Conserving biodiversity in urban landscapes: mechanisms influencing the distribution, community assembly and resource use of insectivorous bats in Sydney, Australia
Contributor(s)Law, Bradley, Forest Science Centre, NSW Primary Industries
Banks, Peter B, School of Biological Sciences, University of Sydney
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AbstractUrbanisation affects indigenous fauna in many ways; some species persist and even increase in urban areas, whereas others are lost. The causative mechanisms determining species persistence remain elusive; however an understanding of such mechanisms is crucial to conservation planning. In this thesis, I examined the urban landscape ecology of insectivorous bats in Sydney, Australia, across multiple ecological scales. I used a combination of mensurative and manipulative field examinations to address the mechanisms influencing bat distribution, community assembly and resource use. Firstly, using data collected from ultrasonic bat detectors at a landscape scale, I show that the degree of urbanisation, amount of bushland remaining, and landscape geology, influenced bat activity and structures the bat community into trait-specific groups. Open-adapted bats were associated with areas of greater housing density in more fertile areas, while clutter-adapted bats were associated with greater amounts of bushland occurring on less fertile geologies. I then explored patterns of insect biomass, revealing that landscape geology and habitat loss via urbanisation significantly alters prey biomass and the foraging patterns of bats. Species-specific habitat models were then developed, revealing substantial variation in the sensitivity of species to urbanisation, which was influenced by their biological traits. Using radio-telemetry in a suburban setting I examined fine-scale responses, showing that sensitivity to urbanisation substantially reduced the foraging and roosting range of a clutter-adapted species, Gould&#146;s long-eared bat Nyctophilus gouldi which was restricted to larger remnant bushland (30 ha) for both roosting and foraging. Finally, I show experimentally that interspecific interactions at the scale of a tree hollow, including competition from hollow-using birds and predation by abundant urban mammals, have the potential to alter bat roosting behaviour, rendering hollows a limiting resource and posing a significant disturbance to roosting bats. My results thus demonstrate that biotic and abiotic factors at a combination of ecological scales interact to influence the response of bats to urbanisation. My approach also demonstrates how ecological theory can be used to understand critical ecological functions in cities, and I discuss how these results can be used in conservation planning, to promote bat diversity and conservation in cities.