Movement patterns of an arboreal marsupial at the edge of its range: a case study of the koala
Nicole Davies1*, Galina Gramotnev2, Leonie Seabrook2,3, Adrian Bradley1, Greg Baxter2, Jonathan Rhodes2,3, Daniel Lunney4,5 and Clive McAlpine2,3
1School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia.
2The University of Queensland, Landscape Ecology and Conservation Group, School of Geography, Planning and Environmental Management, St Lucia, Queensland 4072, Australia.
3The University of Queensland, Environmental Decisions Group, St Lucia, Queensland 4072, Australia.
4Office of Environment and Heritage NSW, PO Box 1967, Hurstville, New South Wales 2220, Australia.
5School of Veterinary and Life Sciences, Murdoch University, Perth, Western, Australia.
Background: Conservation strategies derived from research carried out in one part of the range of a widely distributed species and then uniformly applied over multiple regions risk being ineffective due to regional variations in species-habitat relationships. This is particularly true at the edge of the range where information on animal movements and resource selection is often limited. Here, we investigate home range size, movement patterns and resource selection of koalas Phascolarctos cinereus in the semi-arid and arid landscapes of southwest Queensland, Australia. We placed collars with GPS units on 21 koalas in three biogeographic regions. Home range sizes, resource selection and movement patterns were examined across the three regions.
Results: Habitat selectivity was highest at the more arid, western edge of the koala’s range with their occupancy restricted to riparian/drainage line habitats, while the more easterly koalas displayed more variability in habitat use. There was no significant difference between home range sizes of koalas at the western edge of the range compared to the more easterly koalas. Instead, variability in home range size was attributed to spatial variations in habitat quality or the availability of a key resource, with a strong influence of rainfall and the presence of freestanding water on the home range size of koalas. Within a 580 m spatial range, movement patterns of male and female paths showed a tortuous trend, consistent with foraging behavior. Beyond this spatial range, male paths showed a trend to more linear patterns, representing a transition of movement behavior from foraging to breeding and dispersal.
Conclusions: The difference in home range movement patterns and resource use among the different koala populations shows that behavior changes with proximity to the arid edge of the koala’s range. Changes in home range size and resource use near the range edge highlight the importance of further range-edge studies for informing effective koala conservation and management actions, especially when developing species-specific adaptation responses to climate change.