211 family groups in Bristol, so 211 dogs, 211 vixens and 74 non-breeders, equalling almost 500 adult foxes in the city. When the method was applied to cities elsewhere in the country, it revealed concentrations of fox populations along the south coast, around London, central England and a belt across the English-Scottish border. Subsequently, estimates were produced for new UK towns and, by combining all the data, the 1995 estimate of 33,000 urban foxes was made, although at the time the impact of mange had yet to fully reveal itself. Six years later, in 2001, following the devastating mange epidemic, David Wilkinson and Graham Smith at the Central Science Laboratory in York published a short paper in Mammal Review, in which they presented a preliminary survey of changes in urban fox densities in England and Wales. Between May and November 1997, the researchers sent a questionnaire to 139 councils and 44 local mammal groups asking whether they thought urban fox densities had increased between 1986 and 1997; 156 (85%) responded and 41% thought fox numbers had increased, 42% thought they had remained the same, while 7% believed they had decreased. Care should be taken when interpreting the data because councils were responding based on complaints received from the public, but there was a distinct clumping of respondents from the London area who reported an increase in numbers, while most south-coast regions reported no change.
The most recent estimates from Britain suggest that, even by the mid-2000s, Bristol’s urban fox population was only about 30% of the pre-mange densities, but the dramatic decline in fox numbers had a profound influence on the movement and behaviour of the survivors. Indeed, in their 2001 book Urban Foxes, Stephen Harris and Phil Baker point out that:
“…with all these changes, therefore, it is simply impossible to estimate just how many urban foxes there are.”
There have been reports in the newsmedia, following the recent case of a fox biting nine-month-old twins Lola and Isabella Koupparis in Hackney (London) on 5th June 2010, giving the number of urban foxes as 34,000 animals, with almost half within the M25, but it is unclear from where these figures arose. The most recent attempt to gauge fox numbers in urban Britain was a viewer survey conducted as part of the Channel 4 mini-series, Foxes Live, broadcast in May 2012. The data from the 11,000 responses have yet to be fully 'crunched' by the biologists involved in the study (Dawn Scott at Brighton University and Phil Baker at Reading University), but the preliminary analysis suggested there are between 35,000 and 45,000 foxes living in urban Britain. The population has, it seems, probably risen in step with increasing human populations. Dr Scott informs me that they are planning to publish a more detailed analysis of the survey data later in 2012.
A question of time
So, in conclusion, without regular census data it is impossible to say precisely what is happening to Britain’s Red fox population. Nonetheless, the data we do have suggests that rural populations are either stable or slowly declining (and have been for almost a decade), while urban populations are probably increasing as a response to recovery from mange – it is, nonetheless, impossible to estimate urban numbers or trends with any accuracy while the population is in such a state of flux. (Back to Menu)
Q: Is it likely that a fox will attack me, my child, my cat or my dog?
A: The short answer is: No. It is, as we shall see, certainly not unknown for foxes to attack cats and, more rarely dogs and people, but none of these incidents are likely. I must say from the start that I understand and appreciate that this is a sensitive subject and that all the statistics in the world offer no consolation to someone who has lost a beloved family pet or who has been injured, or whose children have been injured, by a fox. I feel, however, that it is important to understand that the fact such events do happen, does not mean that they are common occurrences. That which follows is a summary of the information currently available regarding the occurrence of fox attacks on people, cats and dogs.
Lately, following the case of two young twins who were bitten by a fox in London, the UK has seen something of a media ‘frenzy’ over urban foxes and the danger they pose to people and their pets. The apparently unprovoked attack has left experts confounded and many people afraid of the animals with which they share their streets and gardens. Some newspapers have been quoting local pest control companies who say urban fox numbers are on the rise and they’re seeing more problems than ever before. Despite this, however, we do not currently know what is happening to urban fox numbers, although it is almost certain that they haven’t recovered from the outbreak of mange that decimated populations in the mid-1990s. Fox numbers probably are increasing as a response to this recovery but there is no way to confirm this without recent census data (see QA) – it is worth remembering that, unless you can conclusively identify each individual, seeing more foxes doesn’t necessarily mean there are more foxes about. Similarly, there is currently no evidence that foxes are more of a nuisance or more dangerous now than at any point in the last decade.
When it comes to assessing the evidence, whether it be scientific or otherwise, we must be mindful that we can only observe a fox for a fraction of its time (often using radio-tracking, which only tells us about the animal’s movements and generally nothing about what it’s doing at the time) and over a fraction of its range. Moreover, each fox is an individual: some are bold, some shy, some reclusive, some tenacious. We must thus be careful when generalizing; applying what we observe in one population, or even individual, to all populations may over- or underestimate the risk. Naturalist and writer Brian Vezey-Fitzgerald summed it up nicely in his 1942 book A Country Chronicle, in which he wrote:
“Dogmatism in any branch of natural history is not only foolish, it is a sin.”
I am keen to emphasise that this is not a case of ‘special pleading’ on behalf of the fox, and I am not suggesting that foxes are blameless. I am simply keen that our opinions and actions are based on a rational and balanced appraisal of all the evidence.
Fox attacks on People
Concerns about urban foxes were probably first voiced by the media in an article about ‘vulpicide’ in the London town of Orpington that appeared in The Sunday Times on 17th June 1973. The article told how Bromley Council -- the borough in which Orpington sits -- had employed a full-time fox-control officer who was responsible for shooting and gassing foxes in the area; apparently, this was in response to a small child having been attacked by a fox. It seems, according to this article, that the ‘attack’ actually took the form of a young boy who said a fox jumped at him in an outside toilet at the Battle of Britain airshow. The article contained excerpts from Bromley Council minutes warning of the threat that urban foxes posed to people and their pets. Similar articles crop up from time-to-time and many carry a quote from a source who says ‘it is only a matter of time before someone is seriously injured by an urban fox’. Unfortunately, despite their unequivocal rarity (especially considering the estimated number of foxes and their proximity to people in towns and cities), several incidents have been recorded, although the validity of some accounts has been questioned.
The next case of which I am aware made the press -- in The Independent -- just over two decades after the original Sunday Times article. In early November 1996, five-month-old Philip Sheppard needed hospital treatment for an injury to his face after apparently being bitten or scratched by a fox while lying in a pram in his parents’ conservatory in south London. According to the media report, his mother came out to investigate his cries and found the fox on top of him. The paper quoted various fox experts, all of whom were astounded by the attack and some who questioned the culprit, suggesting that the wounds were more reminiscent of having been scratched by a cat. In response to this story, Bristol University ecologist Stephen Harris wrote a short article to Country Life magazine later that month in which he described the hysteria that followed the attack as a “misinformed overreaction”. Professor Harris explained:
“The fox did not attack the baby and made no attempt to bite it; at worse, it was slightly too inquisitive.”
The title of Professor Harris’ article, “Foxes pose no threat in cities”, summed up his opinion (and remains the opinion of many fox biologists) on the matter.
In late June 2002 there was a report of a fox biting a 14-month-old boy who was asleep in the lounge of a house in Dartford, Kent and, on 9th September 2003, The Sun carried the story of four-year-old Jessica Brown who was, according to the paper (and, it has to be said, in true tabloid style), “mauled by a starving fox” while lying in her bed – the accompanying photo showed a u-shaped bite and localised bruising on her left arm. Following several reports of foxes apparently taking pets in Edinburgh, an article appeared in The Scotsman newspaper when a local pensioner was bitten. In August 2004, Margaret O’Shaughnessy was bitten on her left ankle by a fox while putting out milk for her cat in her garden in the Firrhill area of the city. Additionally, January 2007 saw the case of two paperboys who found a two-year-old baby boy crawling down a street in Croydon, South London at 6 am being followed by a fox. According to an article in The Sun, the boys had to “kick away a snarling fox before picking up the tot”. I should mention that there is nothing in the article to suggest that the fox actually harmed the baby and one is tempted to think the animal was following the baby out of curiosity.
The incident that most will be familiar with is the widely publicised case of two young girls who were bitten by a fox in a London suburb earlier this year. In a terraced house in Hackney, Greater London, just before 10pm on 5th June 2010, Pauline Koupparis went upstairs to investigate the crying of her nine-month-old twins -- Lola and Isabella -- and found them in their cots bleeding from deep wounds to their upper body inflicted by a fox that was still in the room. Mrs Koupparis called for her husband and together they tried to remove the ‘medium-sized’ fox, which was apparently unfazed by their lunges; eventually they managed to chase the animal downstairs and out into the garden. The children were rushed to the Royal London Children’s Hospital, where they were treated for severe soft tissue injuries. Isabella suffered a severe bite to her left arm, while Lola sustained a minor bite to her right arm and a serious bite just above her right eye. This story attracted much media attention and was broadcast around the world; various fox experts expressed their surprise at the incident and some questioned whether it was actually a pet cat or dog that was to blame. In the documentary on the incident broadcast by the BBC, the Koupparis family re-iterated that it was most definitely a fox and explained that they do not have any pets. Despite some rather disturbing and, at times frankly appalling, abuse the family received from certain members of the public, the police investigated thoroughly and, based on the wounds and expert testimony, were satisfied that the twins were bitten by a fox. This attack raised many questions about urban foxes -- about whether they were getting bolder, more numerous, or hungrier, in short, whether they are more dangerous now -- and caused much speculation as to the reason behind the animal’s behaviour, including that it might have been a cub or a mentally unwell fox.
This case is quite remarkable because, not only did the fox enter the house (that can perhaps be explained by the remains of a barbeque left cooling in the kitchen), but it also went upstairs and seemed quite ‘at home’ – it has been suggested, incidentally, that the fox may have been attracted upstairs by the smell of the nappies and such items are occasionally found at earths. Why it bit Isabella and Lola we will never know, but some have implied that it shouldn’t be a surprise given that ‘a young baby isn’t much bigger than a lamb or piglet’. I do not wish to detract from the fact that this was a serious incident and terrifying for all those involved and so I don’t want to discuss this more than to make the point that, even where such prey are available, cases of foxes taking lambs and piglets are uncommon and the bulk of a fox’s diet is composed of much smaller prey, namely invertebrates (especially earthworms), rodents, birds and rabbits.
Why the fox wandered around the house might be alluded to by Mr Koupparis’ comment in the documentary that the fox “sat at the top of the stairs like a family pet”. I have seen many videos showing foxes being enticed into houses by people offering food and readers have sent me photos of foxes lying by their fireplace or standing in their kitchen waiting for food. I have equally seen people strike up that ‘special relationship’ in which the fox feels secure enough to take food from their hand and people who have awoken to find a fox asleep on their bed. It seems that some people see urban foxes as a ‘free pet’, forgetting that they are actually wild predators.
I personally do not see a problem feeding foxes, on the provisos that only a small amount of food is put down (e.g. a handful of dog biscuits scattered on the ground will divert the animal’s attention for long enough to get a decent view, and probably a couple of photos) and that the foxes do not become accustomed to the food or the person providing it. I would recommend putting food down only a couple of nights per week (the foxes will still come, just in case, but won’t come to expect food) and do not stand or sit in the garden while the foxes are there – find a comfortable seat at a window and watch from inside. Never encourage a wild animal to take food from your hand and never entice them into your house. Foxes are opportunists and, in the case of the Koupparis attack, it seems possible that if someone in the neighbourhood had encouraged the fox into their house for food, the animal wouldn’t turn down the opportunity for an easy meal in a nearby house that might perhaps have a similar layout – foxes have a very keen sense of smell and can readily distinguish regular human ‘watchers’ from newcomers, so I think it unlikely that the animal would have mistaken the houses. This is, of course, only a theory, and one that can never really be proven.
Shortly after the Koupparis twins were attacked, thirteen-year-old Bethany Blackburn was bitten on her left foot by a fox that, according to media reports, tore a hole in the tent in which she was camping with two friends just before midnight on Sunday 25th July. According to one report, the fox spent two hours scratching at the side of the tent, before it got in. An article in The Daily Mail told how the fox "sat, snarling, in the porch area, only turning tail when Bethany's mother, who the desperate schoolgirl had alerted on her mobile phone, switched on the kitchen light and came out to investigate". This incident happened in the Blackburn’s back garden in a suburban part of Long Ditton, Surrey. Miss Blackburn told the paper that the fox, which the girls said was a cub, returned to the garden the next night and urinated on the tent door. There was apparently no food around at the time and it remains unclear what attracted the fox to the tent, but snarling is most certainly an abnormal behaviour. The marking behaviour is not unusual, however; foxes very often scent-mark novel objects in their territory, and a tent would certainly fit the bill. Since these incidents a couple more have made the press. In September 2010 Annie Bradwell was bitten on the ear by a fox while in bed in her house in Fulham, West London and in the early hours of Sunday 24th October 2010, a 37-year-old man was found unconscious by police in St Michael's Parish Church Cemetery in Musselburgh, East Lothian (southeast Scotland) suffering from hand and facial injuries, which are thought to have been caused by an animal. There is no direct evidence linking the injuries to a fox, but a local councillor was quoted by the BBC as saying: "I stay not far from that area and the only animals around capable of doing such a thing are foxes." In January 2011, Tammy Page was bitten on her left index finger while trying to expel a fox from her kitchen and, later in the same month, Deborah Adams was bitten on her left arm when she tried to touch a fox she found sitting in the road leading to Gluvian Farm in Cornwall.
