Many people have suggested that we now live in an age of Earth’s history known as the “Anthropocene”, where humans have a large impact on the Earth’s shape and ecosystems. The biggest piece of evidence for this is the human impact on climate change, which is resulting in ecological changes across the globe. However, the impacts of human activity can alter Nature on a smaller scale too. This study from June 2020 investigates how urbanisation in London has resulted in two separate fox populations with differently shaped skulls. Urban fox skulls are shown to have shorter wider snouts and a smaller braincase compared to their rural counterparts.
These differences were discovered through a great deal of mathematics and statistics on the skulls of 111 red foxes, which were kept in the collections of National Museums Scotland, that originated from London and surrounding boroughs. Some of the skulls were over 50 years old, so their location of origin had to be compared with old maps to determine if the area was urban at the time of the fox’s life.
Two theories are put forward to explain why these two fox populations, one rural and one urban, may have begun to evolve differences in skull shape (skull morphology). The first theory is that due to differences in diet, the fox’s skulls may benefit from a different shape to tackle their food. It is said in the paper that 37% of an urban fox’s diet may be scavenged human food. This means that rather than hunting food as would be typical of a rural fox, often they will have to access food through various packaging or containers. I know I have had my fair share of bins torn open by a fox looking for a snack! The shorter wider jaw has a slower shutting speed, but a stronger biting force. In contrast, a rural fox may have to catch a fast-moving mouse or rabbit. Here a faster jaw would be beneficial for hunting, which can be found in a longer thinner jaw.
Another theory is that urban foxes are experiencing what is known as “domestication syndrome”. Domestic dogs have been very well studied and are descended from wolves. Wolves are very social animals that can convey and interpret facial expressions in packs. Domestic dogs are thought to have evolved shorter, wider skulls to have facial expressions that are more interpretable by the humans that they were in contact with. Perhaps the same is occurring to urban foxes? Then again, dogs have been specifically bred by humans for thousands of years, so it is hard to assume this for certain.
So, while we may not be able to figure out why urbanisation may be having these effects on foxes it is certainly interesting to see the influence that human activity can have on the natural world on a smaller, less obvious scale.
The original paper can be found here.