Human activity is transforming the environment so much that many animal species are losing their place to live. But there are also a minority of species that can adapt to the new reality to some extent, or even prosper in it. Although life in the city means noise, pollution and less vegetation, there are also positive sides: an additional source of food all year round (in the form of leftovers from our tables) and fewer natural enemies (although cats are a big threat for many birds).
Living around people has an impact on animal behavior – for example, many birds in cities sing at higher frequencies to distinguish themselves from traffic. Research on birds also indicates that those living in urban areas are better problem solvers.
Coping with new problems seems to be one of the most important cognitive skills needed in the rapidly changing and unnatural environment created by humans. Recently, scientists have shown that mice that live close to humans are better problem solvers and, in at least one species, this is an innate ability that is a result of evolution, instead of something they learned during life.
Urban versus rural mice
In the first experiment, scientists caught striped field mice in the city and in rural areas. After treating all mice the same for a year in the laboratory, the tests began.
The mice were given various problem-solving set-ups (including a LEGO house – I’m not the only one who comes up with such ideas) which when opened – by pulling, pushing or moving various elements – gave them access to food.
Mice that were caught in the city were more likely to solve these problems. This couldn’t be explained by a fear of strange objects in the rural mice, because they actually approached the set-ups sooner and interacted with them longer.
As I wrote above, this experiment was carried out on mice that were born and grew up in the wild and it is possible that they could develop their cognitive abilities then – differently in rural and urban areas.
Long-term coexistence with humans
To find out the importance of long-term coexistence with humans, the same scientists conducted research on another species of mice – the house mouse. It is a synanthropic species that occurs almost exclusively near humans (this species also includes laboratory mice and various breeds of domestic pets).
There are several subspecies of domestic mice that have been associated with humans for different lengths of time: the Western European house mouse (Mus musculus domesticus) – about 11-13 thousand years, the Eastern European house mouse (Mus musculus musculus) – about 8,000 years, and the southeastern Asian house mouse (Mus musculus castaneus) – between 7,600 and 3,800 years. Thus, each of these subspecies had more or less time to adapt, through evolution, to humans’ changes to the environment (even if the living environment of people also changed a lot over these thousands of years). To eliminate the influence of individual mice’s life experience on the research, scientists did not study wild mice caught in the field, but studied their descendants, after several generations in the laboratory under constant conditions.
Adapting to life with humans
The descendants of the wild house mice were subjected to the same problem-solving tests as the field mice in the previous experiment. It turned out that the longer a mouse subspecies was associated with humans, the more likely it was to solve the problems. And this couldn’t be explained by the differences between subspecies in the time they took to approach the set-ups, or the differences in fear of a new environment.
Since all these experimental animals had lived under the same conditions throughout their lives, these studies show that different subspecies differ in their innate ability to deal with new problems. It seems that over the course of generations, coexistence with humans influenced the evolution of cognitive skills in wild animals.
Photo based on 4028mdk09, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=11056096
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