City life does not change a small mammal community composition

Abstract

Context Urbanization is a global phenomenon with profound forms of land-use change. Urban areas are characterized by habitat fragmentation and replacement of natural habitat by human-made structures, which alter environmental conditions such as natural resources, light and noise levels, and ambient temperature. Animal communities respond to urbanization in various ways, often showing shifts towards generalist species and declines in species richness. However, mixed results are found in the literature, with neutral or even positive effects on species diversity. Aims Our goal was to investigate whether community composition, species diversity and evenness of terrestrial small mammals vary with increasing levels of urbanization, approximated as impervious surface cover and human population density. Methods We conducted a camera trap survey in 33 gardens in the city of Münster, Germany, and its surroundings. We recorded a total of 25,982 photos with animals (excluding pets). For analysis, we included only photos of the same species captured at least 60 s apart, resulting in a final dataset of 7090 photos. Key results Eight taxa were recorded, with Apodemus spp. dominating (72.6%). The probability of occurrence of all species was not affected by increasing impervious surface cover. We found that community composition, species diversity and evenness do not vary with changing impervious surface cover or human population density. Although associations among species were mostly neutral, trends included a positive association between Myodes glareolus and Crocidura spp., and negative associations between Apodemus spp. and Crocidura spp., and Rattus norvegicus and Sciurus vulgaris. Conclusions Our results suggest that composition, species diversity and evenness of this small mammal community are not affected by the two measures of degree of urbanization, impervious surface cover and human population density. The small mammal community of Münster is likely to be the result of generalist species expressing high phenotypic plasticity to bypass the urban filters explaining our overall neutral results. Implications Urban gardens can harbor a small mammal community as diverse as gardens outside of the city, highlighting the importance of these green areas in the urban matrix. Further studies will be needed to address whether our findings are generalizable to multiple cities in Europe.