Fantastic Mr Fox – a sequel?

What can USSR genetic experiments tell us about the self-domestication of urban foxes?

My first encounter with a city fox involved hushed tones, tip-toed movements, and wide-eyed awe. Twenty years on, I spot foxes slinking around street corners, hopping over fences, and engaging in ‘who will blink first’ contests. Whilst city foxes possess a wild quality which has withheld them from wide-spread domestication for years, they have become increasingly brazen and bold. Indeed, recent research has shown that there is a possibility that urban foxes are self-domesticating under our noses.

‘A who will blink first contest’
© Phoebe Ashley-Norman

City foxes have been observed since the 1930s; attributable to the expansion of UK cities in the interwar years and increased food sources which encouraged scavenging behaviour. Fox numbers have increased over the years dramatically with a population rise of 30,000 to 150,000 between 1995 and 2017. Attempts to control fox populations by culling have been unsuccessful, resulting in movement of other foxes into unclaimed territories and increased breeding in the following year. Urban fox populations have hence become largely self-regulated.

Foxes tend to dwell under sheds, in tree roots, and even up trees. One particularly resourceful fox, Romeo, broke these conventions and made his home on the 72nd floor of the Shard, when it was under construction. He survived on scraps left by workers before eventually being found and returned to the streets of Bermondsey.

Recent work from Kevin Parsons, an evolutionary biologist at the University of Glasgow, showed signs that urban foxes are becoming increasingly domesticated, despite no active efforts from humans. His evidence for these claims came from comparisons between skulls of foxes from urban versus rural environments. Parsons observed shorter and wider muzzles and a closer resemblance between male and female skulls in urban foxes. These traits were classified by Darwin as examples of ‘domestication syndrome’ and have also been observed in deliberately domesticated foxes.

Morphological differences between urban and rural fox skulls.
© KJ Parsons et al, via The Royal Society Publishing.

One of the only fox domestication attempts was made in 1959 by Dmitry K. Belyaev, and remains ongoing today under Lyudmila Trut, Belyaev’s original research intern. In post-Stalin USSR, where genetic experimentation was effectively banned, Belyaev disguised his research as experiments to improve fur coats.

Belyaev’s study aimed to accelerate the domestication of wild foxes, effectively recapitulating the domestication of other species, such as dogs which occurred between 20,000 and 40,000 years ago. Belyaev began by selectively breeding the most docile foxes he could find. He continued this breeding pattern over subsequent generations, eventually producing the first group of domesticated foxes. In fact, these foxes can be bought today as pets. He used the foxes’ responses to humans opening their cages as a measure of how docile the animals were. The least domesticated foxes cowered from humans or tried to escape the cages, while tamer foxes approached humans and began showing dog-like reactions, like wagging their tails.

The generations of domesticated foxes show a number of notable differences from their wild ancestors. Not only do domesticated foxes have personalities more akin to dogs than foxes: wagging their tails and approaching for food. They also display morphological changes including floppy ears, curved tails, increased markings, and shorter snouts, similar to those observed in Parson’s recent findings. Lastly, domesticated foxes possess altered reproductive habits, becoming sexually mature earlier, having longer breeding seasons and producing larger litters.

Belyaev’s first domesticated fox which exhibited floppy ears. Photo taken in 1969.
© LA Dugatkin via

Although, Belyaev and Trut’s foxes are domesticated in comparison to their wild cousins, they are not tame in the same way that one would consider a dog. Owners have reported furniture damage and finding fox urine in mugs of tea, behaviours which can be eradicated from domestic dogs through training and routine but appear unshakeable in pet foxes. Further to this, foxes are relatively smelly pets, with strong smelling urine, necessary to demark their territory in the wild. It appears foxes still have a way to go when it comes to home manners.

The consistencies between Belyaev’s and Parson’s findings, may reveal self-domestication in the fox population is occurring. Could it be that we will be adopting our back-garden foxes as home pets sometime in the future?