Fox and the city: understanding the influence of urban environment on the disease ecology of red foxes

Abstract

The “city fox phenomenon” is a relatively new one. The presence of established Red fox (Vulpes vulpes) populations in highly urbanised areas was first reported from London at the beginning of the 20th century; since then the number and frequency of these reports have multiplied and this is now consider a global trend. The causes of this phenomenon remain largely unknown, although it is speculated that that changes in the structure of the urban fabric (such as the expansion of low-to-medium density housing) have created new suitable habitats for foxes to colonise. The presence of foxes in urban areas is especially relevant since they carry parasites and diseases that are responsible for some serious pathologies in humans (e.g. rabies, alveolar echinococcosis). Therefore, the effect of living in urban areas can have on the prevalence of zoonotic parasites in wild foxes has been extensively investigated. The results of these studies are contradictory, finding both increases and decreases in parasite prevalence, depending on the parasite species, study location or both. This is hardly surprising given the complexity of urban landscapes; even finding a comprehensive definition of what is urban has proven a difficult (and yet unsolved) challenge. It is therefore important to consider different aspects of urban areas and the effects they can have on the disease ecology of urban foxes (including both behavioural, physiological and epidemiological aspects). With my thesis, I aim to deconstruct urban environment isolating measureable metrics that can be used to understand the effect of urbanisation on the parasite community of red foxes. I combine practical and theoretical approaches, using both field surveys, laboratory analysis and statistical modelling in order to understand what drives patterns of infection in a wild mammal living in a highly anthropogenic environment. In chapter 2, I tested the use of stable isotopes analysis to detect and quantify anthropogenic food consumption between urban and rural foxes, as this has been linked to profound changes in the host-parasite dynamics in other urban carnivores. In chapters 3 and 4, I explored spatio-temporal dynamics in the gastrointestinal parasite community of urban foxes from the city of Edinburgh (UK). I used several metrics measuring different aspects of urban environment (i.e. human population density, road cover density and greenspace cover) to understand how the prevalence of these parasite vary across space (chapter3) and characterise longitudinal dynamics of infection (chapter4). Finally, in my fifth chapter, I use spatio-temporal hierarchical models to analyse a large dataset of fox infection data sourced from studies carried out across Europe, in order to characterise the overall effect of urbanity on parasite prevalence in foxes. Altogether these findings contribute to the understanding of how urban environment influences the disease ecology of red foxes in particular and wild mammals in general; I developed tools to disentangle the complex and multi-layered effect of urban environment on the disease ecology of urban dwellers, contributing to the development of the field of both urban and disease ecology.