Parasites in the city: How is the impact of parasites on wild animal welfare affected by urbanization?
Grantee: Amanda Trask
Institutions: Institute of Zoology (IOZ), Zoological Society of London (ZSL), United Kingdom
Grant amount: $199,941
Grant type: Challenge grant
Focal species: Eastern grey squirrel (Sciurus carolinensis)
Conservation status: Least concern
Disciplines: Infectious disease, population ecology
Research location: United Kingdom
Project summary
Parasitism is likely a key determiner of wild animal welfare, while rapidly increasing urbanisation presents novel challenges and welfare threats, yet the extent that parasitism and urbanisation impact wild animal welfare, both independently and synergistically, remains a major knowledge gap. An individual’s parasite infection status, and the associated welfare impacts, is dependent on parasite exposure risk and susceptibility. Urbanisation may alter exposure risk, for example through changes to population density and resource distribution, and susceptibility, for example through altered host immune function from exposure to urban stressors. Urbanisation may also compound impacts of parasitism, if chronically stressed individuals are less able to cope with further welfare challenges, resulting in synergistic negative welfare effects. Furthermore, welfare impacts of parasites and urbanisation may vary across sex- and life-stage classes, for example due to hormonal influences and changes in immune function with chronic exposure to urban pollution.
We will address this knowledge gap, using grey squirrels from UK sites across an urbanisation gradient. We will use detailed individual-level data on parasite loads and physical and physiological welfare indicators, collected from dead squirrels killed as part of non-native species management, to determine welfare impacts across sites varying in degree of urbanisation, and across sexes and life stages. Then, we will use behavioural indicators from camera trap data to determine associations between population-level welfare, parasite prevalence and degree of urbanisation. Finally, we will estimate ‘welfare expectancy’ of individuals from different populations using sex- and life-stage specific welfare scores. We will expand on current theory and develop a modelling tool to incorporate demographic and environmental stochasticity in welfare states into population models, to aid prediction of how increasing urbanisation may impact wildlife welfare in the future. This study will provide vital knowledge to aid understanding and prediction of the experience and future responses of wild animals to parasites in the context of increasing urbanization, facilitating design and integration of welfare-friendly urban environments for wildlife.
Why we funded this project
Gray squirrels are abundant, they live in close proximity to humans, and they could benefit from welfare interventions such as wildlife fertility control in the near future. Gray squirrels are not native in the UK, where this study will be conducted, and the welfare of non-native species is generally understudied or undervalued compared with native species of conservation interest. This project provides a special opportunity to take advantage of data from squirrels who are being killed as part of a government program, and to access valuable metrics that are hard to measure non-invasively, thereby creating from their deaths an opportunity to gain valuable insights that could ultimately help other squirrels. In addition to their good range of welfare indicators, we appreciate that this project will consider sex- and age-specific variation in welfare impacts and attempt to estimate “welfare expectancy” at a population level.