Of course, these are the cases that have made the press, and one wonders how many go un-reported. I, for example, know of at least one attack -- during August 2005 -- in which a gentleman in south-east England was apparently charged by a fox that “ran the length of the garden squealing” and bit his leg; so engrossed in this activity was the fox that it ignored being kicked by the man and blasted with a hose by his wife and only fled after the couple’s huskies were let out. This incident was recounted on an Internet discussion board but, although the gentleman spoke to his local Council about the incident, it doesn’t appear that any formal record was made of the attack and there is the suggestion that such incidents may be more common than we assume. Indeed, according to a pest control officer interviewed on the recent (2010) The Fox Attack Twins BBC documentary about the Koupparis attack, cases of foxes biting people are now common, but many people don’t report them, presumably for fear of suffering abuse similar to that levied on the Koupparis family. This situation is no doubt exacerbated because Britain, unlike most states in the USA, does not have a statutory body to whom bites can be reported and that keep track of cases. The Health Protection Agency’s (HPA) Zoonoses Department recommend reporting any bites/attacks to your Local Authority’s Pest Control Department, even though they will probably be unable to provide assistance in the removal of the fox. The HPA also advise anyone bitten by an animal (wild or domestic) to seek medical attention as soon as possible. It seems reasonable to assume that some bites will go un-reported, but ultimately this hampers our ability to assess the risks posed by foxes.
So, given the foregoing, can foxes be dangerous? The answer is yes. Do foxes pose a significant threat to people? The answer is no. Foxes probably are bolder now than they were when they first colonised our towns and cities back in the 1930s and 1940s, but I feel -- in the interest of calm -- that it is important to recognise that boldness is not synonymic with viciousness. Certainly, foxes are wild predators with teeth and claws that can inflict injury and bites happen from time to time, but such incidents are still extremely rare – I will spare you the statistical comparisons with dog and cat bites, because I don’t feel they are particularly relevant. It is important to be as cautious and sensible around foxes as you would any wild animal. Take common sense precautions and do not approach, or let your children approach, foxes that come into your garden. If you wish to take steps to exclude foxes from your property or deter fouling in your garden, there is advice on the Fox Deterrence page of this site.
Foxes and Domestic
In a paper to the Journal of Applied Ecology during 1981, Stephen Harris estimated the number of foxes in Bristol city and assessed some of the factors affecting their distribution. Harris collated 4,894 records of stray dogs (3,012) and cats (1,882) from Bristol Dogs Home, mapped them against records of fox presence and found that the concentration of stray dogs (but not cats) explained fox distribution in parts of the city. Harris wrote:
“This study suggests that a major factor affecting the distribution of foxes in Bristol is the presence, in certain areas, of large numbers of stray dogs.”
Indeed, Professor Harris found that stray dogs commonly disturbed and chased foxes. Moreover, during the study 87 dead cubs were recovered from the city, 13 (15%) of these were found to have been killed by animals and, in most cases, dogs were responsible. If we consider that most foxes are about the size of a large domestic cat, they probably pose a potential threat to only the smallest breeds. There is, however, some evidence that foxes are perturbed by the presence of dogs and there have been reports of foxes ‘intimidating’ people out walking their dogs; these accounts are often dismissed by researchers, but I have received several accounts of such instances. These cases include a lady who was followed by a fox while out walking her dog after dark, until she crossed a road (presumably a boundary of the territory) at which point the fox turned and left. Another example was that of a lady in London who was repeatedly barked at and followed by a fox while out walking her Belgian Shepherd dog at about 11pm in June (2010). In these cases, and a couple of others readers have contacted me about, the dog appears the focus of the fox’s attention and it seems probable that the fox was anxious at the dogs’ presence.
Not all fox-dog encounters are irascible and I have come across accounts of dogs playing with foxes. In May 2007, the BBC Wildlife Magazine published a supplemental booklet called Fox UK, which contained information about foxes (compiled by Professor Harris) along with photos and stories sent in by readers. In one letter, Mike Squires of Wales told how his 15-year-old Border Collie spent several minutes playing with a fox in their garden one December morning, with each taking it in turns to chase the other. In his 1986 book, A Fox’s Tale, Robin Page tells how a fox cub he raised would play with the farm kittens and their black Labrador. Similarly, in February 2007, a lady wrote to me describing how a fox followed her while out walking her Welsh Terrier in Surrey and, when she stopped, it approached and started play bowing to her dog. In Town Fox, Country Fox Brian Vezey-Fitzgerald also recounts examples of foxes playing with dogs in his neighbours’ gardens -- in one case a Dachshund and in the other a Miniature Poodle -- although, he points out that in his experience foxes generally avoid dogs:
“The fox avoids dogs rather than ignores them. I do not think there is any question of fear involved. Certainly I have seen no sign of fear. And I think that the fox is not an easily frightened animal. Avoidance is merely an elementary precaution.”
Foxes and Domestic Cats
In February 2005, the Daily Telegraph carried the headline “Hungry foxes start eating the nation’s cats” and, in the accompanying article, told how fox attacks on cats were on the increase and quoted a pest controller near Edinburgh who explained that the fox population has gotten out of hand because the introduction of wheelie bins has deprived foxes of their regular food supply. As we have discussed already, there is no evidence of this, so if the number of fox attacks on cats has increased (or is increasing) it seems the reason lies elsewhere.
There are few data sets to tell us how many cats are attacked by foxes each year and there have been no recent attempts to collate records. Probably the most off-cited statistics on the subject come from Bristol University. Professor Harris surveyed an area of north-west Bristol by distributing 5,480 questionnaires asking about fox disturbance, including losses of pets – 5,191 (95%) surveys were returned and, from these, it was estimated that there were 1,225 pet cats in the area. From the data, Harris calculated that eight (less than 1%) of these pet cats, most being kittens less than eight months old, were thought to have been killed by foxes.
The problem with the Bristol data is that it is not recent; it first appeared in a paper by Harris on the food of suburban foxes published in the journal Mammal Review during 1981 and the questionnaire was actually circulated in October 1977. When we consider that, in a 1986 paper to the Journal of Animal Ecology about urban foxes in Britain, Harris and Jeremy Rayner note that the “colonization of London by foxes is continuing” and that subsequent studies in Bristol showed how the urban fox population peaked during the early 1990s, it is unclear how relevant these fox-cat statistics are today, 35 years on. A similar, questionnaire-based, study in Oxford conducted by David Macdonald at the city’s university during the early 1980s yielded similar results to the Bristol survey – in this case, nine (again, less than 1%) of the 6,143 respondents believed their cat had been killed by a fox.
Dietary studies and observations of cat bodies at fox earths suggest the numbers may be higher than the surveys imply. Most rural studies don’t make mention of cat remains in either fox scats or stomach contents, but during his 1981 review, Harris found cat remains in 2.1% of stomachs he studied, while a similar study on the food ecology of foxes in Sweden, conducted by Jan Englund during 1965, found cat remains in just under 2% of stomachs. Macdonald’s studies found lower levels, with cat fur in eight (0.4%) of the 1,939 scats they collected. The problem, of course, with making inferences based on remains is that the foxes could’ve scavenged the remains – in November 2006, the insurer Petplan estimated that some 230,000 cats were run over in Britain every year (an average of 680 per day), with Bristol topping the blackspot list. Given that foxes are well known to scavenge roadkill, it seems this habit may equally well explain the presence of cat remains in their diet.
There can be no argument that foxes are capable of killing cats and, in some instances, they do; such incidents, however, are not common and are not considered a significant source of domestic cat mortality. In his entertaining and well-written account of urban foxes, published in the October 1985 issue of the BBC Wildlife Magazine, David Macdonald pointed out:
“… both species are numerous in towns and active nightly in the same gardens, where they meet continually. If foxes in general were a serious threat to cats the losses would be huge.”
Macdonald went on to describe how stalking with infrared binoculars in Oxford allowed them to watch fox-cat interactions on many occasions; most cases involved the two ignoring each other, but where conflict was seen the fox was apparently the more nervous of the two. A similar position was taken by Stephen Harris and Phil Baker in their 2001 book, Urban Foxes, in which they noted how foxes must meet many cats on their nightly forays and, in the Fox UK booklet, Harris wrote:
“As for cats – well, I have witnessed many encounters between foxes and cats. The cats win every time, since the foxes are reluctant to risk injury when faced with such a powerful foe.”
Both species are, indeed, numerous with an estimated fox population of some 250,000 animals. In 2010, the Pet Food Manufacturer’s Association estimated there to be around eight million domestic cats in Britain, which would be roughly one fox per 40 cats.
Probably the biggest hurdle to assessing the number of cats killed by foxes is that both species are nocturnal, which means that encounters are rarely observed and the first the owner knows of the confrontation is when they find the body the following morning. This leads to a certain amount of conjecture, not least because it can be very difficult -- if not impossible -- to separate the wounds made by a fox from those made by dog. It is often assumed that a fox is responsible because one (or several) has been seen in the area and no dogs have ever been seen in the garden, although the Dogs Trust’s 2009 Stray Dog Survey found that just over 107,000 stray or abandoned dogs were picked up by Local Authorities across Britain in 2008. There have been several incidents, where a fox was believed to have killed a cat, that have made the local and national press in recent months and most follow the same line: residents are woken by what they describe as a cat fight and, in some cases, a fox is seen at some point during the night. Recently, I came across the case of a veterinary nurse from Manchester, who regularly has foxes feeding in her garden, which emphasizes the difficulty in being sure (parts of her original note are reproduced here with her permission):
"At 8.00 this morning [23rd January 2011], we let our cat out (he is a lazy, diabetic cat, with no interest in birds or other wildlife. He lives for his meal times and does not venture out of our garden, so does not leave his business in other gardens). I went upstairs and at 8.30 my daughter came up screaming that he was being attacked by 2 dogs in our garden. We ran downstairs to find 2 terrier type dogs - one had him by the throat, the other by the back legs. When I ran out, they tried to carry him off, but I managed to get him. I am lucky that I was able to assess his condition until I could take him to the vets where I work (we are not open on Sunday, so I had to get the vet up, for which I am eternally grateful). He is now on a drip, with IV antibiotics and pain relief. He has been lucky - in the respect that I was able to take him away from the dogs before they tore him apart - which they would quite literally have done. One of his hind legs is very badly injured, and will be x-rayed tomorrow. It looks badly broken, and to be honest I expect the eventual outcome will be amputation. He is also concussed, he was thrown to the ground with such force. To get back to the point - if we hadn't caught the dogs in the act, we would have found pieces of our cat strewn around the garden and assumed that the 2 foxes we watched in our garden the other night were responsible."
Ultimately, it is very rare for the fight to be observed, although there are some notable exceptions. In late August 2003 there was an incident in which six foxes were seen attacking a 12-year-old tortoiseshell cat in a back garden in Corstorphine, Edinburgh. One of the cat’s owners managed to scare the foxes away and rushed it to the vet, but unfortunately its wounds were too severe and it had to be euthanized. This case is unique because it involved several foxes. Foxes are solitary hunters and do not hunt in packs; the parents do, however, teach their cubs how to hunt and cubs may accompany them on hunting trips – this is presumably what was happening here as, by this time, the cubs would be almost fully grown and almost indistinguishable from the adults. Another incident happened much more recently, in August 2010, and involved a fox entering a house in Folkstone, Kent through an upstairs window and attacking an eight-week-old kitten. As with the 2003 incident, the owner intervened and caused the fox to drop the cat and flee, but the kitten had to be euthanized several days later. This is the first case of a fox entering a house and attacking a cat, raising the question of whether someone locally had been feeding it in their house prior to this. The final example I plan to include is one e-mailed to me by a lady in Hampshire who, in the early hours of the morning of 23rd January 2011, witnessed a fox dragging a cat outside their house (part of her e-mail is reproduced here, with her permission):
"At about 3.30 in the morning I was awaken by a kind of strangled cat wail. I live in a surburban area with flats opposite and we often have cats fights so running to the window (we have a very large cat who often fights!) we were very shocked to see a medium size fox dragging a struggling cat by the scruff of the neck infront of the flats - about 15 metres, stopping to readjust and then across the road towards our house. At that point (another 10 metres) my friend made a loud hissing noise not knowing what else to do and this startled the fox which dropped the cat. The cat immediately ran very fast away while the fox looked up an then started walking past our house (opposite direction from where it had been running with the cat), looking at the house then glancing back towards where the cat had run. The fox was just walking slowly and calmly away. It was not our cat, but it was a medium size cat, not small or 'kitten looking' and it ran fast away very fast."
If we see a fox attack a cat, that’s one thing, but how can we be sure that the cat was killed by a fox if we didn’t witness the incident? Well, there are some features that tend to be associated with (although are not conclusive proof of) fox attacks, rather than dog attacks or fights with other cats. It has been suggested that intercanine distance (i.e. the size of the gap between the canine teeth) can be used to identify the culprit, but foxes and medium-sized dogs both have distances of around 30mm and 26mm (about one inch) for their upper and lower canines, respectively. Indeed, in a paper to the journal Wildlife Research during 1970, Ian Rowley presented the results of his five-year study on lambing flock mortality in south-east Australia and wrote of:
“… the impossibility of differentiating between fox and dog attack on the basis of the wound inflicted …”
Nonetheless, decapitation and the smell of fox on the body are both strongly associated with cats killed by foxes. In his Town Fox, Country Fox book Brian Vezey-Fitzgerald described two instances where one of his cats appeared to have been in a fight with a fox and, in the first instance, he noted how the cat smelt strongly of fox; several readers have contacted me saying much the same.
So, we know that foxes do sometimes attack cats, although we cannot say how common such encounters are. This raises the question of why? Why attack something that's about the same size as you, with sharp claws and teeth? Potential food may be part of the equation and, as has been suggested for foxes predating hedgehogs, it has been implied that some foxes may be more likely to attack a cat than others – this might explain local ‘blips’, where several cases are reported in the same town in a short period. I have heard it argued that the 2003 incident actually represented a case of parents showing their cubs how to hunt cats and, while I feel this is an unsubstantiated conclusion, it cannot be disproven. The most likely explanation, in my opinion, is that foxes see cats -- and, for that matter, cats see foxes -- as both competition for food and possibly a danger to their young (there are reports of cats killing fox cubs). It is not difficult to see how two equally-sized carnivorans setting up territories in the same areas and hunting for the same food could lead to conflict. Consequently, such attacks represent what biologists refer to as competitive displacement – one animal kills another to remove competition for a resource. Indeed, this idea appears to gain more weight when we consider reports from some farmers suggesting that rural foxes are often very hostile towards farm cats. In the same e-mail describing the fox dragging the cat, the reader told me:
"My grandfather, who was a farmer in Sussex, often berated fox lovers, citing an instance of his farm cats being dragged screaming down the road by a fox which killed it despite being chased - in daylight."
