Impact of urbanization and anthropogenic food sources on the ecology and energy budgeting of the Eurasian red squirrel (Sciurus vulgaris)

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The goal of this study is to understand and quantify the impact of urbanization and anthropogenic food resources on the ecology and energy budgets of small synurbic mammals, which occur in higher densities in urban than natural habitats. Furthermore, we aim to determine whether these high population densities indicate that a species is thriving, or if the habitat is acting as an ecological trap containing inbred individuals. Therefore, we will contrast various ecological traits and the genetic diversity of populations of the Eurasian red squirrel (Sciurus vulgaris) inhabiting small patches of urban habitat with those living in natural areas. As high food availability seems to contribute to increased urban densities, we will investigate the influence of the abundance of natural and supplemented food resources. We expect that the latter is of high importance for urban wildlife and by conducting a citizen survey we will be able to quantify these food sources and their spatial and temporal distribution. We predict that squirrels in urban sites will have a stable body mass and condition throughout the year, even during the seasons of food scarcity (i.e. spring and summer), owing to high amounts of supplemented food. This will likely be in combination with more numerous reproductive individuals. However, it is plausible that we will also detect negative effects of urban inhabitation such as malnutrition, caused by an unbalanced diet, or high parasite loads, resulting from high inter-individual contact rates at artificial feeding sites. These negative effects could offset the aforementioned benefits and might illustrate a trade-off between the survival of populations and the health of individuals. Usable urban green patches might also exist as sink habitats; inbreeding detrimental to population health could occur owing to reduced movement opportunities in a highly urban matrix. Finally, to enable a complete picture of the interaction between diet and energy budgeting, we will perform a food choice experiment combined with measurements of energetic demands. This will help us to quantify the consequences of urbanization on metabolism and understand the energetic and nutrient constraints of different habitats. The results of this project will not only be of relevance to urban wildlife management and conservation practices, but also for the management of wild animal populations at natural sites. Animals are forced to use cities due the pressure of over-expanding urban habitats, but if cities symbolize sink-habitats species will still need the disappearing forests to survive. Understanding underlying mechanisms and developing appropriate actions to face these contradicting conditions is one of the main future challenges for nature conservation.