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Miller E.J.,University of New South Wales | Miller E.J.,University of Sydney | Eldridge M.D.B.,College Street | Morris K.D.,Western Australian Wildlife Research Center | And 3 more authors.
Conservation Genetics | Year: 2011

Isolation and restricted gene flow can lead to genetic deterioration in populations. Populations of many species are increasingly becoming fragmented due to human impacts and active management is required to prevent further extinctions. Islands provide an ideal location to protect species from many mainland threatening processes such as habitat loss and fragmentation, disease and competition/predation from introduced species. However their isolation and small population size renders them prone to loss of genetic diversity and to inbreeding. This study examined two endemic and one introduced population of tammar wallaby (Macropus eugenii) on three islands in the Houtman Abrolhos Archipelago, Western Australia: East Wallabi (EWI), West Wallabi (WWI) and North Islands (NI). Nine autosomal and four Y-linked microsatellite loci, and sequence data from the mitochondrial DNA (mtDNA) control region were used to examine the impact of long-term isolation (EWI and WWI) and small founder size (NI) on genetic diversity and inbreeding. This study found all three populations had low genetic diversity, high levels of effective inbreeding and increased frequency of morphological abnormalities. Isolation has also led to significant inter-population genetic differentiation. These results highlight the importance of incorporating genetic management strategies when utilising islands as refuges for declining mainland populations. © 2011 Springer Science+Business Media B.V.

De Tores P.J.,Western Australian Wildlife Research Center | Elscot S.,Western Australian Wildlife Research Center
Wildlife Research | Year: 2010

Context. Long-term land-use decisions potentially affecting the conservation status of rare fauna are often based on a dearth of relevant biological information and population estimates are regularly derived from ad hoc methodologies. This can significantly affect the outcomes from development assessment and approval processes. Aim. Our aims were to apply distance-sampling techniques to derive robust, quantitative estimates of the population size of a threatened arboreal marsupial, the western ringtail possum (Pseudocheirus occidentalis Thomas, 1888), demonstrate the advantages of this approach and, in doing so, provide conservation managers, decision makers and consultants with a reliable framework for surveying the species. Methods. We used line-transect sampling to derive estimates of density and abundance for P. occidentalis at two sites in south-western Western Australia where estimates were previously derived through ad hoc techniques. Key results. Our findings support the assertion that previous surveys of P. occidentalis populations have underestimated the population size to a varying extent at both of our survey sites. Land-use and development-application decisions have previously been based on similar surveys. Conclusions. Distance sampling, if applied routinely when surveying P. occidentalis, will reduce the uncertainty associated with derived estimates of abundance. Implications. Appropriate use of distance-sampling methods will enable managers and decision makers to assess more quantitatively the potential effect from, and place appropriate approval conditions on, proposals that modify or destroy P. occidentalis habitat. The use of the program Distance will enable such decisions to be based on robust, repeatable estimates of population size, with quantified confidence limits and variance estimates. © CSIRO 2010.

Clarke J.,Murdoch University | Clarke J.,Australian Department of Primary Industries and Fisheries | Warren K.,Murdoch University | Calver M.,Murdoch University | And 3 more authors.
Journal of Wildlife Diseases | Year: 2013

Health screening of animals before translocation is important to minimize the risk of pathogen transmission between sites and species. Reintroduction has been incorporated into management of the endangered western ringtail possum (Pseudocheirus occidentalis) to mitigate for habitat loss within the species' core range in southwestern Australia. Between November 2005 and March 2008 we screened 47 wild and 24 captive P. occidentalis and 68 sympatric common brushtail possums (Trichosurus vulpecula hypoleucus) for infectious diseases that might compromise possum survival or fecundity at translocation sites. We found no evidence that infectious disease limits translocation success, and neither possum species showed evidence of infection with Salmonella spp., Toxoplasma gondii, Leptospira spp., or Chlamydophila spp. Antigen of Cryptococcus gattii was detected in one T. v. hypoleucus but was not of pathologic significance. Hematologic and serum biochemical reference ranges were determined for 81 wild and 24 captive P. occidentalis. Site differences were identified for red blood cell count, hemoglobin, albumin, urea, and globulin, suggesting that habitat quality or nutrient intake may vary among sites. Differences between wild and captive values were found for several parameters. These data are useful for health evaluations of injured P. occidentalis and the future monitoring of wild populations. © Wildlife Disease Association 2013.