We obviously cannot draw any firm conclusions on the above without knowing all the facts but, if foxes do view cats as potential competitors, this competition would conceivably be greater in rural locations; here foxes feed more heavily on rodents, birds and rabbits, all of which are also on a cat's menu, whether additional food is provided for them or not.
Ultimately, I feel that the outcome of any given fox-cat encounter will depend upon the two individuals involved and the relationship is far from straightforward. I have seen many videos and heard many stories of cats (even kittens) chasing off foxes; I have read accounts of foxes chasing cats; I have heard stories (some from my readers) of cats and foxes playing together and I have even come across an account of the two species apparently hunting voles together. So, if you’re concerned about the risk foxes pose to your cat, what can you do? There are steps you can take to exclude foxes from your garden, but it is unlikely that your cat restricts its nightly wanderings to your garden alone. Given that both species are nocturnal, and that there is no guaranteed method of controlling the movement of either species, the most effective way to protect your cat is to keep it in at night, thereby vastly reducing the likelihood that it will come into contact with a fox. This is also likely to reduce the probability that it will fight with any other cats, or dogs, and should reduce its impact on the local wildlife population. Additionally, keeping your cat(s) in at night also reduces the likelihood of it being involved in traffic accidents at times when there are few people around to see/help and veterinary assistance is more difficult to find.
So, in conclusion it cannot be denied that foxes do attack cats, dogs and even bite people on occasion. None of these events, however, is commonplace and -- while I appreciate that people who have lost their cat or dog to a fox, or been bitten by one will probably disagree -- I do not believe that the current evidence supports the suggestion that foxes pose a significant risk to people, their cats or their dogs. I feel there is a considerable need for more research on the subject of fox-cat and fox-human interactions in order to quantify the risk. I feel as our cities continue to expand, the conflict between humans and wildlife is inevitably going to increase. Eradication of foxes from urban settings is impractical and, for many people, unacceptable, so a change of attitude is required. Elsewhere in the world, people share their towns and cities with much larger carnivores than we have here in Britain, but a common sense attitude prevails and problems are surprisingly rare. (Back to Menu)
Q: Should we be culling urban foxes?
Short Answer: Introducing a culling programme would really only be a means of restoring public confidence. The public are understandably unnerved when stories make the news about foxes biting people (especially young children) and local councils refusing to take action. The problem with culling, however, is that it must be done properly and, in order to have a long-term impact, it must be sustained. It is generally accepted that in the region of 70% of the population must be killed before a decline is likely and the cost and manpower of achieving this in urban areas makes control very expensive. The logistics of culling foxes in urban areas (especially on city streets) makes control very difficult. Culling of rural animals is well-known to depress population numbers, but evidence from urban areas suggests the impact is less evident (owing largely to higher population densities). There is an argument for implementing an urban control programme as a means of restoring public faith, but it seems unlikely that the costs associated with such a scheme, coupled with the futility of its goal (i.e. to reduce fox numbers) means it is unlikely ever to be seen as a viable option for funding, especially when the country is in such a financially fragile state and local councils are having their budgets reduced. Ultimately, deterrence and the widespread application of common sense (namely clearing up dropped food and recognising that foxes are wild animals, not pets) are better options for reducing fox disturbance.
The Details: The urban fox is an animal capable of polarizing opinion like few others and lately there has been something of a furore following several reports in the press of people being bitten by foxes that had entered their homes uninvited. In the press we have seen cries for local councils to do something about the ‘huge explosion in the fox population’, and statements about how urban foxes are bolder and causing more problems than ever before. There can be little doubt that some foxes are bolder than many of us would perhaps like; this is a natural behavioural response to living side-by-side with a species (i.e. humans) that not only poses little real danger, but -- in many cases -- actively encourages close contact by providing food. The fact, however, that an animal is bold, does not automatically mean that it is dangerous. Many years ago, where I used to live in West Sussex, we had a starling (Sturnus vulgaris) that would come into the house, sit on the sideboard and watch us – this was invariably the boldest starling I have ever known, but at no point did it pose any threat. I appreciate, of course, that foxes are wild predators capable of inflicting more damage than a starling, but my point is that just because an animal doesn’t immediately flee from you does not mean it instinctively poses a threat. Despite the very unfortunate -- and still very rare -- cases in recent months, foxes and humans pass close by one another hundreds of times every week (whether each party knows it or not) and neither is a danger to the other.
I have addressed, elsewhere on this site, the questions of whether the fox population is currently increasing and whether foxes pose a significant threat to people, so I shall not discuss them here. I would like, however, to reiterate the point that, although fox populations might be increasing, there is no evidence of an explosion in numbers in recent years. I appreciate, of course, that it is only natural for people who start seeing foxes more often than normal to equate this with there being more foxes around; in order to be certain, however, you must be able to positively identify every individual. There are other factors that may account for simply seeing foxes more often, including that they are becoming more diurnal (i.e. spending more of the daytime active) or are using this part of their territory more than they used to. Nonetheless, whether the increase is real or perceived, stories of fox attacks in the media -- and the unfortunate hyperbole, in some cases arguable propaganda, that seems a mandatory accompaniment to many news articles -- make people understandably nervous. The problem is exacerbated when people contact their local council expecting them to send someone to ‘take care’ of the problem, only to be told that foxes aren’t considered vermin (in the technical sense, this list is compiled by DEFRA) and councils aren’t obliged to take any action.
I have read many articles recently in which people have said foxes need to be controlled because their numbers are growing out of control and they have no predators. It is certainly true that there are none of the large Carnivora in the UK (although it is arguable how much of an impact predators have on fox numbers), but this doesn’t mean that fox numbers aren’t subject to control.
The nature of control
Disease can also be a limiting factor and this has been well documented in Bristol’s foxes. Disease is what biologists refer to as a density-dependent factor – its impact increases as numbers rise, because more individuals in an area means more contact, which helps the spread of parasites and viruses (think how quickly a cold virus spreads around the office). In a 2001 paper to British Wildlife, Phil Baker, Tabetha Newman and Stephen Harris described the changes they observed when sarcoptic mange arrived in Bristol. Sarcoptic mange is a skin infection caused by a parasitic mite and is extremely virulent in foxes; without treatment, it typically proves fatal within four-to-six months. Between 1990 and 1994 the fox population in their study area -- in the north-west of the city -- increased almost five-fold, largely in response to a super-abundance of food provided by householders. Things changed in May 1994, when a juvenile male heavily infected with mange returned to the study area having spent the winter outside the city. The disease spread rapidly through the foxes on the study site and the population crashed – by the spring of 1996, the study population had been wiped out and Baker and his co-workers found the situation to be similar across the city, with an estimated 95% of Bristol’s foxes having died. By 2004, fox density was about 70% that of the 1990, and only 15% that of the 1994 (record density), population. Mange is still prevalent in many urban areas (although seemingly less so in rural foxes) and is considered by many to be limiting the growth of infected populations.
Predation can, in some circumstances, limit populations; generally-speaking the greater the predation pressure, the more difficult it will be for a population to become established or grow. We have already mentioned that foxes have no major predators in Britain (although badgers and eagles have been known to kill them), but Stephen Harris, in a 1981 paper to the Journal of Animal Ecology, reported that stray dogs were a significant factor explaining the distribution and mortality of urban foxes in parts of Bristol. Indeed, Harris found that stray dogs commonly disturbed and chased foxes; during the study, 87 dead cubs were recovered from the city, 13 (15%) of which were found to have been killed by animals and, in most cases, dogs were responsible. Car accidents, although not a direct surrogate for predation (because they’re unselective), claim many fox lives each year – there are no specific studies of which I am aware, but best-guess estimates (as published by the Burns Enquiry) suggest some 100,000 are killed annually on Britain’s road network. If you’re wondering, incidentally, why you rarely see road-killed foxes in towns, it’s because most councils have an ‘open spaces’ team that are responsible for removing the carcasses.
There is one final, perhaps less obvious, limiting factor that affects fox populations: space. Foxes are highly territorial mammals and, although they require smaller territories in urban areas than in more rural settings (meaning densities, or foxes per given area, can be higher in towns and cities), they still maintain territories from which they will exclude others. Consequently, there is only a limited number of fox families that can exist within a given area and, as numbers increase, every available space becomes occupied and it becomes more difficult for foxes to move in from the surrounding area; finding a territory near their parents is also difficult, making dispersal more likely. A crude analogy would be a hotel; as rooms are booked the amount of space left for others diminishes until the ‘no vacancies’ sign goes up. The territorial nature of foxes is a crucial concept to understand and will become important as we come to look at the effectiveness of control schemes. Each territory will contain a mosaic of different habitats (gardens, parks, industrial estates, cemeteries etc.), allowing the fox to obtain all necessary resources; one such resource is a little peace and quiet. It may sound bizarre, but in a series of papers (during the mid-1980s) looking at the spread of urban foxes in the UK, Bristol University biologists Stephen Harris and Jeremy Rayner found that foxes were more common in areas of medium-density housing, as this provided quiet gardens in which they could rest during the daytime. The biologists concluded that a lack of such resting sites probably explained why foxes were relatively scarce in, and slower to colonize into the heart of, large cities or heavily industrialised areas.
The aforementioned data were, of course, collected more than three decades ago and nobody is suggesting that foxes never inhabit highly disturbed areas (it’s clear that they can tolerate very high levels of disturbance). It is, nonetheless, noticeable that even foxes living in the heart of our major cities tend to be found resting in less disturbed gardens and areas of parkland during the daytime and some experts still consider the level of disturbance to be a key limiting factor. Indeed, as recently as 2010, in their review of urban foxes published in the Urban Carnivores compendium, the Bristol biologists wrote:
“The planned future construction of large numbers of high-density housing units with small gardens in Britain is, therefore, likely to be unfavourable for foxes.”
Disturbance need not always come from humans in order for it to be a crucial component in fox population regulation. Indeed, social factors in general can play a significant role in setting the upper limit for a fox population. During his experiments on the Red fox population in Sweden during the 1960s, Jan Englund was the first to suggest that different populations may be controlled by different factors - i.e. foxes in some areas might be limited by social factors, while those in another part are controlled by the level of available food. In a paper to Holarctic Ecology during 1989, Grimso Wildlife Research Station biologist Erik Lindstrom put this theory to the test on fox populations in south-central Sweden. Lindstrom found that this fox population was directly limited by food supply in years when vole numbers were low and were socially regulated when vole numbers were moderate or high. So, when food was scarce, it was this lack of food that controlled fox numbers, but as prey increased in abundance and food was no longer limited, the upper limit of the fox population fell under the control of social factors. This highlights that fox populations do not continue to grow inexorably, even when food is plentiful.
Lindstrom's data are not unexpected and it is not uncommon for limiting factors to operate in an almost linear succession; in other words, for one to take over from another as conditions change. If food were the limiting factor, for example, and we increase the rations -- let’s say people put out food to help the starving animals -- the population can start to increase again, now the limitation of food has gone (or more accurately, been raised). The population will increase until something limits it once more; until there is insufficient water, or a lack of suitable shelter/resting sites, or food is limited again, or disease starts spreading, et cetera. This ‘tussle’ for resources is known as competition and when animals of the same species are going after the same resource, we call it intraspecific competition.
So, are foxes over-abundant in cities? Well, there are no reports of large-scale die-offs among urban foxes resulting from starvation, suggesting that foxes are not ecologically over-abundant. The fact, however that Britain’s urban fox populations are under biological control -- predominantly disease and space limitations -- and suffer relatively heavy losses on the roads doesn’t necessarily mean they are controlled to a socially acceptable level and this explains why there are still calls for fox control. The natural limitations on the population appear to permit higher numbers than many people will tolerate and it becomes necessary to try and quantify this ‘over-abundance’ in sociological terms – in other words, we have to answer the question: how many foxes is too many foxes? This is usually subjective and it is always difficult to calibrate nuisance; even if there was only a single fox family living in a town, if they live in your garden, kill your pet or, worse still, bite your child, it may be one family too many. The end result is that -- unless foxes are exterminated from cities (which is exceptionally unlikely) -- there is always the potential to see calls for additional control, simply because some people will tolerate more disturbance than others. This subjectivity was illustrated nicely in 1979, when Bromley council received a complaint from a resident about a family of foxes living in an over-grown allotment that backed onto his house. The council circulated a questionnaire to all 248 houses surrounding the allotment asking whether the foxes should be removed and, of the 76 people who replied, the vast majority (93%) voted against control, so the foxes were left alone. Still, when there is considerable public pressure to implement a cull, can such measures solve the problem? It seems logical, after all, that if you kill some foxes then there simply must be fewer animals around to cause problems? Unfortunately, it’s not quite that straightforward.
The effectiveness of urban fox control In January 2002, Bristol City Council produced an advisory booklet entitled Living with Urban Foxes, in which they summed up succinctly why they don’t operate a fox control service:
“Controlling urban foxes is difficult, expensive and never successful.”
