Since humans evolved, they have influenced and changed their environment, which started with hunting pressure and has culminated in climate change. Urbanized areas are arguably the most altered environments on earth, with the process of urbanization transforming natural landscapes in into human-dominated areas. Previous research has found urbanized areas are associated with higher biodiversity, provide refugee habitats for species from various taxa and support high population densities. However, high urbanization can also lead to declining population numbers, local extinction, higher invasion rates of species and potential yet undescribed consequences. Especially the consequences of elevated stressors, which are not exclusive to cities, but are more pronounced than in natural habitats, still need to be elucidated. Therefore model species for the urban living wildlife have to be identified. The Western European hedgehog (Erinaceus europaeus, hereafter hedgehog ) could serve as such a model species as it is geographically widespread. These days, hedgehogs are found in higher density close to urbanised areas while its numbers are declining in some areas of its range. Furthermore, hedgehogs might suffer from the densification of urban areas. The construction of infrastructure causes fragmentation and fragmentation can impede the movement of individuals. This fragmentation can influence gene flow between subpopulations when there is no or only restricted access to mates. Hedgehogs, in particular, could be affected by their restricted dispersal and susceptibility to barriers. Thus, the species characteristics and ecology make them an appropriate model species to understand the effect of humans on small ground-dwelling overlooked species in cities. Therefore the genetic diversity and behavioural plasticity of hedgehogs in a suitable study site like Berlin have to be investigated. In the first genetic study on hedgehogs in a city of this size (~1050 km²), we found, against our expectations, no genetic structure in the population. In a different analysis approach, we could identify ‘family-clan’ structures, which could be an early sign of inbreeding in subpopulations. With our study on the genetic structure of hedgehogs and the identification of new genetic markers, we provide the foundation for future projects to identify the effects of urbanisation on genetic diversity of hedgehogs and evidence-based population management in future. Together with the results of the ecological studies and effects of disturbance and fragmentation on the behaviour of selected hedgehog populations we can draw a better picture of small mammals in cities. For the ecological studies, we developed novel attachment methods in a species-specific manner. We improved methods by considering the welfare of the studied animals, the cost efficiency and flexibility of the attachment system. This system enabled us to collect spatial and temporal high-resolution data with longer durations than ever before (GPS units). Thus it was possible to follow hedgehogs through an occurring festival in a semi-natural park and in a fragmented zoological garden, identifying population and individual coping strategies, which highlight the behavioural flexibility of hedgehogs. While we were able to show that research is necessary at both the population level and individual level, without continued monitoring of population genetic and individual behaviours using specialized techniques such as ours, we will never be able to fully understand the greater intricacies of such complex ecosystem as we have in urban centres. We now have the technologies and methods to make evidence-based management decisions and harbour species in cities. It is clear, that cities need to give nature space. As long as flora, fauna and funga have enough connections between fragmented “green” areas it might help to sustain healthy populations and could even provide source populations in the process of rural restoration. However, it is also clear that cities are not enough to harbour all wildlife alone in the long-term, especially if the remaining green spaces vanish and cities continue to condense.
