Roshier, David A.

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  • Data package
    Data from: Spring foraging movements of an urban population of grey-headed flying foxes (Pteropus poliocephalus)
    (2021-03-09) Roshier, David A.; Boardman, Wayne S.J.
    Flying foxes provide ecologically and economically important ecosystem services but extensive clearing and modification of habitat and drought combined with the planting of commercial and non-commercial trees across various landscapes, has meant flying foxes in Australia are increasingly seeking foraging resources in new areas. In 2011, grey-headed flying foxes formed a camp in Adelaide, South Australia, outside their previously recorded range. We used global positioning system telemetry to study the movements and foraging behaviour of this species in Adelaide in spring (September to November) 2015. High-frequency location data were used to determine the foraging range and the most frequently visited foraging sites used by each bat which were ground-truthed to identify forage plants. A total of 7239 valid locations were collected over 170 nights from four collars. Despite being a highly mobile species, the mean core foraging range estimate was only 7.30 km2 (range 3.3–11.2 km2). Maximum foraging distance from the camp in the Botanic Park was 9.5 km but most foraging occurred within a 4-km radius. The most common foraging sites occurred within the residential area of Adelaide and included introduced forage plant species, Lemon-scented gum (Corymbia citriodora) and Port Jackson fig (Ficus rubiginosa). Other observed movement activities included dipping behaviour on inland and marine waters and travel across flight paths around Adelaide airport. Our findings suggest that urban habitats in Adelaide provide sufficient foraging resources for grey-headed flying foxes to use these areas exclusively, at least in spring. This creates substantial opportunities for bats to interact with humans and their infrastructure.
  • Data package
    Data from: Space use and interactions of two introduced mesopredators, European red fox and feral cat, in an arid landscape
    (2021-12-20) Roshier, David A.; Carter, Andrew
    Introduced mammalian predators are drivers of species decline and extinction globally. The successful management and control of introduced mammalian predators is dependent on some knowledge of space use and movements in order to target a population and monitor outcomes. In Australia, these tasks are made complex as there is more than one significant introduced mammalian predator, namely the European red fox Vulpes vulpes and feral cat Felis catus, the landscapes are vast, and individual-level interactions between predators are little studied. The impact of these two introduced predators is large and a significant factor in the extinction of many of the country’s small- to medium-sized mammals, either regionally or globally. In a three-year study, we used high-frequency location data, the deployment of the latest GPS tracking technologies, and recent advances in statistical modeling to examine how these two species distributed themselves in space, the degree to which individual distributions overlapped, intra- and interspecific interactions, and temporal patterns of activity in an arid landscape. In the absence of an apex predator, the two introduced mesopredators showed large differences in how they distribute themselves across the landscape and interact with conspecifics. The red fox mostly occupies defined territories, while most feral cats roam apparently independent of each other with occasional periods of frequent interaction with conspecifics of either sex. Intraspecific attraction was strongest in cats, while interspecific avoidance was observed in both directions. The home ranges of feral cats that were range-resident were 3–3.5 times larger than foxes in the same landscape. Notably, we observed long-distance movements in feral cats and some were displaced up to 164 km from their point of release. A greater portion of the feral cat population were non-sedentary and therefore likely less amenable to local control efforts than foxes. Given the different patterns of distribution in time and space, the reliable monitoring of population trends or estimates of abundance will necessarily differ in extent, intensity, or duration for the same level of precision and/or require a different method for monitoring each population.