This is a fairly accurate summary of the situation and several local authorities in Britain started and, for these reasons, stopped fox control schemes. Stephen Harris provided an authoritative and comprehensive review of the history of urban fox control in a paper, published in The Humane Control of Land Mammals and Birds (the Proceedings of a Symposium held at Surrey University during September 1984), so I won’t go into detail here. Suffice to say, the best efforts of MAFF (now DEFRA) -- which began in the late 1940s and included organised fox shoots in larger parks, allotments and waste ground, and destruction of breeding earths with terriers -- were unable to prevent foxes spreading into central London boroughs, or reduce the number of complaints received and, in 1970, MAFF relinquished this role. A few borough councils took over but, according to the 2010 review by the Bristol mammalogists, by 1980 only 15% of authorities in England and Wales undertook some form of fox control, and there are currently no councils in Britain that offer a fox removal service. This may, however, be under review – following the attack on the Koupparis twins in London, the Leader of the Commons, Sir George Young, said the Government would consider whether the law should be changed to force councils to control foxes.
Why have these control methods failed? The answer is relatively straightforward, as the Burns Enquiry put it: “fox populations are extremely resilient to culling”. There are two reproductive mechanisms that enable foxes to withstand very high levels of mortality and both revolve around the fact that culling temporarily reduces the number of animals in the population, thereby freeing up resources for those left behind. Firstly, the number of breeding vixens increases as culling intensifies. It has long been considered that dominant vixens suppress breeding of subordinates in the family group, although precisely how this is achieved is less obvious and probably involves several methods. Dominant females are well-known to kill the cubs of subordinate vixens (a phenomenon known as infanticide) and in 1994 a team of zoologists, based in Bristol and Scotland and fronted by Gill Hartley, suggested that the breeding of subordinate vixens was suppressed through a “social stress” mechanism. We know from studies on Bristol’s foxes that, in some urban populations at least, subordinates do mate and many conceive. Interestingly, unless there is a super-abundance of food or the dominant vixen is killed, these subordinates abort their litters very late term, which is thought to be a kind of ‘keep your cards hidden until the last minute’ strategy. A second mechanism is variation in litter size, which tends to be inversely proportional to population size – in other words, as density increases, the average litter size decreases. Ergo, culling initially reduces the number of foxes in the family group, reducing intraspecific competition for resources and meaning more vixens reach breeding condition and thus more cubs are born. Alternatively, the reduced competition may not result in more breeding vixens, but instead permit larger litters to be raised and more cubs to survive to maturity.
Culling can also influence the spatial dynamics of fox populations. The Bristol biologists estimate that about 15% of foxes are itinerant; they have no fixed home range and wander from place-to-place. Additionally, foxes may disperse at any time of the year and dispersal can be linked to both social and resource-based factors. So, as individuals are removed they leave space behind suitable for other foxes, which could be itinerants or dispersers looking for a territory, or it could be a neighbouring group who expand their territory to include this newly-vacant plot. If it helps, think of this situation as a ‘waiting list’ of dispersing and itinerant foxes looking for somewhere to settle down and raise a family. Studies by The Fox Project in conjunction with Andy Wilson (at the time a student of Greenwich University) have found that vacant territories in urban areas tend to have a new occupant within two weeks. The same studies suggest that lethal control can increase the number of itinerants in the population, leading to more complaints. Similarly, there has been the suggestion that several foxes may move in to contest a single vacancy, so you end up with more animals than you had before the cull! Studies of Bristol’s foxes during the mange epidemic showed that as families died out, neighbouring groups expanded their range to ‘take up the slack’. Conversely, tracking data collected from Oxford city by David Macdonald and Patrick Doncaster during the early 1990s showed that, when a territory became vacant, neighbouring groups might encroach on it, but they reduced their existing home range by an equivalent amount such that there was a constantly drifting ‘honeycomb’ of territories. Either way, immigration from outside the cull area is arguably a bigger factor explaining the temporary nature of fox control than is release from density-dependent factors such as breeding suppression or food shortage.
So, when we decide to cull a population we are faced with two significant compensatory mechanisms: more foxes being born, and the territories of killed foxes being rapidly taken over by a substantial source population. Can we get around this? The answer is yes, if we undertake a cull that is both initially deep (to achieve the reduction) and sustained (to maintain the population). If we consider that the average litter size in urban areas is four cubs per family group, it makes sense that even if you kill four foxes (i.e. 67% - this is where the oft-cited 70% figure comes from) you’re still left with two to start again next year. Moreover, as you start culling, the litter size is likely to increase, say to five cubs, and then you have to increase the effort to cull 71%, or 75% if the family has six cubs – and this is to keep the population stable. It is because, as we have seen in Bristol, urban fox populations have the potential to increase quickly when conditions allow that culling effort needs to be sustained if it is to have the desired effect of maintaining lower fox populations. It is, however, possible to implement local, seasonal control to reduce certain types of disturbance. Indeed, Game Conservancy Trust biologists Matthew Heydon and Jonathan Reynolds have shown that, in rural populations at least, this type of culling can have a significant ecological impact, reducing fox predation on game species.
By now you’re probably thinking: “but if fox populations are already stable then biological control and cars are already taking out 70%, so surely it shouldn’t take much input from us to tip the balance?”. The problem is that we don’t know what’s happening to the fox population; the most recent data (which is already four years old) suggest many stable populations, but increases in parts of the country and declines in others. Increasing, decreasing and stable populations will each respond differently to culling and with no way of knowing what's going on from region to region, we cannot track our progress and this in turn makes it difficult to assess cost-effectiveness. Given that no councils currently operate fox control programmes, there are no recent figures available pertaining to the costs incurred. A very brief vox pop of my local pest control companies suggested an average cost of between £100 and £150 (US$ 156 or €120) per fox, which seems fairly close to earlier figures quoted in the literature. In his 1984 review, for example, Stephen Harris noted how one local authority employed two men for three days per week throughout the year during 1983, resulting in 164 foxes being killed. The costs of salaries, overheads, petrol, ammunition and dog allowances totalled £11,000 (US$ 17,000 or €13,000), or almost £70 per fox. Of course, in terms of Government budgets, £11,000 is barely significant, but it remains to be seen whether such costs for what is likely to be an ineffective service can be justified when budgets are being reduced across the board.
In short, culling can be effective at reducing and suppressing fox numbers, but there are many factors to take into consideration and it is not a simple case of going out and shooting a few foxes to keep the population under control. The capacity of culling to reduce rural fox populations is well known, but it remains to be seen how well it would work in urban settings and whether the economics would make it a viable option, especially given the widely divisive issue of foxes and their control.
Methods of control and their problems
“In Scotland, only the cities of Edinburgh (population 430,000) and Glasgow (population 629,500) experience [more than] 50 complaints per year; the majority (56%) of urban areas receive [fewer than] 25 complaints per year”
Surveys by Bristol University have shown that most of those questioned had a positive opinion of foxes – the most recent of these was a survey of 4,000 households across Britain in 2002 that found, of the 3,409 respondents who had a view on urban foxes, only 8.5% actively disliked the animals. Similar studies in Europe suggest that opinion is typically either positive or ambivalent. Nonetheless, a recent vox pop, conducted by Opinions Matter (in association with the London Wildcare Trust) in the wake of the fox attacks in London, found one-fifth of the 1,000 people questioned were now afraid of wildlife and one-third no longer put food out in their gardens, even for the birds. It seems the most unpopular garden animal was the magpie (Pica pica), followed by the fox; 20% of the respondents considered that foxes were a menace, vicious and carried disease. Indeed, even in surveys that yield broadly positive views, people often express fears of disease as a reason for controlling foxes and this is not unfounded -- they are a principal vector of rabies in Europe and North America -- but the risks are low in the UK. With the exception of mange, which can be transmitted to dogs and humans (although it is easily treated in dogs and lasts only a few days in humans), there are very few reported cases of diseased foxes from Britain and this country is still free of rabies. More information on the diseases carried by foxes can be found in the main fox article but, suffice to say, even though some significant parasites are relatively common in foxes, there is no evidence that they are a threat to public health. Some 50% of Britain’s foxes carry the Toxocara canis roundworm that can be dangerous to pregnant women, for example, but there are no data to suggest foxes are a significant source of infection for dogs or people and the disease is rare in humans. Similarly, the hyatid tapeworm Echinococcus granulosus isn’t widespread (and may actually be declining) in Britain’s foxes, while the related cyclophyllid tapeworm E. multilocularis is absent from Britain.
Culling has various logistical problems too. The most effective method of control is shooting but, as you might imagine, there are various laws and bylaws that strictly control the use of fire-arms in urban areas. It is also often difficult to establish ownership for areas of derelict land that foxes often favour and to obtain permission to enter gardens if the owner is ‘pro-fox’ – trespass with a weapon is an offence under the Criminal Law Act of 1977. Shooting must be carried out by experienced and licensed personnel, with an appropriate calibre weapon (not an air rifle), and will typically require the use of a long-dog to collect any foxes wounded but not killed outright – the notion of a wounded fox slinking away to die of gangrene seems, incidentally, to be unfounded and foxes appear to heal remarkably quickly. Consequently, shooting is often limited to specific gardens and larger areas of public open ground (parks, cemeteries etc.). In urban areas, as MAFF found, there is the potential to shoot cats by mistake (they’re about the same size, move in the same way and are active at night) and this is an offence under the Criminal Damage Act of 1971. Snaring is often employed in rural locations, but is largely impractical in urban areas. Under the Wildlife and Countryside Act of 1981, there is currently only one form of snare that is legal in Britain and snares are highly unselective, even when set with care. In his 1984 paper, Harris references an RSPCA survey that found 86 foxes, 80 cats, 30 badgers and 15 dogs (to name a few of the species) in the snares they surveyed. By law, foxes can no longer be gassed or poisoned.
Trapping foxes for dispatch is very time consuming and may require substantial public cooperation, although it is widely used by pest control companies, but provided the animal is subsequently shot by a competent marksman, this is a humane method of removing ‘problematic’ animals. It is, however, generally ineffective for the widespread and intensive culling required. Foxes may occasionally be trapped for relocation, but the territoriality discussed earlier makes it unlikely released animals fare well (and thus might be illegal under the Abandonment of Animals Act of 1960) and there is the potential to move diseases (i.e. sarcoptic mange) into previously healthy populations.
Finally, work has been done in Australia -- where foxes were introduced during the 1870s and have since become a significant predator of the country’s native wildlife -- on the possibility of sterilizing foxes to reduce their populations. The premise is simple: sterilized foxes defend the same territories as fertile ones (thereby preventing immigration), but cannot breed and thus a vital source for the population is cut-off. Indeed, fertility control (and especially a method known as immunocontraception) has shown promise as an alternative to lethal control and, as such, has been advocated on welfare grounds. Unfortunately, owing to various technical issues -- including the number of animals that would need sterilizing in order for the scheme to work and that individuals would need multiple treatments -- have resulted in Australia abandoning research on immunocontraception in foxes.
Reasons for implementing fox control
We have seen increased public concern over the numbers and behaviour of urban foxes and the perceived lack of support from local councils. Any laws protecting the rights of animals (and Britain has several) are only going to be as successful as the public support they gather, and laws that appear to protect the threat and offer only expensive ways out (£100 to remove a fox) tend to generate disrespect. This situation could potentially lead to people taking the law into their own hands and using illegal methods (such as poisons, inefficient weapons and certain snares) to kill or deter foxes – although apparently debunked as a hoax, we saw the rather disturbing fox-killing ‘squad’ in London back in June. So, with a lynch mob clamouring in the streets, it could be considered a smart move for the local council to dispatch a pest controller to shoot a fox (maybe several) in the affected garden or area. Most people can appreciate that you’re unlikely to know for sure whether you’ve got the offending animal, but the point is that such action reinforces the public notion that any threat from foxes comes from isolated -- and identifiable -- individuals, meaning there's no need to wage war on foxes in general. Arguably, if the public finances support it, implementing a culling programme might, in general, serve to alleviate public concern, regardless of whether it is genuinely effective at reducing numbers (not dissimilar to the way people feel safer seeing more police officers on the street, regardless of whether there is any actual impact on crime rates). (Photo: Cage traps can be baited to attract foxes, which can then be shot or, occasionally, relocation. Relocation is, however, difficult and the method is time consuming and tends only to be applied to remove problem individuals.)
In addition to boosting public confidence, one could also argue that culling can be good for the fox population. It may seem counterintuitive, but sustained culling may promote genetic variability in fox populations. In a fascinating paper to Zeitschrift fur Saugetierkunde during 2000, biologists at the University of Siena in Italy reported that -- using enzyme and mitochondrial DNA samples from six hunted and three protected populations -- foxes in the hunted populations had significantly higher genetic variability than those from the protected populations. The theory goes that, in the protected population, a lack of mortality from either predators or lethal control results in the same individuals successfully defending the same areas for prolonged periods of time, thereby monopolizing matings. In the hunted populations, the rapid turnover of animals means new blood (and, more importantly, new genes) constantly flows in from outside. This is beneficial because, generally-speaking, the higher the genetic variability, the more viable a population is – think of the gene pool like a toolbox, the more tools you have, the better kitted out you are for whatever life throws at you. It should be noted that these data were collected from rural locations, where mortality is typically lower than urban areas and the social structures can be different, but the data do suggest culling can act as something of a ‘pseudo-surrogate’ for predation in the sense that it helps improve genetic variability.
The good, the bad and the ugly
There are some interesting dualities to arguments about the benefits of foxes in towns and cities. Take, for example, the case of foxes and rodents. On the one hand, I have heard councils advocate foxes for the pest control service they provide by helping control mice and rats. On the other hand, I have come across people who think foxes only encourage rats and mice by breaking open bin bags. So, which is true? Foxes certainly eat mice and rats (and other ‘pest’ species, such as rabbits, pigeons and gulls), but it is unclear whether they’re able to actually control the population. Off-hand, it seems unlikely that foxes could single-handedly control urban mice and rat populations, but they certainly appear to help. In rural areas, it has been shown that foxes can help keep rabbit populations down, although they cannot apparently cause a decline – so, if humans reduce the population initially, foxes can take over and keep it low. I have come across suggestions that, if we were to stop putting food out, foxes would devote more time to spreading our rubbish all over the streets. In fact, it seems more likely that they would spend more time hunting for rodents and birds. On the subject of breaking into bin bags, it seems unlikely that foxes encourage rats by doing this. Not only do foxes raid bins less frequently than many people suspect (in Oxford, the WildCRU team found most culprits of this behaviour were dogs and cats), but rats are more than capable of opening bin bags for themselves.
