The effects of urbanization on physiological indicators of welfare in bats

Studentship strategic priority area: Biodiversity
Keywords: Urbanization, glucocorticoids, bat, indicator, stress

Abstract: Changes in land use from an increasing human population presents a major challenge for biodiversity (Grimm et al. 2008). Several studies have documented the impacts of urbanization on wildlife due to habitat loss and fragmentation, chemical, light and noise pollution, predation from pets and road mortality (Russo & Ancillotto 2015). While some aspects of urbanization have immediate lethal effects, others act more slowly or may vary between years or seasons. For example, urban heat might benefit some species, but be detrimental to others at certain times of the year (e.g. hibernators in winter).

Bats are both one of the most diverse mammalian groups represented in urban environments (Jung & Threlfall 2016) but also one of the most threatened (Jones et al. 2009). Urban and rural roost sites are likely to differ in quality on the basis of chemical, noise and light pollution, temperature and thermal variability, disturbance and access to food and water. Some bat species are relatively common in urban areas (e.g. Pipistrellus pipistrellus in Europe), and have been described as 'urban-adaptors'. However, recent work has indicated that the activity of even these species decreases with increasingly urbanized landscapes (Lintott et al. 2016). The mechanism for this is unclear; most work on bat responses to urbanization has focused on foraging and roosting patterns with little information on physiological effects.

This PhD will use a number of novel and non-invasive welfare indicators to compare levels of physiological stress in wild and museum specimens of bats from urban and rural environments in combination with habitat modelling. Glucocorticoids are commonly used indicators of baseline stress levels, and are generally assayed from blood. However, non-invasive faecal glucocorticoid measurements have recently been validated to assess chronic stress in a bat (Eptesicus isabellinus; Kelm et al. 2016). Glucocorticoids can also be extracted from hair, providing a hormone profile that tracks the period of hair growth. This will be carried out in bats for the first time in this project.

The aim of this project is to investigate the effects of urbanization on indicators of welfare in bats. Key objectives include:
1. Validating novel physiological indicators of welfare in bats
2. Testing for variation in glucocorticoid levels along a gradient of increasing urbanization
3. Testing for differences in the signature of chemical pollutants in bat fur between urban and rural populations
4. Modeling population growth from habitat use and composition to inform conservation and survey effort
LG will investigate these questions in two common UK bat species, the common pipistrelle (Pipistrellus pipistrellus) and soprano pipistrelle (Pipistrellus pygmaeus), to provide insights on the physiological mechanisms underlying urban declines in bats. It is anticipated that the findings of this work will inform landowners and policymakers on conservation management.