Shifts in macropod home ranges in response to wildlife management interventions

Context. Understanding how the individual movement patterns and dispersion of a population change following wildlife management interventions is crucial for effective population management. Aims. We quantified the impacts of two wildlife management strategies, a lethal intervention and a subsequent barrier intervention, on localised populations of the two most common macropod species in Tasmania, the Tasmanian pademelon (Thylogale billardierii) and the red-necked wallaby (Macropus rufogriseus rufogriseus). This manipulation allowed us to examine two competing hypotheses concerning the distribution of individuals in animal populations - the Ideal Free Distribution (IFD) hypothesis and the Rose Petal (RP) hypothesis. We predicted that the RP would be supported if individuals maintained their previous home ranges following intervention, whereas the IFD would be supported if individuals redistributed following the management interventions. Methods. The movement patterns of T. billardierii and M. r. rufogriseus were tracked using GPS technology before and after the two management interventions. Key results. Following lethal intervention, pademelons and wallabies (1) maintained their home-range area, (2) increased their utilisation of agricultural habitat and (3) shifted their mean centroid locations compared with the pre-intervention period. Following barrier intervention, pademelons and wallabies (1) maintained their home-range area, (2) decreased their utilisation of agricultural habitat and (3) shifted their mean centroid locations compared with the pre-intervention period. Conclusions. On the basis of the individual responses of macropods to the management strategies (1) lethal intervention appeared to induce small shifts in home-range distributions of those remaining individuals in the population with home ranges overlapping the areas of lethal intervention and (2) barrier intervention is likely to induce whole-scale population movements of the animals that survive the lethal intervention in their search of an alternative food source. Both species displayed spatial and temporal shifts in their home-range distributions in response to lethal and barrier interventions that appear to conform broadly to predictions of IFD, at least in the timeframe of the present experiment. Implications. Wildlife management strategies, which are increasingly constrained by ethical, socio-political and financial considerations, should be based on ecological and behavioural data regarding the likely responses of the target population.