So, foxes do kill other animals that we consider pests and, of course, they eat any food discarded in the street that would otherwise be a meal for rats, mice, pigeons, gulls etc. They also provide many people with an invaluable connection to nature in a rapidly urbanizing world. Many of the e-mails I receive use adjectives like “beautiful”, “wild” and “enchanting” to describe encounters with foxes. Obviously there are many people who feel quite different, but to many, foxes represent a privileged glimpse into the natural world from the comfort of their kitchen window, office window or car. Reading through the stories sent in to BBC Wildlife Magazine, and published in their various ‘fox featurettes’, many are emotionally-charged, with people explaining how a special relationship they have struck up with a local fox has helped them through illness or personal tragedy. Indeed, it is no longer a ‘hippy’ concept that connecting with nature offers health benefits and, in a recent paper to the journal Health Promotion International, a team of Californian researchers noted how:
“Being in and caring for nature can be health promoting for individuals, families, communities, ecosystems and the planet.”
This is something that has been trialled in hospitals by placing recovering patients in rooms facing gardens and playing bird song. More recently, the NHS in Cornwall has been taking people suffering from mental health problems (i.e. depression and anger management issues) to Watergate Bay in Newquay and proving them with surfing lessons in a bid to improve their outlook and temperament.
Peace, man – the alternatives to lethal control
In summary, it seems fair to conclude that lethal control can only really be justified from a public confidence perspective as it is seldom economically viable and largely inefficient. Before any lethal control is introduced, information on the current state of the population to be culled is required so possible impacts can be estimated and progress can be assessed. After all, if you don’t know the state of the population, how can you establish whether your culling is having an impact? Foxes are wild animals whose behaviour is subject to change – a drop in complaints could be a response to other factors (changes in territory use, changes in food distribution etc.) and be un-related to culling effort. Ultimately, we need to look at deterrence with the possibility of intervention to deal with recurrently problematic individuals. It seems reasonable that councils should offer householders advice on fox deterrence, which would show a level of commitment to resolving the problem that appears to be lacking at present. (Back to Menu)
Q: Should we reintroduce large predators -- such as wolves, lynx and bears -- to control fox numbers?
Short Answer: No. It is reasonably well known that predators can influence populations of other predators via direct predation or displacement. Studies in North America, for example, suggest that coyotes can displace foxes, while data from Australia suggest dingoes may also displace foxes; neither species, however, have never been native to Britain, which would complicate any introduction. Additionally, there are data to suggest that, under certain circumstances, wolves and lynx will kill foxes and that, the latter at least, could do so in sufficient numbers to be considered a regulating factor. Nonetheless, the reintroduction of large carnivores is a highly contentious issue and unlikely to gain widespread public (especially farmer) support. Indeed, it seems likely that people who find it difficult to live with a relatively inoffensive mesopredator such as the Red fox, would struggle even more with macropredators like wolves or bears. Public perception aside, there are problems when it comes to using larger carnivores to suppress populations of smaller predators. Not only can we not control what animals these predators choose to eat, but tracking studies in Canada and parts of Europe suggest that wolves and lynx avoid human settlements; this could result in urban areas becoming fox refuges, worsening the situation. In addition, it seems probable that foxes may actually benefit from scavenging kill remains left by such large carnivorans. Thus, predator introduction is unlikely to be either practical or effective as a means of mesopredator, especially urban fox, control in the UK.
The Details: In the wake of the cases of foxes biting people that made the headlines earlier this year, there have been calls for local authorities to control what many perceive as an increasing Red fox population. Various suggestions have appeared in the media, including sending out marksmen to shoot the animals and making local councils responsible for their trapping and removal. The questions of whether the population really is increasing, whether we should be enforcing some form of control, and what factors influence fox numbers have been discussed in related QAs, but it seems that there are many people who are fervid in their belief that there are no controls on Britain’s fox population leading to suggestions that we should reintroduce large carnivorans (members of the Carnivora order) to regulate numbers. I find it hard to believe this is a serious suggestion -- at the very least, it seems a little like, to paraphrase David Bowie, trying to put out fire with gasoline -- but it does raise an interesting question: if we still had large predators (wolves, bears and lynx, for example), could they control fox numbers? It is, after all, well known that the removal of top predators can result in populations of smaller predators increasing – this is a process known as mesopredator release.
Before we look at these large carnivorans (or ‘macropredators’) in greater detail, let us first approach the subject of population control by predators. Most people with a basic grounding in biology understand that predators can affect the numbers of their prey, but how do predators influence the populations of other predators? There are two main factors to consider here and they are not necessarily mutually exclusive. The first, and perhaps most obvious, method is when the predator becomes the prey. Take the example of the pike (Esox lucius); pike are large predatory freshwater fish that will take a variety of prey including trout and other pike – in their lacustrine ecosystem they are apex predators (i.e. at the top of the food web). The fact, however, that they are at the top of their lake’s food web, doesn’t mean that nothing eats them. In Scotland, both trout and pike are prey of the osprey (Pandion haliaetus), a predatory raptor. Consequently, we have one predator (a bird of prey) that not only competes for food (trout) with, but also directly predates, another large predator (pike) – this is a phenomenon called intraguild predation or superpredation. So, here we have ospreys potentially limiting the population of another major predator through intraguild predation.
In the above example we have one predator preying on another, but killing may not always be necessary and, even where killing is a feature, it may not result in consumption of the carcass; there are plenty of examples of large carnivorans killing smaller ones but not eating them. Grey wolves (Canis lupus) will, for example, kill coyotes (Canis latrans) but show no interest in the carcass, while Brown bears (Ursus arctos) are known to kill smaller Black bears (Ursus americanus) but consume very little, if any, of the carcass – indeed, it is comparatively uncommon for carnivorans to eat each other. So, what is the aim of this killing? Why go through the energetically expensive and risky process of killing something you don’t plan to eat? The answer is the maintenance of resource security, via a phenomenon ecologists refer to as competitive displacement. Put simply, competitive displacement occurs when an animal cannot survive in an area because the resources are dominated by another animal. In the case of the wolves, killing coyotes means that a potential competitor is removed and thus there are more resources for the wolf pack. It is important to note that killing may not be predominant in the interactions -- just monopolizing food sources can be sufficient to stop another predator getting a ‘foot hold’ -- and although the definition makes the process sound very black-and-white, in reality it can be subtle. Wolves don’t necessarily completely exclude coyotes from their ranges, for example, but there is a significant negative relationship between the species (i.e. there are fewer coyotes in wolf strongholds than in areas where wolves are scarce or absent).
So, predators can influence the distribution and numbers of other predators, either through direct predation, or competitive displacement, or a combination of both.
The fox and the hound
Fox cubs can fall prey to various larger carnivores, including badgers, birds of prey and even domestic dogs and cats. Adult foxes, however, have relatively few predators and, for the most part, predation comes from the skies. Golden eagles (Aquila chrysaetos) are more than capable of killing an adult fox and, although there is some debate as to the size of prey a bird can fly off with, several authors (including Lea MacNally in his Highland Deer Forest) have reported foxes in eyries. I don’t have any data specifically for Scottish eagles -- not least because most studies lump foxes as part of ‘other mammals’ in datasets (although in a 2005 information note by the Forestry Commission, foxes are listed as ‘occasional’ prey of eagles in the Hebrides) -- but elsewhere Red foxes comprise up to 10% of the diet. Fox remains have also been found during dietary studies of Eagle owls (Bubo bubo), although with a much lower frequency (less than 1%). It should also be noted that remains in the diet doesn’t necessarily imply predation; scavenging is an equally, if not more, likely explanation. Furthermore, the range of these raptors in Britain is highly restricted and there is certainly no suggestion that either species hunt in urban areas.
Foxes will displace other foxes and there are numerous descriptions of fatal fights between them. There are also instances of badgers occasionally predating adult foxes; there are reports in the literature of fights, and during social interactions it appears that badgers are dominant. Nonetheless, any fatalities appear to be rare and in most cases the foxes simply keep their distance and come to no harm. There is, nonetheless, an interesting proposal that badgers may influence fox numbers through competitive displacement. In 2008, a team of biologists at the Central Science Laboratory (now part of The Food and Environment Research Agency) in York published a paper in the journal Biology Letters suggesting that where badgers were controlled, fox numbers increased. The data, collected during the Randomized Badger Culling Trials (RBCT) show that in the regions where badgers were heavily culled to assess the impact on bovine tuberculosis outbreaks, fox numbers increased by around two animals per sq-kilometre. The suggestion is that badgers and foxes compete for many of the same resources (i.e. suitable den sites and food such as earthworms) and when badger numbers decline it leaves more room and food for the foxes. This is, of course, only a single study and one should be cautious about making proclamations, but it is an interesting suggestion that warrants further investigation, especially given that badgers are an increasingly common sight in our towns and cities.
So, we’ve seen that although foxes are subject to some direct predation in Britain, it is unlikely to be a significant factor in regulating their populations, especially in urban environments. Thus, is there a need for other large predators to step in and take up the challenge?
Dances with wolves
There have, over the years, been several calls to reintroduce wolves to Britain, usually as a means of controlling deer. One of the first such suggestions was made in 1986 and called for them to be released on the Isle of Rum, off the west coast of Scotland, to regulate the Red deer (Cervus elaphus) population. More recently, in 1999, Aberdeen University zoologist Martyn Gorman called for wolves to be reintroduced to the Scottish Highlands with a view to controlling the deer that were causing damage to the commercial plantations. It has been suggested recently that, if wolves were present in Britain, they would also act to control the fox population, but there is surprisingly little evidence to support such a claim. Indeed, wolves may actually be beneficial to foxes.
There are no recent studies on fox-wolf dynamics, but we do have data from a long-running study conducted on the Isle of Royale, a large island in North America’s Lake Superior. In a 1966 report on the wolves of Isle Royale, L. David Mech described how he witnessed a wolf chase, catch and kill a fox that had passed a moose kill. In the report, Mech also noted another two instances where foxes were seen to flee instantly upon sensing wolves. Not all encounters, however, were either fearful or fatal and Mech described two where foxes (one asleep near a pack feeding on a moose and another where a fox approached a lone wolf at a carcass) were tolerated by wolves. Earlier studies -- also cited by Mech -- have found a similar level of tolerance between the species and, in 1957, US National Park Service biologist James Cole observed foxes approaching wolves at kills on two occasions, showing little fear or apprehension. Similarly, in a 1944 report, wolf biologist Adolph Murie observed foxes in the presence of wolves and even scavenging from their kills, concluding that:
“the relationship between the wolf and the fox seems to be one of mutual gain.”
Indeed, it seems that wolf kills may represent an important food source for foxes, especially during the winter when their regular prey is scarce; there are reports of foxes following wolf tracks in search of a potential meal. In a 1970 paper to the American Midland Naturalist, University of Wisconsin ecologist Wendel Johnson reported that moose remains were most common in the winter scats of foxes living in the Isle Royale National Park and that the meat was probably scavenged from wolf kills. In the paper, Johnson wrote:
“Foxes visit nearly all the carcasses left by wolves and were often seen feeding on these while wolves were still in the area.”
These data deal with fox-wolf interactions in rural areas and the recent outcry has been regarding urban foxes. Even if we did have evidence that wolves could regulate fox numbers, there is evidence that their urban influence could be limited. When most people think of wolves, they think of an iconic ‘wilderness species’ and tracking studies generally support this notion. As Derek Yalden puts it in his 1999 book, The History of British Mammals, “wolves are scared of people”. Some recent data suggest that wolves may be venturing into the city limits of North Bay in north-east Ontario and a study is underway by the Urban Wolf Study Group (based, in part, at Nipissing University) to use DNA analysis and telemetry to find out, but it has been proposed that these animals may actually be wolf-dog hybrids. Similarly, in their 2003 book Wolves: Behavior, Ecology and Conservation, David Mech and Luigi Boitani note that wolves in parts of India are known to den in urban areas. Nonetheless, the majority of tracking studies in North America and parts of Europe (e.g. Spain and Italy) have shown that wolves actively avoid contact with humans. Recently, concern has been raised that wolves are abandoning some of the otherwise suitable habitat in Jasper National Park (in the Canadian Rocky Mountains) because of disturbance caused by hikers. Anecdotal evidence from naturalists and photographers working in Yellowstone National Park (north-west America) suggest that the wolves are very shy. With this in mind, it is very difficult to see how releasing wolves into Britain’s countryside could regulate foxes living in urban areas. Indeed, observations that wolves typically avoid human settlements implies that, even if wolves were introduced to Britain and foxes did actively avoid them, our towns and cities could become enemy-free space for foxes (i.e. a safe haven from the predators roaming the countryside)!
There are, to the best of my knowledge, no studies looking at whether Brown bears influence sympatric fox populations. The only reference I have come across is the description of an incident during June 1940, where a fox followed and watched a bear digging out Ground squirrels for more than an hour-and-a-half, as recounted by Mech in his 1966 report. At no point did the bear seem bothered by the fox’s presence, although the fox was observed to keep a safe distance. The two species may compete for some of the same prey (e.g. small mammals and berries), but both are highly catholic feeders and competitive displacement seems unlikely. Likewise, Brown bears may chase foxes from their kills, but they don’t appear to actively predate them and it seems probable that, as with wolves, foxes may ultimately prosper from scavenging kill remains.
