Suchergebnisse

Context Records collected when sick, injured or dead animals arrive at wildlife care facilities have potential to offer insights into population declines and identify key threatening processes for conservation and management intervention. Aims Records compiled from a centralised Queensland Government database of koala (Phascolarctus cinereus) arrivals to care facilities across South East Queensland were analysed to explore long- and short-term trends in arrivals in terms of seasonality, causes, outcomes and spatial distribution, with a particular focus on insights hospital records could provide into the potential role of disease in koala population declines. Methods Analysis was conducted on over 22 years of records of koalas arriving at care facilities collated by the Queensland Government. We summarised causes of hospital arrivals and outcomes. We utilised time-series methods to explore short-term cyclic dynamics in the data, and spatial tools to document changes in the distribution of koala arrivals. Key results In the long term, koala hospital arrivals increased modestly from 1997 to 2014, before falling into decline by 2018. Long-term changes are dwarfed by short-term fluctuations, including clear annual cyclic dynamics associated with car strike and dog attack, which peak from August to October each year, likely coinciding with the onset of the koala breeding season. Seasonality is also detected in disease-associated arrivals. Known severe declines in wild koala populations in South East Queensland, an area of intensive urbanisation and associated loss of koala habitat, are not reflected in the overall koala hospital arrival numbers. Our analysis suggests that severe local declines in wild koala abundance have been obscured by increases in the catchment areas from which koalas are entering the hospital network. Conclusions Koala hospital records provide an extensive dataset that can be mined for insights into koala population dynamics and threatening processes. However, interpretation of our findings must consider limitations and biases inherent in data collection. Implications Despite acknowledged shortcomings in terms of bias and data quality, retrospective analysis of records from care facilities can provide important insights for guiding conservation efforts. For example, our findings with respect to seasonality in koala hospital arrivals mirror results reported for other locales, suggesting that cyclic dynamics are not a local phenomenon, but occur more broadly across the species range, with implications for seasonal delivery of conservation actions.

We radio-tracked five male and eight female estuarine crocodiles (Crocodylus porosus) in a non-tidal waterhole in Lakefield National Park in northern Queensland during the late dry/mid-wet season (2003–04) and the following dry season (2004). Individual crocodiles occupied larger home ranges (River Channel Areas (RCA) during the late dry/mid-wet season (10.64 ± 2.86 ha) than in the dry season (3.20 ± 1.02 ha), and males occupied larger home ranges (23.89 ± 2.36 ha) than females (5.94 ± 1.34 ha) during the late dry/mid-wet season. There were no obvious differences in home range between sexes during the dry season. During the late dry/mid-wet season, adult males often travelled long distances along the waterhole while females moved less. During the dry season, movement patterns were quite variable, with no clear difference between sexes. All crocodiles were most active from late afternoon (1500–1800 hours) until midnight. Individual home ranges (RCA) overlapped considerably during the late dry/mid-wet season. The extent of home-range overlap between three adult males and the number of times they either passed each other or were located near each other was particularly striking. Previous research has come to conflicting conclusions about the extent of territoriality in wild estuarine crocodiles, although it has been widely believed that males are highly territorial. The findings imply that large adult male estuarine crocodiles are not highly territorial in non-tidal freshwater systems that are geographically confined.

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.