The Town Mouse and the Country Mouse: Urbanisation and Evolution

Studies on the behaviour and evolution of different species, both historically and in the present, has led to fascinating conclusions about how urbanisation and globalisation have impacted the animal kingdom. Phenomena such as man-made migration, changing patterns of behaviour, changing physical features, and even speciation shed light on life in these artificial ecosystems.

The first thing to note is that due to human immigration, cities have brought together species not native to that land, collected from various backgrounds. This has occurred both accidentally and deliberately, as in the case of the parakeet population of Belgium which descends from one group of birds released in 1974 by the owner of a zoo who thought they would brighten up the city of Brussels. These foreign species are fed by a variety of plants, also originating from around the globe, which we grow in our gardens and on our streets.

This is only the tip of the iceberg, however. Our urban species have started to adapt their way of life to the environments they species find themselves in, one example being the UK tits with the surprising ability to open all manner of milk bottle tops. In some cases, the pressures of urban life have been sufficient to trigger the evolution of the species. It was found, for example, that American cliff swallows, which are often found on bridges and roads, had undergone a decrease in wingspan. Correspondingly, individual birds found dead on the road had a higher than average wingspan. The conclusion was drawn that only birds with wings short enough to fly up vertically from the road were able to dodge traffic and reproduce, thus propagating the short wing gene.

An even more interesting observation for researchers has been the signs of speciation, the process by which evolution forms multiple distinct species. One example of this is the blackbird, originally a forest-dwelling animal which is now a common sight in cities. Research from blackbird populations of various countries indicates that the urban blackbird is on the cusp of developing into a distinct species, due to the evolutionary influences of their particular environment.

Applicants for Biology, Natural Sciences, or Geography and those interested in environmental issues may wish to familiarise themselves with the phenomena observed among species in urban environments, and should think more generally about the impact of human lifestyles on other species.