The missing lynx
When, in 1994, Eric Lindstrom and nine colleagues argued that the increase in Scandinavia’s Red fox population since the mid-1950s was at least partly a response to the absence of natural predation, it was primarily lynx (and to a lesser extent wolves) to which he was referring. Indeed, based on work carried out in Sweden during the 1960s and 70s that found a negative spatial relationship between lynx and foxes (i.e. where lynx were present foxes were scarce), Lindstrom and his co-workers predicted that the fox population would decline if large carnivoran populations were allowed to recover. Indeed, tracking studies of lynx in the Swiss Jura Mountains by a team of biologists -- led by Anja Molinari-Jobin at Switzerland’s KORA Carnivore Research Centre -- during the mid-to-late 1990s recorded unprecedented predation of foxes. The zoologists found annual average kill rates of 1.5 and 2.3 foxes per lone female and lone male lynx, respectively – it seems that subadults killed more foxes (6.1 each, on average) than the adults and each family group killed just over 13 foxes. Overall, each lynx in the study killed just fewer than five foxes; 37 foxes were killed during a total of 1,156 days of lynx observation.
More recently, conservationists have studied the frequency and patterns of lynx predation on foxes in the Grimso Wildlife Research Area of southern boreal Sweden. In a paper to the Journal of Zoology during 2006, Swedish University of Agricultural Sciences biologist Jan Helldin and two colleagues reported the results of their radio- and snow-tracking study of foxes in this lynx habitat between 1995 and 2004. They caught and tagged 20 adult foxes, of which three (15%) were killed by lynx. The researchers snow-tracked lynx and found seven dead (lynx-killed) foxes and, based on the track patterns, another seven unsuccessful fox hunting attempts; each lynx was calculated to have killed an average of 1.3 foxes. Despite the relatively low predation rates the authors concluded that the lynx were an ‘additive mortality source’ and thus had the potential to cause a decline in the fox population. Indeed, in their paper, they concluded:
“The results from our study suggest that the present deficit of large carnivores over most of their former ranges may have resulted in an over-abundance of red foxes in many areas. Allowing large carnivores to re-establish may thus be an efficient way of limiting fox populations.”
There are, incidentally, some data from Canada suggesting that the lynx-to-fox ratio is an important factor regulating any population changes. It appears that a decline in foxes becomes more likely as the ratio of lynx to foxes approaches one (i.e. an equal number of both species). Fox depredation may also be influenced by season (presumably with underlying prey cycle influences) and, in a study of lynx prey in northern Belarus during warm (April-October) and cold (November-December) seasons, Vadim Sidorovich found that foxes appeared in the diet more than twice as often in warm seasons than in cold (4.7% vs. 2 %, respectively).
It should be noted that, as with wolves, lynx often make no attempt to consume the foxes they kill. In a 1999 paper to the journal Ecography, Danish zoologist Peter Sunde and two colleagues report that almost 40% of lynx-killed fox carcasses in their study were totally uneaten, whereas only 2% of the Roe deer (Capreolus capreolus) carcasses hadn’t been touched. Sunde and his co-workers concluded that lynx killed the foxes because they saw them as competitors, rather than as a potential meal.
So, lynx are the most promising carnivoran considered so far to actuate a decline in the fox population but, as with wolves, there are the issues of benefits and refuges to contend with. Helldin and his colleagues noted that there has been a recent change in the foxes’ habitat preference in their study area, with a selection for the areas of farmland and human settlements that lynx do not inhabit. Thus, although it seems lynx can regulate some rural fox populations, we are again struck by the potential for urban areas to become a predator refuge for foxes. Moreover, in a 2007 paper to Wildlife Biology, Helldin and Anna Danielsson reported on the changes in Red fox diet since the colonisation of lynx in the southern Boreal forests of Sweden. Helldin and Danielsson noted that foxes were common scavengers of lynx kills and often followed lynx trails in search of a carcass. The biologists described access to the carcasses of Roe deer killed by lynx as “an important, stable food supply for red foxes”, being the single most important food item all year round. Snow-tracking on the Moosehead Plateau of western Maine (USA) between 1979 and 1982 commonly found bobcat (Lynx rufus) tracks in traditional fox ranges and suggested that both species visited a deer carcass in the area.
So, if neither wolves nor bears nor lynx are likely to be beneficial in controlling urban foxes, are there any large carnivorans that might? There is one, but it was never native to Britain.
The relationship between foxes and coyotes has been studied in detail by U.S. Fish and Wildlife Service biologists Alan Sargeant and Steve Allen. In a 1989 paper to the Journal of Mammalogy, the scientists presented 42 accounts of coyote-fox interactions, predominantly from North Dakota, made between 1970 and 1985. The majority of the accounts (71%) described aggression by coyotes towards foxes, with seven detailing the killing of the fox and five telling of a single coyote chasing a fox; additionally, three accounts told of eight fox cubs from six earths having been killed by coyotes. Interestingly, however, it seems that not all interactions end in aggression and three accounts told of coyotes and foxes simultaneously occupying the same breeding den, one account of a coyote and fox feeding simultaneously on a cow carcass, and a case of a coyote that spent several minutes watching a couple of foxes mating from about 100m (328 ft.) before leaving. Nonetheless, with the exception of one person who reported that he often saw coyotes and foxes apparently unconcerned with each other, the majority of reports received documented some form of hostility towards the fox. It is interesting to note that, despite the documented interactions, radio-collared foxes are apparently rarely killed by coyotes and an earlier study by the same authors found that none of the 22 foxes collared and tracked for 2,518 days in North Dakota fell foul of the resident coyotes. A subsequent study of coyote-fox interactions in Yellowstone National Park, Wyoming, revealed a more even distribution of displacement and tolerance, finding that coyotes tolerated foxes in just over half the encounters and either deterred or actively displaced them in the other half. Apparently, the sight of a family of coyotes lying up near a carcass was sufficient to deter approaching foxes.
The studies to date have documented coyotes displacing foxes in rural habitats and the situation is unclear in urban areas. In their contribution to the 1982 compendium Wild Mammals of North America, David Samuel and Brad Nelson point out that foxes tend to do well around human settlements, probably as a result of their being fewer coyotes. Obviously, this was nearly three decades ago and today coyotes are far more common in urban areas. Nonetheless, there still doesn’t appear to be any data on their influence on urban fox populations and although, in their chapter in the 2010 Urban Carnivores compendium, Stanley Gehrt and Seth Riley make note of the coyote’s general tendency to displace foxes, there is no specific reference to the urban scenario. Regardless, coyotes do seem to be problematic for foxes and a recent decline in Illinois’ (eastern USA) foxes has been attributed, in part, to the eastward expansion of the coyote.
So, why should coyotes be less tolerant of foxes than the other species we’ve considered? The answer is food. What we see is a scale of intolerance associated with perceived competition. Wolves work together to bring down large prey (e.g. deer) that is simply too big for a fox to tackle and, aside from scavenging the odd bit of meat from a carcass, foxes don’t pose a threat to the wolves’ food supply. Similarly, lynx take Roe deer above the size limit foxes could manage; they also, however, feed heavily on Snowshoe hares (Lepus americanus), which is an important prey item of the fox. Thus, the fox represents greater competition for the lynx than it does to the wolf and several studies in North America have now shown that as snowshoe hare populations decline, the incidents of lynx killing foxes goes up. Foxes and coyotes, on the other hand, feed largely on the same prey. Both species primarily eat small mammals -- including squirrels, rabbits, mice and voles -- along with birds, insects and carrion and, in urban areas, both will take human food. In short, coyotes and foxes occupy very similar niches and consequently, to coyotes, foxes represent a significant competitor. A coyote, therefore, has more reason than either a wolf or a lynx to ensure the foxes don’t hang around to use up resources that will otherwise be theirs. Indeed, stable isotope data collected by researchers at the University of Illinois suggest that the presence of coyotes forces foxes away from their preferred prey of rabbits (which they eat in areas without coyotes) and on to rodents, birds and insects. So, coyotes have good reason not to want foxes around and -- considering the difference in size (they can be more than twice the weight of an average adult fox) and that coyotes are often found in pairs or packs averaging six animals -- the predominantly solitary foxes have good cause for avoiding them.
“…the abundance of wild dogs sets and upper limit on the abundance of foxes, but does not fully determine fox abundance.”
Dingoes are known to enter urban areas at night and so could potentially have an impact on urban fox numbers (although the data are lacking) but, as with coyotes, they have never been native to Britain, which would severely complicate any introductions.
Predators on the doorstep
Over the years, many have tried to get an insight into how the public feel about the idea of sharing the countryside with large carnivores. Probably the most widely-known survey was that initiated by professional wildlife photographers Peter Cairns and Mark Hamblin – together they launched the Tooth and Claw project in a bid to gain an understanding of how people felt about predators in Britain. In the last six-or-so years, Peter and Mark have spoken to a wide range of people and organisations associated with predator management both here and abroad, and widely circulated a sizeable questionnaire to members of the public asking their views. I don’t want to go into much detail about the relationship between humans and predators, but the findings of the Tooth and Claw survey make fascinating reading; the reader is directed to Peter and Mark’s 2007 book Tooth and Claw: Living alongside Britain’s predators for an authoritative and incisive account.
In general it seems that the public as a whole have a somewhat fickle opinion of wildlife. Most people who completed the survey, for example, agreed that we had a responsibility to reintroduce wolves to the Scottish Highlands, but most in favour lived in the south of England. Thus, there is a tendency for people to tolerate animals until they become a problem for them. Effectively, it goes something along the lines of: ‘I’d like to see wolves reintroduced to Britain, provided they don’t pose a problem for me, my friends, my family or my pets/livestock’. Added to this, many of us have become dissociated from the practice of hunting and how crucial it is for a predator; this can lead to an element of double-standards. In an article to The Countryman during November 2007, Peter Cairns recounts the story of a lady in the same hide as him watching Golden eagles in a Scottish glen who relayed with great excitement how she’d watched an eagle swoop in and catch a rabbit, which it repeatedly dropped from a great height until it eventually carried it away to eat. Later that evening, Peter joined her birdwatching party for dinner and recalls how she condemned a sparrowhawk (Accipiter nisus) for killing ‘her’ garden birds, and proclaimed that someone should do something about it. In the article, Peter sums up well, writing:
“It is clear that such polarised perceptions have developed rather than being intrinsic. Economics invariably play a part. Those species whose prey is valuable to us have been persecuted over many centuries and such ‘management’ continues today.”
This brings us nicely to the first point about the reintroduction of large predators: we cannot control what they decide to eat and in the event that they begin taking livestock or pets there would be an outcry. The taking of livestock and, in the very worse-case scenarios, the attacking of people has a habit of generating public fear and mistrust that even the most reasoned argument will struggle to combat. However rational a given person may be about the situation, humans are by nature a social species and public opinion can readily gain momentum – just look at the hyperbole about urban foxes recently. I am reminded of one of my favourite quotes of all time, as delivered by Tommy Lee Jones in the movie Men in Black, which goes:
“A person is smart. People are dumb, panicky dangerous animals…”
It is certainly true that people co-exist with large carnivores elsewhere in the world, but having lived in such a predator-free landscape for so long, this is a mentality that many Britons need to learn. Managing predators is arguably more about managing people’s attitudes than the animals themselves and, as Latvian ecologist Zanete Andersone-Lilley told the Tooth and Claw project:
“People are alienated from nature, they don’t see themselves as part of it anymore, hence it is regarded as dangerous, something to be controlled.”
Obviously this is a broad generalisation and there are a great many people who are still very much in tune with Nature, but the point remains that humans, as a species, have lost many of the important bonds they once shared with the natural world and this presents a barrier to any introduction of predators to the public landscape.
Even if public opinion could be successfully won and a reintroduction started, it is difficult to predict how successful they will be. There are very few truly wild places left in the UK and it is unclear whether the level of disturbance across the rest of the country would lead to predators becoming restricted to these remote areas, thereby effectively negating their desired impact. This seems particularly applicable to predators such as wolves and lynx which tend to avoid human contact unless habituated with food.
Q: Why do foxes kill their own young and the young of other foxes?
Short Answer: This is a behaviour called infanticide. Infanticide is broadly defined as the killing of young offspring by a mature individual of the same species (a conspecific) and is relatively common among animals. The reasons for infanticide are poorly understood, but several theories have been offered in explanation. The Predation Hypothesis (PH) suggests the killing is done purely to obtain food, while the Resource Competition Hypothesis (RCH) considers that infanticide removes potential competitors, thereby leaving more food for the killer and their offspring. The Adoption Avoidance Hypothesis (AAH) suggests that killing the young of others is a way of preventing alloparental behaviour (where a mother adopts a youngster that isn’t hers) while there are other, so-called, non-adaptive explanations, which consider there’s no evolutionary benefit and the young just fall foul of increased aggression, or some aberrant behaviour, in adults (a wrong place, wrong time deal). The most oft-cited explanation is the Sexual Selection Hypothesis (SSH), which suggests that males may kill young sired by other males to prevent them raising kids that aren’t their own and to bring the female back into oestrous sooner. No single theory fits all observed cases of infanticide, although the PH fits many. Unfortunately, it is often difficult to decipher the relationship between infanticidal individuals and their targets, which further complicates explanations. The SSH fits well for many mammals, especially big cats like lions, but less so for foxes, as vixens don’t come back into oestrous until the following season. In captivity, infanticide seems best explained as a non-adaptive behaviour, while the RCH and PH appear a better fit for wild observations.
The Details: The killing of young is a practice known as infanticide and, although literally applicable to the killing of any immature animal by any other, it is more commonly evoked to mean the killing of newborn (or otherwise dependent) young by an adult of the same species (i.e. a conspecific). Infanticide is often broadly divided into two categories -- ‘parental’ and ‘non-parental’ -- depending on whether a mother/father is involved and the practice as a whole is a widespread, if poorly understood, phenomenon. In a 1998 paper to the journal Biological Reviews, for example, Boston University biologist Luis Ebensperger listed 93 species of mammal in which non-parental infanticide had been documented, either in captivity or the wild; Ebensperger's list included wolves, bears, badgers, monkeys, apes (including humans) and even rabbits and deer. Infanticide differs from the more commonplace intraspecific killing (where animals kill members of their own and other species) and cannibalism; young are specifically targeted and the carcass is not always eaten (indeed, food may not necessarily be the apparent motive for the killing).
