Human population is growing steadily (Goujon, 2019) and with this growth landscapes have been altered trough anthropogenic activities (Chase & Chase, 2016). An increasing amount of natural and semi-natural habitat is being transformed to provide residential space and associated infrastructure. Habitat transformation and loss of habitat connectivity exposes wildlife to new challenging conditions and novel environmental pressures including noise, chemical and light pollution (Grimm et al., 2008). Not all species can cope with these extensive and rapid changes. Urbanisation is identified as one of the main reasons for biodiversity loss (Altherr, 2007; Concepción et al., 2015; Luck & Smallbone, 2010; McKinney, 2006). Vertebrate loss is typically considered to be worst in urbanised areas because of intense and long-term disturbances that permanently alter habitats and depreciate food webs (Lombardi et al., 2017; McKinney, 2008). Nevertheless, there are always animal species that have adjusted to city life, so-called urban dwellers. An outstanding example of a successful urban dweller is the red fox (Vulpes vulpes). Foxes appear to be increasingly moving into human settlements throughout their range. Examples include Oslo, Norway (Christensen, 1985), Arhus, Denmark (Nielsen, 1990), Toronto, Canada (Adkins & Stott, 1998), Zurich, Switzerland (Gloor, 2002), or (in my focal area around) Berlin, Germany (Börner et al., 2009). Detailed knowledge of animal communities, food and competition relationships among the species, as well as species movement patterns and health status allows us to better understand the dynamics and predict the resilience of an ecosystem (Leibold et al., 2004). We need to know which characteristics allow species to persist in urban areas to prevent human-wildlife conflicts and promote biodiversity in cities. Identifying the biological traits favouring synurbisation is decisive to inform current management as well as to generate predictions for the future. In order to understand why the red fox is so successful in our anthropogenic world, we have to study different aspects of its ecology in, both, rural and urban settings. Therefore, this thesis investigates the diet, parasite spectrum and resting behaviour of red foxes along an urbanisation gradient in Berlin and Brandenburg (Germany). The diversity of these topics required the application of different analytical methods. For the investigation of the dietary strategies of rural and urban foxes, food niches were discovered using stable isotope analysis and compared with potentially available food items using Bayesian isotope mixing models (chapter 1). To study the diversity of helminths in the intestinal tract of foxes along a rural-urban gradient and to uncover environmental drivers of helminth communities I applied rarefaction curves, joint species distribution modelling (jSDM) and non-metric multidimensional scaling (NMDS) to helminth presence-absence data obtained by DNA metabarcoding. Finally, I compared the resting behaviour of foxes from Brandenburg and city foxes from Berlin using high resolution GPS and acceleration data. The assignment of behaviours based on the acceleration data served to determine temporal patterns of resting behaviour. Recurse analysis and the application of clustering algorithms allowed the identification of resting sites and their use. Our investigation on the red fox diet (Chapter 1) shows that dietary range of urban red foxes is smaller compared with that of rural conspecifics. Furthermore, higher δ13C values and lower δ15N values of urban foxes suggest relatively high input of anthropogenic food sources of urban foxes. Low within-individual variation compared to the between-individual variation lead to the conclusion that generalist fox populations consist of individual food specialists in urban and rural populations. Main results of the parasitological investigation (Chapter 2) show that the helminth diversity in the city Berlin is lower compared to surrounding rural Brandenburg and male red foxes tend to have higher helminth diversity than females. Diet features can drive helminth communities in red fox populations. Additionally, with increasing human population density, helminths transmitted via diet are less prevalent than pet-related helminths. Finally, I investigated habitat-dependent differences in resting patterns of red foxes from Berlin and Brandenburg (Chapter 3) and results revealed that urban foxes tend to rest more, with their resting behaviour concentrated during the day compared to rural red foxes. This increase in daily rest behaviour is reflected in an increased number of rest events. Moreover, the long-term resting events of city foxes last longer than those of foxes from Brandenburg. Even if rural foxes spend less time resting, rural red foxes of Brandenburg tend to have more resting sites compared to Berlin foxes. Overall, dietary specialisation and the use of anthropogenic food resources, in particular, have an overarching impact on the ecology of urban foxes. If proper food supply has such an extensive influence on the ecology, behaviour and lifestyle of red foxes, management strategies should focus on this topic. Reduced food availability would probably increase the competitive pressure within the fox population, reduce population density and thus also the contact rate between humans, domestic animals and foxes. Human-wildlife conflicts in the city could thus be reduced and the general acceptance of wild animals in the city increased. This could ultimately lead to the sharing of urban areas by humans and wildlife.