Sometimes we see animals behaving in a way that still defies our full comprehension. Hedgehogs seem to be a particularly good example of this, with the purpose behind self-anointing still largely mysterious. More recently, however, I have observed three activities that I’d not come across before that I think are worthy of mention. The first is a curious “chin wiping” behaviour during which a hedgehog, typically a male going by my observations, rubs its lower jaw along the ground for a short distance, sometimes several times in rapid succession. The other two behaviours appear to be similar in nature and involve, again predominantly males in my experience, wiping or pressing the groin or genitals on the ground.
In March 2020, a hedgehog started visiting our garden that displayed some behaviour I'd not come across before. This individual is a male and highly sexually charged given how he relentlessly circles a couple of the females, fights with other (presumed) males and appears to engage in what appears to be “penis wiping” (see below).
On one of the trailcam videos, while walking around the patio, he would periodically stoop and wipe his chin along the ground. In this first video, the hedgehog did this having just eaten part of a dog biscuit put out on the patio for visiting foxes. In a second one, he did it after having finished drinking from a pot on the patio. Consequently, my initial assumption was that the behaviour was intended to remove crumbs, water or saliva from his mouth as hogs have been observed doing after consuming slugs (i.e., wiping the mucus off their chin). Subsequently, however, he was observed doing this whether he had just eaten or not. Similarly, other hedgehogs drank from the bowl and ate off the patio without rubbing.
The wiping is often preceded by sniffing of the patio first and seems a determined behaviour. Initially, I had considered this may be the hedgehog simply scratching an itch, but it seems quite localised behaviour and (like most hogs) it scratches a lot during its wanderings; I've seen it scratch its chin with its hind foot, which is what I would consider a more typical method of dealing with an itch. He will also go for protracted periods without obviously wiping his chin. He sometimes does this in the presence of a female but equally spent the best part of an hour circling a female on the patio without obviously wiping his chin.
About two weeks after the appearance of the “chin-wiping hog” in the garden, another hedgehog was recorded exhibiting the same behaviour on three occasions during a single night over the Easter bank holiday weekend. The first observation was a brief wipe preceded by a scratch of the face with the right hind foot. The second and third instances involved more prolonged wiping without any associated scratching. In the first two cases the hedgehog was alone, in the third it was joined shortly after by an individual (presumed male) that we had not recorded in the garden before.
One night in early April, there were two courting couples on opposite ends of the patio simultaneously and both males were observed to wipe their chins at least once. Between the first capture in early March and the end of May, we have observed this behaviour 73 times in at least seven different hedgehogs, mostly in males (although these are more frequent visitors) but also in a female who has done it on most nights. Interestingly, the female often appears to angle her head to the (left) side, wiping the side and corner of her mouth/face more than her chin. Similar behaviour was captured by Cambridgeshire-based Hedgehog Champion Carole Barber in May 2020.
Posting the first face-wiping video on social media yielded some interesting responses. Jayne Morgan of the Happy Hedgehog Rescue told me she has seen the behaviour a handful of times in wild and rehabilitated hogs, including one hoglet only a couple of weeks old, while Vale Wildlife Hospital founder Caroline Gould had never witnessed it in the thousands of hedgehogs that have passed through their doors. Veteran hedgehog researcher Nigel Reeve also told me he has never noticed this behaviour and neither, apparently, has Hugh Warwick when approached by Hedgehog Street about it. Six other respondents said they had observed this behaviour in one or more of their visiting hedgehogs, though, and three subsequently provided video clips of the face wiping, which follows the same pattern as that observed in our garden. One of the clips was from Surrey, another from Hampshire and the third from Aberdeen, with the three other reports coming from Berkshire and Norwich. Shortly afterwards, three readers got in touch describing the same behaviour, including one in Cambridgeshire. At the time of writing (October 2020), I've had 20 reports of this behaviour from around the UK.
On first inspection, this behaviour has all the hallmarks of scent marking and it is common to see other mammals (rabbits, squirrels, foxes, etc.) rub their chins on objects to leave their scent behind. While hedgehogs have well developed multi-lobed sebaceous glands in the corners of their mouths, however, they do not, as far as we know, have any specialised submandibular glands that open onto the underside of the chin. That said, in his book Hedgehogs, Nigel Reeve notes that “the hairy part of the skin, the circumanal region and the soles of the feet are well-supplied by sweat glands, creating the potential for the laying of general body-odour trails”; the chin and underside are hairy parts of the skin and, as such, chin wiping could be a method of laying this scent.
Assuming the aim of chin wiping is the application of scent, it is unclear what message is conveyed or the effect such marked areas have on other hedgehogs. I have never observed individuals of either sex pay much attention to 'wiped' areas. The first individual seen doing this appeared to sniff the patio immediately prior to wiping on some (not all) occasions, while the second and third animals were not seen to sniff the ground prior to wiping. Additionally, while scent probably is important to them, we know that hedgehogs are not particularly social and although they're often aggressive towards individuals of the same sex, there is no evidence to suggest they're territorial in the conventional sense (i.e., they don't defend their home ranges from intruders, but rather displace same-sex individuals at concentrated food sources or interlopers during courtship). Consequently, this is not a species we might expect to have evolved an abundance of scent glands, although, as Reeve posits, this does not preclude the possibility of localised use of scent.
In August 2019, there was a thread on this subject on the Hedgehog Street forums and several people reported visiting hogs wiping their chins on their patios. (I presume, as in my case, the fact that they're observed on the patio is largely coincidental, as this is where most people put out food and watch their hogs.) Two observers on this thread commented that they've noted this wiping behaviour either in the presence of a female or having apparently caught the scent of a female that passed by recently. One particularly interesting observation was that the wiping coincided with the presence of a female near a food bowl; the intriguing implication appears to be that the wiping individual may be leaving his 'message' in an area to which he knows females will be attracted.
