Squirrels face various challenges in the city – including us humans, but also predators such as cats, dogs, martens and birds of prey. In a citizen science project in Berlin, biologists examined in more detail how the squirrels adapt their behavior to these circumstances. It turned out that the urban squirrels are good at assessing when and from whom there is a danger.
In Europe, the Eurasian squirrel (Sciurus vulgaris) is the most common representative of the squirrels. Originally adapted to life in the forest and other natural environments, the climbing rodent with reddish fur has long since conquered our cities as a habitat. Allotments, backyards and parks offer it food and living space. But in this human-dominated environment, the squirrels not only encounter other wild animals, but also domestic animals such as dogs and cats and, of course, people. How much does this affect rodent behavior?
Flexible adaptation to different predators
To investigate the adaptation of urban squirrels to their environment and its pitfalls, Sinah Drenske from the Leibniz Institute for Zoo and Wildlife Research and her colleagues in Berlin started a citizen science project. To do this, volunteers set up wildlife cameras in their gardens in the spring and fall of 2019 and 2020. The researchers then evaluated the images from the cameras, focusing on the seasonal and daily activity patterns of the squirrels in the various urban contexts as well as the animals’ reactions to the presence of people, cats, dogs and predators such as stone martens. The wildlife cameras took a total of 1,335 images of squirrels, 14,087 of cats and 715 of martens during the observation periods.
The results confirmed that the squirrels adapt very flexibly to the presence of potential predators: “Our study shows that squirrels primarily change their behavior to avoid predators and not people,” says co-author Stephanie Kramer-Schadt from Leibniz -IZW. The squirrels therefore avoided places and times where martens, cats, birds of prey, etc. were present. As soon as the danger passed, the squirrels quickly reappeared. “When there were no predators in the images, we saw an increase in their activity and the squirrels used the time to look for food on the ground.”
Cats worse than martens or dogs
The researchers found that who squirrels seem to fear most is cats. “The constant presence of cats forces squirrels to be constantly vigilant and constantly adapt,” explains Drenske. “In contrast, with beech martens – whose presence is rare during the day and mainly limited to the night – squirrels can revert to their normal behavior when they are no longer present.” A perhaps surprising result of the study: Dogs, on the other hand, don’t seem to bother the squirrels too much. “Our hourly and seasonal analyzes showed no significant influence of dogs on the behavior of squirrels,” reports Drenske.
The corona lockdown during the observation period in 2020 also influenced the activity of the agile animals. “We were able to prove that squirrel activity in gardens increased during the Covid lockdowns,” explains Drenske. The researchers explain this by saying that as people spent more time at home, they set up more feeding stations for squirrels and birds. “The additional food sources may have encouraged squirrels to be more likely to visit gardens with feeders,” Drenske continued. A wildlife-friendly garden therefore contributes to the well-being of wild animals in the city.
Source: Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW); Specialist article: Frontiers in Ecology and Evolution, doi: 10.3389/fevo.2024.1455142