The Fox That Would Not Run

AFew wild mammals have settled into cities as completely as the red fox, Vulpes vulpes, and none has been asked to carry so much interpretation. In parts of Britain urban densities now reach about 16 adult foxes per square kilometre, against roughly 1.2 in the farmland that surrounds them, and the animals inside the built-up area differ in more than number. They hold territories a fraction of the size, they are seen more often in daylight, and they let a person come far closer before moving away. What that difference amounts to is the question that organises the field. One account treats the urban fox as a distinct behavioural type, produced by decades of selection favouring individuals bold enough to feed beside people; the other treats it as an ordinary fox reading an unusual set of local conditions, and expects the same animal, moved elsewhere, to behave like any other.

BPetra Lindqvist, who directs the Urban Carnivore Programme at Halden College in Malmö, has spent a decade trying to put a figure on that boldness. Between 2013 and 2021 her group tested 214 collared foxes at baited stations in six cities and in the arable country beyond them, timing how long each animal took to touch an unfamiliar object placed beside the food. The median was 47 seconds for city-born animals and 11 minutes for those born in farmland, and the gap did not narrow when the two groups were compared at the same hour of the night or at the same level of hunger. Her group also measured 168 skulls recovered from road casualties and reported that urban animals had shorter snouts and a braincase on average 3.7 per cent smaller than rural ones, the cluster of changes long associated with domesticated lineages. Lindqvist insists that the skull work describes a correlation and nothing more.

CThe morphology invited a stronger claim, and Lindqvist set out to test it. Thirty-one cubs, born to parents captured either in Malmö or in farmland ninety kilometres away, were reared under identical conditions in outdoor enclosures with minimal human contact and given the same novel-object test. Cubs of urban parentage approached in a mean of 88 seconds against 260 for the others, which she reads as evidence that the difference is at least partly inherited rather than picked up. The effect, however, held only for cubs tested before the age at which wild siblings disperse, about five months; among animals tested after that, the difference between the two lines was too small to measure. Lindqvist states the limit plainly and calls it inconvenient, since the trait she describes as heritable stops being detectable at precisely the age when a wild fox would begin learning the habits of its own street. She maintains that inheritance fixes an animal's starting point and that experience can only move it from there.

DOwen Gallagher, an ecologist at the Institute for Applied Zoology in Leeds, replies that no population can be selected for boldness faster than it can be taught. His survey covered 38 neighbourhoods inside a single city, chosen so that the foxes concerned belonged to one continuous breeding population, which he offers as a way of holding ancestry constant. Where household waste was kept in sealed containers, foxes withdrew when a person came within a median of 28 metres; where residents put food out deliberately, the same measure fell to 6 metres. More telling, he argues, is what followed when one district replaced its bins: over the next fourteen months the distance at which resident foxes withdrew rose from 9 metres to 21, a change occurring within the lifetime of the individual animals under observation. He accepts two weaknesses. The whole survey sits in one city, so it can say nothing about differences between populations, and the withdrawal distances were judged by eye by trained volunteers rather than measured instrumentally.

EThe argument acquired consequences in 2020, when several municipalities rewrote their nuisance-wildlife contracts to fund container redesign and household guidance instead of the removal of individual animals, and complaints naming a particular bold fox began to be answered with a survey of the street rather than a trap. Lindqvist observes, awkwardly for her own position, that an account in which boldness is inherited supplies the cleanest argument for taking the boldest animals out of the population, a measure she has opposed in print for fifteen years and which her results are now quoted to justify. Gallagher answers that the container schemes carry a difficulty of their own: they work only where a whole street complies, and a single household that goes on feeding restores the old distances within weeks. What both dislike is the vocabulary still used in most local reporting, in which a fox that stands its ground is called tame, a word implying an animal permanently altered rather than one behaving as its street allows.

FA settlement is taking shape in which the two accounts are assigned to different circumstances rather than ranked against each other. Where foxes have occupied a city for only a few decades, almost all the boldness on record can be produced by learning, and altering what the streets offer should undo it; where occupation runs much longer and food has been dependable across many generations, a genuine shift in the starting point becomes plausible, and no change of container will reverse it quickly. The measurement neither programme has made is what becomes of city-born foxes that settle in the countryside, whether their descendants revert within a generation or stay unusually bold, and no marked population has been followed long enough to say. Both researchers reject the assumption underneath the popular account, that a fox which approaches people has been tamed by them.