Infanticide appears to be a complex behaviour and there is no single theory that appears applicable to all cases, although most cases can be explained by one or more of the five main presiding theories. I don’t wish to get too wrapped up in the details of these theories and so I shall only provide an overview of each here before we look at where foxes fall.
Predation Hypothesis (PH): This hypothesis suggests that animals engage in infanticide purely for nutritional gain (i.e. to obtain food) and predicts, accordingly, that the killed youngster will be eaten (i.e. predicts cannibalism); infanticide should thus be more common when conditions are bad and food is scarce. Much of the infanticide documented in chimpanzees and rodents (including squirrels and mice) seems to fit quite nicely within this category – in rodents cannibalism is most often observed when the female is lactating (and is thus in dire need of energy).
Resource Competition Hypothesis (RCH): The idea behind the RCH is that the perpetrator kills the youngsters of another individual in order to give either itself or its offspring a greater share of a limited resource (i.e. food, shelter, water etc.). There are several predictions of the RCH, but we would expect infanticide to be most common when resources were tightly stretched. One suggestion is that a dominant female may suppress the breeding of subordinates in her social group by killing their offspring, thereby ensuring that hers get the best possible start. In a paper to the Journal of Mammalogy during 1992, Joachim Kunkele described infanticide among wild rabbits (Oryctolagus cuniculus) in Germany, concluding that it was the result of females competing for a limited numbers of breeding burrows. Similarly, primatologists at St Andrews and Harvard Universities have observed coalitions of female chimpanzees (Pan troglodytes) killing infants of neighbouring troops as they compete for limited resources in Uganda’s Budongo Forest. The RCH has also been put forward to explain infanticide in wolves (where the pups of subordinates rarely survive for more than a couple of days) and dingoes – in the latter species the dominant female will kill the cubs of any breeding subordinate, after which the subordinate devotes her energies to suckling the dominant mother’s cubs. Thus the breeding female benefits because not only are there more barren females to help provide for her young, there is also less competition for food, meaning her litter don’t have to share with any others in the group.
Adoption Avoidance Hypothesis (AAH): This theory suggests that infanticide evolved to prevent alloparental behaviour – in other words, to prevent adults taking over (or playing a significant role in) the raising of kids that aren't their own (literally adopting someone else's kid). Alloparental behaviour can include animals other than the mother or father (although usually related) suckling, playing with and guarding young in their social group. Alloparental behaviour is fairly widespread and common among social mammals, although there is quite a body of evidence from the pinnipeds (seals and sea lions) suggesting that pups are killed when they get separated from their mothers and try to suckle from another female on the beach.
Sexual Selection Hypothesis (SSH): This is perhaps the most off-cited explanation for infanticide (and is commonly featured in wildlife documentaries). The SSH argues that a male will kill the dependent offspring of a female for two reasons: to prevent him providing for offspring that aren’t his own and/or to bring a female back into oestrous so he can mate with her. Mammals generally don't ovulate while they're lactating, so if a male kills a female's young, she stops lactating and is able to become pregnant again. Perhaps the best example of this is found in lions and, according to research by Craig Packer and Anne Pusey at the University of Minnesota's Lion Research Center, killing existing cubs allows a male to sire cubs up to eight months sooner than if the cubs were spared.
Non-adaptive Hypotheses (NAH): In evolutionary biology, behaviour is considered "non-adaptive" if it doesn't help get the animal's genes into the next generation. There are several theories that are grouped under the umbrella term non-adaptive and they suggest that infanticide may come about through traits such as a general increase in aggressiveness or that death may be accidental or come about from aberrant behaviour by the adult.
The infanticidal fox
“almost invariably started with tail-biting, from a few hours to a couple of days port-partum. Some vixens bit off the tails gradually, 1-2 cm at a time, until virtually nothing was left.”
It appears that infanticidal vixens often bit off the tails of all their cubs, even though not all were later killed – in most cases the vixens ate the cubs they killed. Braastad also observed a tendency towards subsequent infanticide; if infanticidal vixens were allowed to breed the following year, they were likely to exhibit the behaviour again. Analysis of the infanticidal vixens’ behaviour, compared to that of non-infanticial individuals, suggested that stress could’ve been the cause and Braastad concluded that infanticidal vixens felt more tense and insecure than ‘normal’ ones.
In a more detailed study, published in the same journal six years later, Braastad and his colleague Morten Bakken described infanticidal behaviour in their farmed foxes and compared new mothers (primiparous) to more experienced (multiparous) vixens. The biologists recovered the bodies of 54 dead cubs, 41 (76%) of which had been bitten and presumably killed by their mother. Many of the same behaviours reported in the 1987 abstract also appear here, although there are some interesting disparities between the two groups in this study. Primiparous vixens tended to kill their cubs instantly with a bite to the skull, while multiparous vixens were more likely to kill their cubs through a gradual process that began with tail- and limb-biting. Indeed, primiparous vixens were observed to abandon or kill their cubs significantly earlier than multiparous females, although there was no significant tendency for primiparous vixens to be more likely than multiparous females to commit infanticide in the first place. The researchers also found that, although there was no obvious pattern suggesting a vixen is either always or never infanticidal, a vixen that was infanticidal in one year was more likely to be infanticidal in subsequent ones. As before there was a tendency for dead cubs to be treated as prey and “were sometimes buried under wool tangles, only to be dug up a few hours later and eaten”. Braastad and Bakken point out that, in the wild, several of the infanticidal vixens were unlikely to have bred, owing to their low social status, and this may indicate that social stress is an important factor. Indeed, Braastad had previously demonstrated that vixens of any age were generally calmer and showed lower cub mortality when provided with more secluded breeding boxes with narrower entrances and also when kept away from other foxes. The authors concluded that low social status increases ‘fear level’ and that successful reproducers have lower fear levels than infanticidal ones – they suggest that, as much of the tail-biting occurred during grooming, more agitated vixens may be rougher with their cubs and the resulting bleeding tail may attract more licking and biting.
It’s always difficult to take data collected from captive animals (especially the highly artificial environment of a fur farm) and apply it to wild individuals, but the Norwegian data do suggest that if the social hierarchy of wild fox groups suppresses subordinate breeding in the first place, infanticide should be rare. Whether or not a vixen breeds in any given year is largely a result of the level of mortality the population is subjected to. In populations where mortality is high, stable family groups cannot become established and foxes tend to live in pairs; in such cases, most vixens will breed. Where social groups can form, daughters of the dominant vixen may remain on the territory for several years, during which time they’re unlikely to breed (there are exceptions, but typically only one vixen in a group will succeed in raising a litter). Under conditions of low mortality, around one-third of vixens will be barren. Braastad’s data, as well as that collected for various species, suggest that infanticide is most likely to occur during the first couple of weeks of life, which -- given that the vixen spends the majority (95% or more) of her time in or very close to the earth for seven to ten days after the cubs are born, and that the cubs remain underground until they’re four or five weeks old -- makes it difficult to establish how common it is in the wild because much presumably happens out of sight. This presumably accounts for the rarity of reports from the wild. Indeed, I am aware of only one other published case of maternal infanticide and this was under captive conditions, although they were more natural than those at the fur farm.
Between 1972 and 1979 Oxford University zoologist David Macdonald studied Red fox social groups on Boar Hill in Oxford. Professor Macdonald tracked and observed wild foxes, and closely observed hand-reared animals living in a one kilometre-squared (just under one-third sq-mile) enclosure containing vegetation and artificial earths. During his studies on the captive foxes, Macdonald described how one of the vixens had become very nervous and started running about the enclosure with one of her cubs in her mouth; eventually this rough treatment became too much and the cub died. All four of this vixen’s cubs died after being subjected to the same behaviour. Interestingly, this vixen had raised a litter the year before and had been a calm mother at that point – when the last cub of her second litter had died, the vixen returned to a calm composure. This observation lends support to Braastad’s suggestion that stress can be a progenitor to infanticide.
There are three cases of wild fox infanticide, from the literature, that I am aware of. The first was an account made by long-time fox watcher Mr R. Bigland and mentioned by Macdonald in a fascinating 1977 paper detailing fox food preferences. After finding the “largely devoured” body of a fox cub at an earth, the gentleman retired to a safe distance and watched. Mr Bigland described how he saw a vixen jump over a wall into the field where her earth was situated, carrying a dead cub in her mouth. The vixen approached the earth, dropped the cub and called her own cubs which then “fell upon the dead cub”. At this point the watcher approached and scared the cubs back underground, allowing him to examine the corpse – the body was larger than the cubs he’d scared away, still warm and appeared to have been killed by a bite to the back of the neck, at the base of the skull. Mr Bigland knew the local fox families well and immediately proceeded to the nearest earth in the direction from which the vixen had come (three fields away); upon arrival he found deep scratches in the soil around the earth entrance and several drops of fresh (uncongealed) blood on the roof of the entrance, suggesting that the cub had been dragged out. Unfortunately, the relationship between the two families was unknown.
The remaining two incidents were recounted by University of British Columbia student (at the time studying at Trent University) Valeria Vergara in a paper to The Canadian Field-Naturalist during 2001. In the paper, Vergara described two cases of infanticide in a fox family (an adult male, adult female and nine cubs) she was studying in Southern Ontario, Canada during May 1995. On the first occasion the mother was seen to flee from the earth a few minutes before an unknown adult fox (not previously recorded at the site) approached; the intruder adopted an aggressive stance (back arched, head and neck low) as it approached the earth and snarled at one cub, which crouched down and flattened its ears before retreating underground. With the cub out of sight the stranger resumed its trot until it came across a second cub, at which point it immediately resumed its threat posture. As the cub turned to retreat underground, the stranger stalked it very briefly before dashing towards it, seizing it by the neck and shaking it vigorously. The stranger “then scurried away carrying the limp body of the kit [cub] in its mouth”. The second incident took place three days later at the same earth when an adult approached, causing the cubs to crouch down (suggesting it was a stranger), and adopted the same aggressive posture as the previous stranger. The stranger seized a cub by the neck and shook it for a few seconds before the mother arrived back at the earth, causing the stranger to drop the dead cub, and chased the intruder away.
In addition to the published accounts, I have received several e-mails from readers describing cases of foxes killing other foxes and, one in particular from a couple living in south Essex, that clearly described infanticide. A portion of the e-mail is reproduced here, with their permission:
“It started about midnight, we heard like a crying noise but could not see anything in the garden we thought it might have been the badger. So we turned our bathroom light on and could see the fox in the middle of the garden laying down looking at the corner near the house, we watched for a little while because we could still hear crying, then the fox got up and walked away. About five minutes later we heard it call and then we saw a struggle the cub was trying to get away but the fox had it by the neck then we heard the crunch sound and the cub went limp. The fox then dragged it up the end of the garden looked around and left it. When we went in the garden in the morning the cub was still there no blood its neck had just been broken.”
Method in the madness
The maternal infanticide observed by Braastad, Bakken and Macdonald implies a non-adaptive behaviour – these foxes were kept in enclosures and supplied with food and water (and so presumably weren’t in need of food) and the death of the cubs appeared to have little impact on the mother, with the exception (in the case of the Oxford vixen) of calming her. The burying of the dead cubs by the farmed vixens does suggest that it was seen as food, but it doesn’t seem that hunger was the motivation behind the initial killing. Interestingly, in many cases of infanticide, especially in lions, consumption of the body is rare and, where it does occur, it rarely appears to be a result of hunger.
Recently, Willem van Heerder filmed some extraordinary lion behaviour at a private game reserve in South Africa. Following reports of two males fighting, van Heerder arrived on the scene and found the body of a recently killed cub (its spine was partially protruding, suggesting its back had been broken). A male approached the cub and licked it before picking it up and carrying it into some nearby undergrowth where it laid down and proceeded to eat it. Although infanticide is common among lions, reports of consumption of the cub are very rare and, particularly in this instance, so too are descriptions of the lion’s behaviour while it was eating the body. The lion was making the ‘grimacing’ facial posture (generally associated with flehmen) and a soft hissing noise, which -- according to Prof. Wouter van Hoven at the Pretoria University in South Africa -- is normally a subordinate display. van Hoven suggested that the facial posture and hissing implied that the eating of the cub was more symbolic than hunger-driven. I have seen similar footage where a female leopard cornered a python that had eaten her cub; she harassed the snake until it regurgitated the cub’s body, which she then sat and ate. I am not suggesting that the consumption of dead cubs by the fur farm vixens was in any way symbolic (there is no evidence to support such a conclusion); this is just to highlight that consumption may not always be a response to hunger – especially where infanticide is concerned. In the cases described Braastad and Bakken, it seems more likely that the vixen merely saw the dead cub as a potential food source and thus buried it for later consumption (waste not, want not, so to speak).
It is often suggested that one advantage of philopatry (living with your folks) for young vixens is that it allows them to gain experience of raising cubs by watching and helping their parents. If this is accurate, it follows that that primiparous vixens are potentially more likely to lose their first litter through inexperience than multiparous animals. Inexperience can take many forms but includes being too rough with the cubs, and could potentially explain the crushing of the skulls soon after birth if the vixen is overzealous.
It is always difficult to ascribe meanings to behaviours when you don’t know the relationship between the two individuals – this is especially true when attempting to interpret infanticidal actions. Nonetheless, the cases that we have seen among wild foxes imply a more adaptive explanation to infanticide. The infanticide described by Mr Bigland appears to fall under the predation hypothesis: the vixen was going to a nearby earth, killing cubs and bringing them back to feed to her own cubs, which were clearly hungry. There may be other, underlying, reasons for the behaviour (she may be less adept at catching birds and small mammals and thus the neighbouring cubs may represent a ‘soft target’) and there may even be an element of resource competition (killing the neighbouring cubs reduces competition for her own), but these require additional speculation. Ultimately, Occam’s Razor suggests this case is best explained by the PH.
The PH probably also explains the first case described by Vergara in Canada, although we cannot be certain. In the first case we know that the intruder left with the cub in its mouth and, although we don’t know what happened to it afterwards, consumption seems likely. The second case is a little less clear as the mother chased off the intruder almost as soon as the cub had been killed; we cannot be sure that the intruder would’ve left with the cub had the mother not returned. So, we have one case where the PH seems to fit best and another in which we simply cannot say – there are, however, elements of the strangers’ behaviour that are very interesting and imply there may be more to the interactions than the PH alone predicts. In both cases the stranger exhibited an agonistic body posture that, in my experience, foxes do not adopt when hunting their normal prey. Indeed, this aggressive posturing is something we commonly see during competitive interactions (i.e. when fighting with a potential competitor, such as a cat or another fox). Thus, there may be an element of the RCH to these encounters and, if so, it seems more logical that the RCH would be the principle explanation, with predation being a ‘side effect’.
In the case from Essex the explanation is highly elusive as we know neither the relationship of the adult to the cub, nor the behaviour of the two prior to the cub being caught. We do, however, know that the adult didn’t consume -- and given that it didn’t appear to get scared away from the carcass, presumably had no intention of consuming -- the cub. Thus, all we can say for certain is that the PH doesn’t appear to fit.
When considering the other hypotheses as explanations, we can be reasonably confident that the AAH doesn’t fit. On the contrary, alloparental behaviour is well known in foxes and, not only do the cubs often arouse considerable interest among barren vixens in the group, but the dominance statuses within the group may change when cubs are born, lasting until they’re weaned. In his study of the Boar Hill foxes, Macdonald wrote:
“Normally I could not distinguish the behaviour of non-breeding vixens towards cubs from that of the real mother…”
We have seen that most cases of infanticide in this species can probably be explained by the RCH, PH or can be considered non-adaptive behaviour. This raises the question of whether the SSH can be applied to Red foxes?
The SSH and the fox
So, infanticide works for lions, but the same principles do not apply to foxes. Foxes, like most mammals, are spontaneous ovulators, which means they have a fixed breeding season – more specifically, foxes are monestrous, meaning they have a single breeding season during the year. Indeed, vixens are receptive for only a few days each cycle, between December and February. Consequently, even by killing a vixen’s litter, a dog fox could not bring her back into oestrous. To ensure he is her mate in the following season, he would then need to stay with her until she comes back on heat (which, depending on the age of the cubs, could be eight months or more).
Thus, in conclusion we can say that the RCH and PH, as well as certain non-adaptive hypotheses, appear to explain some cases of infanticide in Red foxes. Our inability to ascribe relatedness in many cases, and that we only observe a fraction of the animals’ behaviour, means we cannot be certain as to the cause(s). Nonetheless, the AA and SSH do not seem to fit as explanations of infanticidal behaviour in these animals. (Back to Menu)
Q: Are foxes getting bolder and, if so, why?
Short Answer: Foxes in some urban areas do appear to be getting bolder, although there is a considerable amount of individual variation (even within the same family group). Foxes have been living in our cities since the late 1930s and many generations have grown up in an environment relatively free of persecution (very little active hunting or predation) and in which the majority of humans pose little threat to them. The response to humans being either neutral (posing no threat) or positive (a source of food) entities appears to have been that some foxes are no longer as wary of people as they were, perhaps, a decade ago. In rural locations, where foxes are still actively persecuted by farmers, gamekeepers and some hunts, the fox is still generally wary of humans. There is no evidence, of which I am aware, to suggest that bolder foxes are more aggressive. Problems arise when people mistake bold for tame and try to touch the animal.
The Details: Recent reports in the media have raised fears that urban foxes are becoming bolder; that they no longer have any fear of people, do not run from people and may actually approach. There have also been some recent suggestions in the press that foxes are unafraid of dogs and, in February 2011, TV presenter Ben Fogle reputedly “rugby tackled” a fox that chased his elderly Labrador near his home in London. With these reports comes the intimation that bolder foxes are more aggressive and thus pose a danger to people. To answer this question, we need to look at what boldness actually is and how it might evolve.
Boldness or shyness is usually ascribed based on how willing an animal is to approach an unfamiliar object; those that walk up to it immediately are the bold ones, while those that avoid it are considered shy. As you might imagine, however, it can be difficult to dump animals into just shy or bold categories because although a few might walk straight up to a new object and others may never approach something unfamiliar, some will bide their time for a while before approaching. In other words, different individuals within a species or population will respond differently to the situation. Now, early ethologists (people who study animal behaviour) believed that an animal’s behaviour was largely fixed and any individuality was simply fluctuation around this fixed point – in other words, it was ‘noise’ around the expected pre-programmed behaviour. We now know, however, that behaviour is plastic (i.e. it is flexible, not fixed) and is modified according to the animal’s experience and environment; in short, behaviour changes as an animal learns. In a fascinating 1995 paper to Psychological Enquiry, Pennsylvania State University psychologist Jay Belsky outlined his differential susceptibility hypothesis, which argues that individuals vary in the degree to which they’re affected by their environment and experiences – essentially, that some are more sensitive to what life throws at them than others. So, what all of this means is that, as an individual grows up it builds up a unique combination of behaviours (what we might call a ‘personality’). This is important because an animal must modify its boldness or shyness in order to make the best of its environment.
A fox that always walks straight up to novel object may strike it lucky if said object is a chicken or rabbit, but would be less fortunate if it was a coyote or badger. Conversely, a fox that never approaches a novel object is likely to dodge the business end of a badger, but at the same time is likely to starve. In either case, very bold or very shy animals are less likely to live to breed (and thus pass on their ‘very bold’ or ‘very shy’ traits). So, in the end, not only does it pay to be of ‘intermediate shyness’, but it also pays to modify how bold or shy you are based on your experience. Indeed, we express this with what ethologists and psychologists call the shy-bold continuum (SBC). As the name suggests, the SBC, is basically a scale -- from ‘shyest’ to ‘boldest’ -- along which individuals can be placed. Crucially, however, the SBC provides recognition that behaviour can be graded; that animals aren’t just bold or shy, some are bolder or shyer than others and how shy or bold they are changes according to their experience. Models and theories are good, but how do we translate them into actual behaviour. How do we look at a fox and say it’s bold or shy?
Animals, humans included, like their personal space and get nervous if unfamiliar animals get too close – ethologists call this their flight zone (FZ). The flight zone is essentially the space around an animal that, if encroached upon, will case the animal to move away – basically, it’s a measure of how close an animal will let you get before it runs away. Every animal has their own FZ and, because it’s based on how much of a threat the animal thinks you are and how fast it thinks you (and it) can move, FZs vary from object to object and individual to individual. We don’t need to know FZ theory in any great detail, just that as an animal gets more used to your presence, the FZ diminishes, allowing you to get closer. Here we have our first important point. It’s very easy to interpret a reduction in the FZ as the animal getting bolder, when it’s actually an indication of the animal becoming more comfortable with us. Indeed, it’s very rare for wild foxes to actually walk up to a person in the street. Again, our definition of boldness deals with how readily an animal approaches an object, not whether or not an animal runs away from it; that’s the flight zone. So, if anything, rather than bolder foxes, we’re seeing more ‘indifferent’ foxes, which just don’t really care that we’re around.
In contrast, a fox walking up to a farmer or gamekeeper in the countryside is likely to be met with the business-end of a rifle or shotgun! There’s a reasonably good chance that it won’t survive the encounter and thus, if such behaviours are firmly grounded genetically, its trait of ‘strolling up to passers-by’ won’t get passed on. Indeed, for a country fox, keeping out of sight and avoiding people is often the key to a long and healthy life and we see this in wild populations outside of Britain. In their 1982 comparison between the Red and Arctic foxes, Oxford biologists Páll Hersteinsson and David Macdonald noted how the latter species is 'tamer' outside Iceland, where it is hunted intensively for its fur; they also point out that, in Israel (where foxes are largely protected), Red foxes "become very tame, although remaining shy in areas where Beduin eat them". Additionally, just as bold individuals seem better adapted to constant environments, shyer animals appear more flexible in their behaviour, which makes them better able to adapt to a stochastic (variable) environment – rural areas tend to be more stochastic in nature because more pronounced seasonality makes food less predictable. With these contrasting environments in mind, we can now start to see how, over generations, populations evolve to include bolder or shyer individuals.
Anyone with a rudimentary understanding of evolutionary theory will be familiar with the concept of individual variation as a cornerstone to Charles Darwin’s big idea. Generally-speaking, this individuality (be it anatomical, physiological or behavioural) is either beneficial (adaptive), detrimental (maladaptive) or has no impact either way (non-adaptive). In evolutionary terms, it’s the adaptive and maladaptive behaviours we’re interested in here because they make an individual more or less likely to survive and pass on the genes for the behaviour. Suffice to say, if it’s adaptive the behaviour becomes more common in the population, while the opposite is true for maladaptive behaviour. As you’ll probably have spotted, the same behaviour (boldness) can adaptive in one environment (urban areas) and maladaptive in another (rural areas). So, we can see that boldness may be of benefit to an urban fox, but problematic for a rural animal, although this won’t always be the case because deliberate human intervention (e.g. encouraging foxes with food) can change the behaviour of the animal, increasing ‘boldness’. The suggestion is that a fox fed by someone in their garden is likely to associate people in general with food and equally likely to wander up to a stranger looking for a meal. I cannot say for sure that this doesn’t happen, but I personally do not think this gives foxes enough credit. In my experience, foxes learn to ‘trust’ the person putting the food out. Indeed, where I have been lucky enough to observe foxes that are regularly fed, it is interesting that the person putting the food out often notes how the foxes were decidedly more wary when I (a stranger) was there than they normally are. This implies that foxes learn to recognise and trust certain individuals -- something that Oxford University biologist David Macdonald found during his experiments with captive foxes -- rather than assuming every person is the same (and thus a food source).
The universal fox
Recently, the press have carried stories of foxes venturing into people’s houses and biting them, which raises the question of whether simply being bolder means it is also more aggressive? These are invariably serious incidents, although we’re unclear about the exact circumstances, which makes it difficult to form conclusions, and we don’t fully understand what controls boldness and aggression in animals. We do know that areas of the mid-brain respond to hormones (especially testosterone) and certain pheromones cause aggressive behaviour in mammals, while scientists in the USA recently found a protein molecule in the brain of mice (called stathmin) that is crucial for triggering the fear response – when the gene that tells the body how to make the protein was removed, the mice were ‘courageous’. Thus, although there may be cases where boldness and aggression are linked, the data we have thus far suggest these two behaviours are likely to be independently controlled. So, simply that an animal doesn’t run away from you doesn’t make it inherently aggressive and I suspect most of us have experienced this first hand. Whenever I go for a walk in the New Forest I almost invariably meet someone walking a dog; the dog runs up to me to see if I’m someone, or something, interesting. The dog is bold, but shows no signs of aggression towards me. Also, you probably pass hundreds of people everyday on your way to work who don’t run away from you, but that doesn’t mean they’re aggressive people. Similarly, sit on a park bench and eat your sandwiches at lunchtime and you’ll almost certainly be approached by squirrels and/or pigeons; they won’t run away, but they’re exceptionally unlikely to launch an attack on you. This logic follows all the time no attempt is made to interfere with the animal and this is where I think there is potential for problems.
If bolder (or more indifferent) foxes aren’t any more aggressive than shyer foxes, what else could explain the incidents in the media recently? Every year the Fox Project receives photos from members of the public showing ‘their’ foxes asleep on the sofa or in front of the fire, suggesting that in some cases people actively encourage foxes inside. Where an animal is raised by a human, and comes to see them as their guardian/parent, behaviourists call it imprinting. Carers at animal charities tell me that it is not uncommon for people to find what they think an abandoned fox cub and try to raise it – the result is that the animal often imprints on its carer. Under these circumstances, or whenever a fox is repeatedly encouraged to enter a house for food, it may not be surprising for the animal to venture into neighbouring houses, which may then lead to conflict if confronted by the owner. I don’t believe that the fox would mistake somebody else’s house for that of the person initially feeding them, but it seems probable that the animal could learn that houses are a good place to look for food. My experience is that most wildlife is happy to tolerate your presence without any animosity up until you try and initiate contact – that is, until you try to touch or chase it. An increase in boldness, which manifests as foxes allowing people closer to them, has the potential for disaster if those people decide to treat the animal as an extended pet, or behave in a hostile manner. I have said it before on this site and will repeat it here for completeness: foxes are wild animals, not pets. A little commonsense employed when dealing with out wild neighbours, so we treat them as just that -- wild -- will result in far fewer problems.
Thus, in conclusion, we can say that some urban
foxes appear to be getting less concerned at the presence of humans
(often interpreted as being bolder), although this seems to be a
localised phenomenon, rather than applicable to urban foxes in general.
This indifference can make people nervous, but it is important to
realise that it does not mean foxes are more aggressive. The image often
painted by the media is of foxes as the canine equivalent of ‘hoodies’
lurking in alleyways waiting to cause havoc because they can find
nothing better to do with their time. People often believe that the best
way forward is culling foxes, not understanding that this actually makes
the problem worse because the fox population is kept in a state of flux
with a high proportion of young animals in the population. It is
possible to reduce fox numbers with culling, but it is difficult
(especially in urban areas) and very expensive because you have to kill
a lot of foxes, and keep the effort up, to make an impact on numbers.
Instead, the answer is not to encourage animals that you don’t want
around. There are steps you can take to exclude foxes from your
property, although it would take a more cohesive effort from society as
a whole to improve the relationship between foxes and the public. In the
end, a little common sense goes a long way.