Urban red foxes are becoming more similar to domesticated dogs as they adapt to their city environment, according to a new analysis.
"A team led by Dr Kevin Parsons, of the University of Glasgow’s Institute of Biodiversity, Animal Health and Comparative Medicine, has carried out an analysis into the differences between urban and rural red foxes in the UK.
Their findings go some way to explaining how dogs could have evolved into our current pets.
With our current lockdown measures due to the covid-19 pandemic we are seeing a number of animals more frequently in our cities. It has been known for some time that cities create new habitats for wild populations. While many can’t cope, it is recognised that some types of animals are especially good at living within cities. Red foxes are prevalent within several cities within the UK and elsewhere where they have become well-established.
“We wondered whether this change in lifestyle was related to adaptive differences between urban and rural populations of red foxes. We assessed skulls from hundreds of foxes found within London and the surrounding countryside and saw that urban foxes had a smaller brain size capacity but also a different snout shape that would help them forage within urban habitats. There was also less of a difference between males and females in urban foxes,” said Dr Parsons.
These changes matched up with what would be expected during a domestication process. In other words, while urban foxes are certainly not domesticated, they are changing in ways that move them closer to what is seen in many domesticated animals.
“This is important because human-animal interactions are continuous and some of the basic environmental aspects that may have occurred during the initial phases of domestication for our current pets, like dogs and cats, were probably similar to the conditions in which our urban foxes and other urban animals are living today. So, adapting to life around humans actually primes some animals for domestication, added study co-author Dr. Andrew Kitchener from National Museums Scotland.
The researchers from the Universities of Bristol, Edinburgh and Massachusetts and National Museums Scotland, then decided to test whether differences found between urban and rural red foxes had any similarity to what is found across different species of foxes.
“This could tell us whether the evolution of urban/rural differences was completely unique or something that has potentially happened previously. It turned out that the way urban and rural foxes differed matched up with a pattern of fox evolution that has occurred over millions of years between species. While the amount of change isn’t as big, this showed that this recent evolutionary change in foxes is dependent upon deep- seated tendencies for how foxes can change. In other words, these changes were not caused by random mutations having random effects the way many might think evolution occurs,” said Dr Parsons.
The team’s research paper, Skull morphology diverges between urban and rural populations of red foxes mirroring patterns of domestication and macroevolution, is published in the Proceedings of the Royal Society Series B."
Hypothesis questioned in North America
"As foxes move from the forest to the city, they show more doglike traits and appear to be naturally self-domesticating in the U.K. — but the same isn’t happening here at home...
Foxes in Canada are not showing domestication syndrome like U.K. foxes are, and Parsons says there could be many reasons to explain why this is the case including that the foxes in Canada and the U.K. come from a different lineage and may not evolve the same way.
Population density may also play a role: Toronto has a lot of open space compared to Glasgow, meaning foxes can be timid and find hiding places more easily in a Canadian city. The cities in the U.K. also have more of an abrupt end compared to Canada, he adds.
“In Canada, you drive an hour and it’s sprawled out with suburbs. So, getting access to the centre of the city takes much longer,” he says. “Here, I live in the suburbs but in five minutes I’m in the core of Glasgow. Then, a five minute drive the other way takes me into cow fields and countryside.”
There’s no study that looks at domestication syndrome in Canadian foxes, at least to Danielle Fraser’s knowledge.
“Something I thought would be an interesting extension to this study is looking at populations from other urban and rural pairs throughout the range of modern foxes,” says Fraser, an evolutionary biologist and research scientist at the Canadian Museum of Nature.
Pointing to how the snouts of urban foxes got shorter in the study, Fraser adds that previous studies have shown canines being more prone to evolvability in the face, particularly the snout, than other parts of their skull. "
© Nicole Watson/Can Geo Photo Club
More information on foxes and skull changes due to domestication, see also;
"Researchers have discovered that what makes for a beautiful face in a fox, is similar to the features of an attractive human. The study found that features seen in farmed foxes - such as flat faces and smaller jaws, as well as a large space between the height of the cranium and face - are the same features that humans find desirable. According to Dr Elia, the link is hormonal and estradiol and serotonin, which regulate behaviour, also dictate some aspects of development"
I think that one reason they have not seen the same in North America is because a high percentage of North American red foxes are lineages of feral farmed foxes, which may already possess these adapted traits prior to feralization. The native species of fox are so few in number, one subspecies is now listed as endangered. They also do not have the density of foxes and humans per square mile as we do, where habituation over generations is more likely.
I also think it is possible, in London and Halifax especially, that feral farm foxes may have contributed to fox population genetics and that it might also be one reason we are seeing such traits - on top of the consistent generational habituation, as London was the fur capital of the world at one point, with several fox farms and furriers listed as being in the city pre world war II (when rationing and fox farmers being called up for service saw the release of stock into the countryside). Another indicator of this possibility is the high rate of melanism in both London and Halifax fox populations.