Start A.N.,Western Australian Wildlife Research Center | Burbidge A.A.,Western Australian Wildlife Research Center | McDowell M.C.,Flinders University | McKenzie N.L.,Western Australian Wildlife Research Center
Australian Mammalogy | Year: 2012

To assess the current status of mammals in relation to mean annual rainfall and to improve knowledge of the original mammalian assemblages in tropical Western Australia, extant terrestrial mammals and subfossil mammalian remains were sought along a rainfall gradient in two parallel ranges in the Kimberley, Western Australia. As expected, extant mammal species richness decreased with decreasing rainfall. Data from other studies in higher-rainfall areas complemented this conclusion and a parallel decline in trap success implied an overall decline in abundance, although numbers of two rodents (Rattus tunneyi and Zyzomys argurus) were highly variable. Small rodents were rare. Subfossil deposits were biased by accumulation processes, with most attributable to tytonid owls. They largely consisted of rodent and, to a lesser extent, small dasyurid bones and there was a high level of consistency in the proportional composition of many common species across the rainfall gradient. Most deposits appear to predate the introduction of stock in the 1880s and some may be much older. All species persist in the study area except two Notomys spp. and three Pseudomys spp. Both the Notomys and one Pseudomys are apparently undescribed, extinct species. However, there were marked ratio differences between subfossil and modern assemblages. Although specimens of species larger than those taken by tytonid owls were scarce, their occurrences were broadly consistent with the modern understanding of distributions. © 2012 Australian Mammal Society.

Berry O.,University of Western Australia | Berry O.,CSIRO | Algar D.,Western Australian Wildlife Research Center | Angus J.,Western Australian Wildlife Research Center | And 3 more authors.
Journal of Wildlife Management | Year: 2012

Globally, invasive predators are major pests of agriculture and biodiversity and are the focus of comprehensive control programs. Because these species are typically elusive, wary of traps, and occur at low densities, their fundamental population dynamics are difficult to determine and quantitative evaluations of control programs are rarely conducted. Noninvasive DNA analysis has the potential to resolve this long-standing limitation to pest management. We carried out a landscape-scale experiment to quantify reduction in the abundance of a red fox (Vulpes vulpes) population when baited with sodium fluoroacetate (1080) poison (the most widely used method of fox control in Australia). We collected fox hairs with hair snares during 4 4-day sessions over the course of 6 months at a site in semi-arid Western Australia. The first session took place in late summer just prior to when juvenile foxes typically disperse, and the final session followed aerial baiting with 1080 poison. We obtained consensus microsatellite genotypes from 196 samples, and used them to conduct both spatially explicit and open model capture-recapture analysis. Twenty-eight percent of trap nights yielded hair samples suitable for identification of individual foxes, which is more than an order of magnitude greater than trapping rates reported with conventional techniques. Fox density changed little during 3 pre-baiting sessions and averaged 0.73 foxes/km 2 (±0.33 SE), which is less than most previous trap-based estimates for Australian foxes. Density dropped significantly in response to baiting to 0.004 foxes/km 2. Prior to baiting, the apparent survival of foxes remained static (0.72 ± 0.14 SE), but in response to baiting it dropped precipitously and was effectively zero. This experiment provides the first quantitative assessment of the effectiveness of 1080 poison baiting for reducing fox density, and in this case demonstrates it to be a highly effective method for culling foxes from a region. Further, it demonstrates that noninvasive DNA analysis will provide significantly more data than conventional trapping methods. This method is likely to provide greater precision and accuracy than conventional methods and therefore result in more robust evaluations of management strategies for the fox in Australia, and for cryptic species elsewhere. © 2011 The Wildlife Society.

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