How are animals related to each other in cities while there are no human beings? Thanks to tens of thousands of photographs taken by 150 cameras installed in private gardens in Berlin, a team of scientists has analyzed the ecological relationships between specimens of four species: two wild native, the fox ( Vulpes vulpes ) and the marten ( Tuesday foina ); an invader, the raccoon ( Procyon lotor ); and another, domestic, the cat ( Felis silvestris catus
) . And all this in combination with the disturbance modulated by quarantine and confinement caused by COVID-19. Attention spoiler: cats rule.
Avoid or confront, eat or be eaten, compete, take advantage or cooperate … Wild animal communities are structured around interactions that occur when they share living space. urban environments represent a special case, since human presence and influence often change the rules of the ecological game substantially .
How are wild carnivores related in a city? Has the quarantine affected your behavior? To answer these questions, a team of scientists from the Leibniz Institute for Zoological and Wildlife Research (Leibniz-IZW) installed around 150 cameras in private gardens of different houses in Berlin, With the collaboration and permission of their neighbors, who thus participated in a citizen science project . The objective is to analyze the behavior of foxes, raccoons, marten and cats.
Private gardens, meeting places
The research is part of the citizen project 'Wildlife researchers', led by Stephanie Kramer-Schadt, a scientist at Leibniz-IZW (Germany), and lasted from autumn 2018 until the same 2020 season. The results have just been presented in the journal 'Journal of Animal Ecology'.
The scientists chose the city gardens as a field of study by its ability to attract and drive away wild animals, by acting doubly as a potential source of food and a meeting place, both with humans and animals
The researchers combined the photos recorded by cameras with available information on the size of the gardens, the amount of vegetation, the potential sources of food, the height of the fences and the population density.
In each sample collection period (five different, each lasting one month), the cameras captured around 2,200 and 3,000 cats, out of 300 1,200 common foxes, between 200 and 1,000 raccoons, and 50 to 300 martens. They also captured several photos of other mammals not relevant to the study.
“We were interested in knowing how highly flexible and adaptable carnivore species interact spatially-temporally in human-dominated environments,” explains Julie Louvrier, from the Technical University of Berlin (Germany) and first author of the study. “ We wanted to know if they use the same places and, if so, if they are avoided between species by going at different times of the day or night , for example ”, continues.
More animal activity in autumn
The research group found that the seasons of the year and the quarantine caused by the coronavirus pandemic influence “quite a lot” in the frequency with which the species were recorded . They also found that Fall is a much busier season for foxes, raccoons, marten and cats, unlike spring .
During mobility restrictions, Berliners used their gardens more than usual during the day, which forced the fauna to be more nocturnal. At the same time, the presence of foxes, marten and raccoons in The gardens increased during the confinement periods , “probably due to the lower human presence in the urban space”, the analysts point out.
And, although these species of wild carnivores are somewhat accustomed to the presence of humans, avoid encounters with people , concentrating their movements coughing at night, the period of less activity in the city.
Whenever a greater number of foxes were observed, the same happened with raccoons and martens. And vice versa, since the three species use the same resources of the urban environment. But these species try to avoid each other : there is a delay between the consecutive detections of the different species in the same spaces.
The cat, dominant species
A greater presence of cats meant more detections of raccoons, since they use their presence as a potential indicator of food for leftover cats. Martens and foxes, on the other hand, did not appear more frequently when there were cats, which, according to the scientists, indicates “a hierarchy of the four species, among which the cat is the dominant ”.
This statement was corroborated by another surprising conclusion of the study: Cats do not avoid other animals, whatever the time of day , although their body mass – considered an indicator dominance in the wild – is normally less than that of foxes and raccoons.
“We humans modify the behavior and way of life of wild species. The quarantine was a blessing, as it provided an opportunity to study what our wild neighbors do when people suddenly disappear from urban space, ”emphasizes Kramer-Schadt. It was important because human pressure causes an “exacerbated effect” on community dynamics .
” Our research sheds some light on the rules that govern interactions in a community of medium-sized carnivores living in an urban setting, ”concludes Louvrier. Something has become clear: domestic animals exercise their dominance over local fauna , even on species that are relatively well adapted urban environment.