Helen Whiteside, 9th November 2010
Life in an Urban Fox Family
Helen is researching urban foxes at the University of Bristol as a member of a project which has been under way for over thirty years. She presented an absorbing account of general fox ecology and gave us an insight into some of the latest research findings.
There are several species of fox and we had a quick look at three of them: the Arctic, the Bat-eared and the Cape foxes, before homing in on the one with which we are familiar - the red fox. The red fox and its variant the silver fox is distributed throughout the northern hemisphere. It has also been introduced to Australia where it has become a significant pest.
The urban fox is, of course, the same species as the rural one, the difference being that it has adapted wonderfully to life in the big city. One has even been seen taking a ride on a London Underground escalator!
Like its country cousin, the urban fox establishes a territory occupied by a dog fox, a vixen and their cubs, the difference being that the urban territory is usually much smaller, given the greater availability of food. Their breeding behaviour is familiar at least in part to many people. Mating takes place in January/February with the female being receptive for four days. Most people will have heard the eerie screams coming from a pair of mating foxes but not everybody will have witnessed the phenomenon of "post-copulative lock", which prevents them from separating and may last for some time.
Pregnancy normally lasts for 53 days and the cubs are born at the end of March/beginning of April. A den is prepared for the young, often in a nice cosy location such as under the floorboards of a shed or, even better, a house. The cubs are usually around six in number, and appealingly mischievous and playful. By the age of 18 weeks they are feeding themselves, rats being a favourite item on the diet.
Once raised to young adulthood the cubs disperse and new territories are taken up in time for the next breeding season. The process by which this occurs is complex, and still very much subject to investigation. Observations include the fact that females don't travel as far from their parent's home territories as the males. Sometimes a territory may be taken over from a fox that has died or alternatively a new territory may be established between existing ones. Helen herself is carrying out her PhD research into the question of whether the young foxes disperse of their own accord or whether they are effectively "kicked out" by their parents.
The main causes of death among foxes appear to be road accidents and the very unpleasant disease of mange. This is related to the human disease of scabies and is transmitted by mites. Many people will have seen the distressing sight of a fox that has lost large amounts of fur and is obviously in a highly debilitated condition. In 1994-1996 there was a major outbreak of mange in Bristol which led to a massive crash in population. The same thing has been experienced in other populations of urban fox.
Foxes sense the world around them in a somewhat different way to humans. Although their sight is good they detect movement differently. As a result it is possible to be approached quite closely by a fox as long as you don't move. Their hearing is very acute and aided by ears which can be moved independently, a feature which is put to good use in locating prey.
Rather like squirrels, foxes are "programmed" to exploit gluts and cache food away to be consumed at a later date. This was offered as an explanation for the slaughter that takes place when a fox gets into a chicken coop, and the way the contents of dustbins get strewn about.
The Bristol University research project began in 1977, initially because of concerns about the risk of rabies. The Bristol population has not changed greatly in the last decade and is thought have reached a stable level, though it is still susceptible to crashes brought about by epidemics of mange. It is not considered possible to limit the population artificially as this would require numbers to be reduced by 70 per cent every year. It was tried unsuccessfully in London in the 1970s and abandoned as a strategy. In Australia, where the fox is an alien species, it has reached pest proportions and no solution to its control has yet been found.
The Bristol researchers make use of coloured ear tags and radio collars to detect the movements and dispersal patterns of their subjects. Public cooperation is important both in reporting sightings and in the placing of traps.
Urban foxes are studied worldwide and Helen concluded by describing a fascinating project that had been carried out in Russia. In an attempt to understand the process of domestication, silver foxes had been selectively bred for tameness. In ten generations they had effectively produced a creature more akin to a dog, complete with droopy ears and larger eyes and altogether "cuter".
For more information Helen recommends:
Urban foxes by Stephen Harris and Phil Baker (British Natural History Series) published by Whittet Books.
For online information about Helen's Department, google Bristol University Mammal Research Unit or go straight to: