Despite some valid complaints, foxes do have their benefits. Even to the exclusion of the joy many people get from interacting with them, foxes provide vermin control (preying on mice, rats and pigeons) and run a litter clean-up service in urban areas by eating discarded food. In rural areas, foxes feed heavily on rodents and rabbits that can be considerable pests to farmers.
In a paper to the European Journal of Wildlife Research published during 2011, for example, Bryony Tolhurst at Sussex University and her colleagues presented their findings on foxes visiting farm buildings. Tolhurst and her colleagues analysed video and still footage from 422 separate visits and observed that the foxes rarely ate the animal feed (although they frequently scent-marked it); instead the biologists noted frequent pouncing behaviour, suggesting that the foxes were visiting the buildings to hunt rodents. Scottish naturalist James Lockie estimated that a fox could eat at least a thousand voles each winter, saving the famer a potential 10.5kg (23 lbs) of grass (i.e. sheep/cattle food).
It is very unlikely that foxes could actually control the populations of either rodents or rabbits in rural Britain, but they do represent a significant source of mortality for both groups. In their contribution to the 2003 compendium, Conservation and Conflict: Mammals and Farming in Britain, David Macdonald and his co-workers (including Jonathan Reynolds from the GWCT) used the 1997 grain price to calculate, all other inputs ignored, that a farmer about to shoot a young fox, newly recruited into the rabbit-eating population, could forfeit between £156 (in 1997, about 250 USD or 225 EUR) and almost £900 (almost 1,500 USD or 1,300 EUR) in saved grazing – in other words, depending on the population density of rabbits, the number of rabbits the fox could take could eat some £900 worth of the farmer’s crop. Overall, the biologist concluded:
“If we apply the calculations presented above and ignore other inputs, total national annual saving of approximately £30-£150 million [49-246 million USD or 43-216 million EUR in 1997] worth of crops thanks to foxes killing rabbits would be suggested.”
Obviously, these are calculations based on a whole host of variable factors, and it is a complex task to weigh up economic benefits of culling one species to protect another. What these figures do, nonetheless, is suggest that foxes have the potential to be beneficial to farmers as a form of pest control.
More recently, evidence has come to light suggesting that foxes may have a role to play reducing the incidence of Lyme disease. This is not a particularly new idea and back in 2012 Oregon-based wildlife ecologist Taal Levi and colleagues published a paper in the Proceedings of the National Academy of Science suggesting that, areas where coyotes suppress the abundance of red foxes also have a higher incidence of Lyme disease. The theory goes that foxes reduce the number of small mammals that typically provide the first host for tick nymph – fewer rodents, fewer potential meals for tick nymphs, fewer adult ticks to potentially carry infection.
Levi’s conclusions were questioned in a subsequent review, but in a 2017 paper to the Proceedings of the Royal Society B Tim Hofmeester and co-workers presented data supporting the idea. Hofmeester and his team studied tick burden among rodents from 19 forest areas in the Netherlands with varying levels of predator abundance and found that bank voles and wood mice in plots with higher predator activity had lower tick burdens than those in plots with little predator activity. They researchers concluded:
“The results suggest that predators can indeed lower the number of ticks feeding on reservoir-competent hosts, which implies that changes in predator abundance may have cascading effects on tick-borne disease risk.”
Finally, there are some preliminary data implying that foxes may have an impact on some larger pest species – specifically the Reeves' muntjac (Muntiacus reevesi). The Reeves', or Chinese, muntjac is a small oriental deer that was introduced to Britain during the late 19th or early 20th century and, from only a handful of females, has now colonised much of England. Despite some benefits when deer are present in forests at low densities, muntjac are widely considered a pest species capable of inflicting significant ecological damage in woodlands. Consequently, it is seen as an invasive species and a great deal of time and money has been invested trying to eradicate it; largely unsuccessfully, it has to be said.
Part of the key to the muntjac's rapid colonisation lies in their phenomenal breeding potential. Unlike all other species of deer in Britain, muntjac do not have a breeding season. They can produce young throughout the year and females will spend virtually their entire lives pregnant. They can also be pregnant while still suckling their previous fawn. Furthermore, the fawns are tiny (newborn about the size of a kitten) and not easy to locate. This, coupled with the small stature and secretive habits of the adults, means that populations are often well established before they make their presence known. Research by Cambridgeshire-based deer biologist Arnold Cooke suggests, however, that foxes may have a limiting impact on some muntjac populations through their predation on fawns.
In an intriguing article to the journal Deer in 2014, Cooke presented some data on estimated abundance of foxes and muntjac in Monks Wood and at Holme and Woodwalton Fens. In particularly, he described how the muntjac population of Monks Wood boomed during the late 1980s and early 90s when the fox population was very low – even the carcasses of long-dead deer were seemingly unscavenged by foxes. Similarly, there was a period between 1996 and 2005 when foxes were comparatively rare at Holme Fen; the frequency of muntjac sightings doubled there between 1996 and 1998, remaining high until stalking began in 2005. Unfortunately, there are other factors that complicate direct comparisons of fox abundance with deer sightings, but, overall, Cooke’s observations suggest foxes may affect muntjac population dynamics by preying on fawns, which may in turn slow colonisation, restrict density and aid management. In his article, Cooke notes:
“My work has shown that a flourishing fox population may be a management benefit in nature reserves where muntjac are, or could be, a problem to conservation interests. Other people, who are controlling both muntjac and foxes, might like to consider how they can manage the balance between these two species for maximum effect.”
Circumstantial evidence from deer managers supports Cooke's observations. Several stalkers and gamekeepers have told me that muntjac numbers increase almost to the point of being a nuisance when they work to significantly suppress the local fox population (“hammer foxes”, as one gamekeeper put it). Given that these species don't directly compete for resources, annectodally this implies population suppression through predation.