October 20, 2021

I, Science

The science magazine of Imperial College

Family feuds, gang wars and illicit affairs – the urban fox might only live for a maximum of five years but they pack a lot in.

We tend to only see only one fox at a time, normally a streak of light brown across an empty street. But London’s foxes live in extended family groups and, although they hunt alone, each territory can be shared by up to 10 adults.

Within the group there is a strict dominance hierarchy that rules much of their lives. Usually it is only the dominant vixen that has cubs. She will sometimes tolerate other litters and these “extra” cubs can even be reared with her own. At less convenient times, however, she will kill them.

Stuck in the breeding earth for several weeks it is other members of the group that bring the vixen food. Male foxes are renowned for being “devoted fathers” and they are, if a little misguided.  Foxes have such complicated sex lives that it is difficult for a dog fox to know which of the cubs are his. As a result all of the group’s males act as if they’re the father, helping to guard and provision the cubs as if they were all their own.

Some of her cubs are usually sired by the alpha male who, although he also mates with subordinate females, focuses his attentions on the dominant vixen. When it comes to outside the social circle, however, any fox is fair game regardless of rank. In fact most of the cubs in a litter will be sired by dog foxes from neighbouring families. It’s easy to know when a vixen is on the prowl for neighbouring mates.  That harsh unearthly scream you sometimes hear in the dead of night? If it happens in winter, it’s probably a vixen calling out for her neighbours.

At the moment we are in the middle of baby season. Mid-March is when most cubs are born, although it’ll be another four weeks before they see the light of day. Things aren’t all cosy for the cubs however – 20% of them die underground. One of the reasons is that dominance begins to be fought over in the den.  It is dominant cubs that are given more food, grow faster and are more likely stay in the social group once they’ve reached adulthood. The “play fights” can therefore be vicious and some cubs get killed in them. Once everyone has learnt their place things tend to calm down and although the foxes may meet for only a few minutes in a day, strong social bonds form between group members.

Each gang defends a territory typically extending across 80 of our gardens and scent-marking happens every night to warn off rival groups. London is split into fox sized territories, not only do our sheds make good dens but our streets make the perfect highways, even our busiest roads are used to delineate between territories. There is a parallel world right on our doorstep and in the midst of our humanity is another species busily making the city their own.