In our garden it is certainly the case that, when not engaged in courtship, the hedgehogs seem to chin wipe on a particular area of the patio where food (dried dog and cat biscuits) is scattered. Again, the food is placed on a relatively narrow area in order to gain adequate coverage from the trailcams and this probably concentrates activity, which may imply correlation where none exists. Equally, if others are attracted to this area because of the food, this may make it a prime spot to 'leave your calling card', so to speak.
Taken together, these observations suggest that chin wiping is a relatively uncommon, but apparently widely dispersed, hedgehog behaviour. Its purpose remains a mystery at this point. It may be associated with scent marking either around food or in the presence of the opposite sex, possibly both if the context changes according to the presence of either. It may play a role in courtship, males often doing it while circling a sow and, towards the end of the 2020 breeding season, one boar in our garden face wiped frantically while courting a female. It is not obviously associated with agonistic encounters, although in June 2020 Jone Ayres captured footage of a male breaking away from hassling another to face wipe before returning, or specifically with other individuals being present in the vicinity at the time. It doesn't seem seasonal, having observed it from April into late September in our garden, and while remaining a possibility, it seems to me more significant than merely satisfying an itch or clearing the mouth. To this final point, hedgehogs that face-wipe also appear to scratch with their hind feet as is typical of the species and, in our garden at least, they make no attempt to use other objects on the patio (bricks or logs, for example) to scratch against. Hedgehogs have a remarkable ability to contort themselves and I have yet to see a hedgehog fail to reach even the most distant part of their anatomy with their hind foot.
As the 2020 breeding season reached top gear in our south coast garden, two interesting behaviours that seemed broadly sexual in nature were captured on our trailcams.
In the first, the first instance of which was on the 20th March, a large male proceeded to rub his genitals on the patio, including hip-thrusting movements, while sniffing vigorously around a plant pot. No female was obvious in the vicinity and this behaviour, which lasted only a couple of seconds, had all the hallmarks of sexual frustration. Whether the hedgehog obtained any sexual release/gratification from this is unclear, but no ejaculation was apparent, and he didn't press his stomach on the ground during the activity.
The second instance occurred just over six weeks later, on 6th May. This individual briefly thrust his hips, before wiping his face a couple of times and then thrusting for a couple more seconds, rubbing his groin area on the ground and with his penis partially extended. He then sniffed around the patio and left. There was no female obviously in the vicinity, he wasn't observed sniffing unduly at the area he'd just rubbed against and, as with the first instance, there was no evidence of climax. At the time of writing (May 2022), this behaviour has been captured multiple times across the last two years, mostly during the spring. I have so far not observed ejaculation, although I have received reports of what appears to be sperm in and around hedgehog feeders.
The second behaviour was first observed in late April, during a period of about a week when we observed several courtship bouts and mating attempts, two hedgehogs were filmed courting. The male circled the female for a few seconds before stretching himself out on the patio, wriggling and kicking his back legs. He then stood up and carried on trying to win over the female. Two weeks after this incident, a hog was observed backing away from another while doing the characteristic 'bouncing' and huffing of a female warding off an over amorous male. The male paused briefly in front of the female and stretched himself out, pressing his belly to the ground and kicking his back legs, before slowly returning to his feet (hind legs first) and starting to circle her. Considering the penis is located around the midriff in hedgehogs, this behaviour gives the impression the male was pressing his genitals on the ground at the time.
I presume that this is the 'accessory gland marking' behaviour that Walter Poduschka described in his review of insectivore communication, published in 1977. According to Poduschka, males mark the ground, and perhaps the female, with odoriferous secretions exuded from the penis tip through sexual accessory and proctodeal glands. Unfortunately, I've been unable to find any other information on this and it doesn't appear to be a commonly witnessed behaviour.
As well as the possibility that these are the scent marking behaviour Poduschka described, it has also been suggested to me that it might be a form of sexual release, particularly among males who are sexually active before there are many females out and about. Upon raising the point on a Happy Hedgehog Rescue's Facebook page, a lady who has been watching hedgehogs in her garden in west Yorkshire for the last five years got in touch with an account. On one of her hedgehog box cams, she described how:
So far as I can remember he briefly squidged down from his middle, wriggled a little and the noticeable penis swelling was much reduced when he lifted up!”
This report implies that belly pressing/stretching behaviour may sometimes culminate in some form of sexual release. The lady also mentioned that this individual was a large, in her words “randy”, male and he was active earlier than any of the local females.
Finally, it should be noted that I have observed stretching behaviour without any apparent sexual context on one occasion. The hedgehog, which I strongly suspect to have been a female based on a view of its underside in a previous video, was recorded feeding on the patio before stopping to scratch; it then laid on its stomach and stretched its back legs out behind it and front legs slightly sideways, in a swimming-like motion. The stretch lasted only a second and the hedgehog got up and continued foraging. In this case no other hogs were in the immediate vicinity and no wriggling motions were apparent.
At the present time I have too few observations of either the genital wiping or belly pressing behaviour to draw conclusions. Sufficed to say, it doesn't seem unreasonable that hedgehogs may exhibit these behaviours during periods of heightened sexual charge or sexual frustration, as we observe in many other mammal species, or that it is the male's way of letting others know he's around and ready to mate. Alternatively, as I was unable to ascertain whether the two bouts of belly pressing involved the same male, it may simply have been a behavioural 'tick' of one individual. Certainly, given its scarcity in the literature and absence from the many hundreds of courtship videos from our garden over the past seven years, belly pressing does not seem to be a common element of hedgehog breeding behaviour.
I would be very interested to hear from readers who have observed any of these behaviours described above, or have theories to their purpose.