Urban environments present unique challenges for wildlife, especially highly mobile and adaptable species like red foxes (Vulpes vulpes). In a recent study published in Molecular Ecology, researchers from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) and the Luxembourg National Museum of Natural History (NMNH) explored how physical and behavioral barriers shape the movement and genetic structure of red foxes in Berlin and surrounding rural areas.
Foxes in the City: Genetic Clustering and Barriers
Red foxes are known for their remarkable adaptability, thriving in cities like Berlin since the 1950s, with their population spreading across the city by the 1990s. However, the researchers uncovered a surprising divide: despite their mobility, there are two genetically distinct fox populations—urban and rural—living side by side but rarely mixing.
The team collected genetic data from over 370 foxes in Berlin and the surrounding rural region of Brandenburg, using 16 microsatellite loci to study their genetic structure and dispersal patterns. They found that while foxes in rural and urban areas live in close proximity, they remain genetically separate.
Physical and Behavioral Barriers
Interestingly, physical barriers such as rivers and man-made structures like motorways and railways did limit some movement between urban and rural foxes, but these alone did not fully explain why the populations stayed distinct. Instead, human activity and the foxes' behavioral responses to it played a much larger role in shaping their dispersal patterns.
Human Activity as a Key Barrier
The research revealed that rural foxes are more cautious and avoid areas with high human activity. They are reluctant to cross into urban environments, which are often bustling with people and dense housing. On the other hand, urban foxes have developed bolder behaviors that help them navigate city life. However, they still prefer to use infrastructure like motorways and railways, where there is less pedestrian activity, rather than taking safer but busier routes like public streets.
This risk-averse behavior of both populations creates a divide, with rural foxes rarely venturing into the city and urban foxes finding specific, low-traffic corridors to move within the city. This has led the researchers to describe the city of Berlin as an "urban island" for foxes, where behavioral differences rather than just physical barriers keep the two populations apart.
Evolutionary Pressures and Adaptation
One reason for the behavioral differences between urban and rural foxes could be human hunting pressures. Fox hunting is still practiced in many countries, creating evolutionary pressure for foxes to avoid humans and their activity centers. This selection pressure may explain why rural foxes stay away from cities, even when food resources are more abundant there. Urban foxes, however, have adapted to coexist with humans, but their preference for moving along potentially dangerous routes like motorways shows they are still wary of direct human contact.
Understanding Urban Wildlife
This study highlights the importance of considering not only physical barriers but also behavioral factors when studying urban wildlife. In the case of Berlin's red foxes, the combination of human-made structures and the foxes' responses to human activity has created distinct urban and rural populations. As cities continue to expand, understanding these dynamics is essential for predicting how other wildlife species will adapt to urban environments.
By examining how red foxes navigate the urban-rural landscape, the researchers provide valuable insights into the complex ways animals adapt to human-dominated environments. These findings not only shed light on fox behavior but also open up new avenues for studying how other species may respond to the challenges of urbanization.
Sources:
