Tackling any of the six species of deer found wild in the UK is well beyond the capability of a fox, but dietary studies do occasionally find venison remains in fox scat and stomach contents. Invariably most of these remains originate from carcasses that the fox has stumbled across and in some northern habitats such carcasses can be an important component of the fox’s winter diet. In some cases, however, the remains may be of yearling deer – called a calf, fawn or kid, depending upon the species. How significant foxes are as a predator of deer calves is unknown for most species, but they are thought to be significant predators of Reeves' muntjac (Muntiacus reevesi) (see: The Fox as an Ally) and Chinese water deer (Hydropotes inermis) fawns. It is their relationship with roe deer (Capreolus capreolus) has been studied most extensively, though.
In 1972, Helmuth Strandgaard presented data on a population of roe deer at Kalø in Denmark; they show that, when fox control in the area ceased, the number of Roe deer kids surviving dropped by 60%. Similarly, during a two-year study of roe mortality in Sweden, Ronny Aanes and Reidar Andersen found that fox predation was the biggest cause of kid death. More recently, in 2004, Swedish University of Agricultural Sciences biologist Anders Jarnemo completed his doctoral thesis on neonatal mortality in roe deer – i.e. how many, and by what means, new-born roe kids died. Using data collected in two areas of central Sweden between 1986 and 2003, Jarnemo found that about half of roe kids died during the summer months and foxes were responsible for the majority (88%). The kids were most vulnerable to foxes during their first week of life, the threat decreasing with increasing age. Most (85%) kids were taken before they reached a month old, with only 2% of those taken being older than 40 days.
In one of the areas, Jarnemo found that fox abundance was the only factor that had a significant impact on kid survival in any given year (i.e. more kids survived in years when fox abundance was low, such as during a serious outbreak of mange) and, in both areas, kids born early or late in the season were most at risk from fox predation. Jarnemo also found that does (females) were more likely to lose a kid left hiding in open habitats, where they were presumably more visible to foxes, although they were quite capable of chasing away a fox if they spotted it. Indeed, in his book The White Foxes of Gorfenletch, Northumberland naturalist Henry Tegner recounts watching a vixen kill a roe deer kid before being driven off by its mother:
“When [the kid] was within five feet of the vixen she sprang for his throat. Like a terrier, the vixen shook the little roe to break his neck.”
The kid's short cry brought the doe down the knoll at full charge and:
“Seeing the vixen, [the doe] went straight for her, her front hooves striking out at the fox like a pair of stabbing lances. Leaving the dead fawn where she had killed him, the yellow vixen beat a tactical retreat.”
Tegner recalls that the doe stayed with her dead kid and its sibling until dusk, when she and her remaining kid moved off to feed. With the coming darkness the vixen returned, collected the dead kid and carried it back to her cubs. I have included Tegner’s account here because, although I suspect some of the story as told in his book is embellished with artistic licence, he was a well-respected naturalist and member of the British Deer Society. As such, I believe his observation to be broadly accurate about how a mother deer would attack a fox. It certainly ties in with other accounts I have come across.
So, overall, foxes can have a significant impact on roe deer kid survival, although it is important to consider the habitat, birthing period, mother and kid behaviour and, presumably, the availability of other food sources.
One final point on the interaction between deer and foxes: not all encounters are aggressive or predatory. I have seen foxes cross through fields of deer with each ignoring the other and, in the New Forest, have watched a fox pouncing on rodents in a field as red and roe deer grazed, their young hidden nearby. There is also an interesting, but unconfirmed, report of apparent play behaviour between a muntjac and fox. (I remain sceptical having not seen the video, but the reference is included here for completeness.) In May 2008 a gentleman posted on a wildlife Internet message board describing footage that he had been sent by a friend showing a fox and Reeves' muntjac deer in the garden of their London home. He explained:
“[the footage] is of an adult fox and a muntjac deer playing wildly together in the garden. They take it in turns to chase each other around the various shrubs etc. The fox looks the most enthusiastic of the two, cavorting and leaping around like a big kitten with those characteristic 'mouse jumps'.”
One forum member responded to say:
“It's been seen before at Thames Valley Park by their night security officers, but so rarely you'd have to be very, very lucky to catch it on film”.
A quick Internet search revealed that Dave Coward has some clips of a muntjac and fox interacting in his garden on his YouTube channel, but I would caution against interpreting this as anything more than curiosity on the part of both species. I would be very interested to hear from readers who have witnessed any similar behaviour.