No abstract

Since European colonization, Leadbeater's possum (Gymnobelideus leadbeateri) has declined across its range to the point where it is now only patchily distributed within the montane ash forests of the Central Highlands of Victoria. The loss of large hollowbearing trees coupled with inadequate recruitment of mature ash forest has been predicted to result in a reduction in population size of up to 90% by 2020. Furthermore, bioclimatic analyses have suggested additional reductions in the species' distribution under a variety of climate change scenarios. Using a panel of 15 highly resolving microsatellite markers and mitochondrial control region sequence data, we infer past and present gene flow. Populations in the northern part of the core range were highly admixed, and showed no signs of either current or historical barriers to gene flow. A marginal, isolated and inbred population at Yellingbo was highly genetically differentiated, both in terms of current and historic genetic structure. Sequence data confirmed the conclusions from earlier genetic simulation studies that the Yellingbo population has been isolated from the rest of the species range since before European-induced changes to the montane landscape, and formed part of a larger genetic unit that is now otherwise extinct. Historic loss of maternal lineages in the Central Highlands of Victoria was detected despite signals of immigration, indicating population declines that most probably coincided with changes in climate at the end of the Pleistocene. Given ongoing habitat loss and the recent (February 2009) wildfire in the Central Highlands, we forecast (potentially extensive) demographic declines, in line with predicted range reductions under climate change scenarios.

A combination of fires and logging mean that more than 80% of the montane ash forests inhabited by Leadbeater’s possum (Gymnobelideus leadbeateri) in the Victorian Central Highlands consist of ecologically young stands possessing few trees with hollows. As a consequence, there have been predictions of a substantial decline in Leadbeater’s possum populations over the next 40 years. If this is to be averted, or reduced in extent, then an immediate means of increasing den site availability for the species is required. The results of a recent investigation into nest-box use by the species in lowland swamp forest demonstrate that high rates of occupancy can be achieved by targeting established colonies at sites where the vegetation structure is suitable for box installation. This suggests that nest boxes can be an effective means of increasing den-site availability for the possum, and therefore have considerable potential to contribute to the species’ conservation in the short term. Such measures should be applied in conjunction with altered forestry practises that better provide for the retention and future provision of mature hollow-bearing trees.

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Radio-tracking is a key technique for monitoring threatened species during ecological research and reintroduction programs. In the case of the endangered eastern barred bandicoot (Perameles gunnii), it has not been possible to radio-track for extended periods (≥3 months) due to difficulties in reliably and safely attaching radio-transmitters. In this study we compared eight attachment methods. Transmitters weighing 1.2–28 g were either mounted with adhesive, attached to a collar or implanted into the peritoneum. Intraperitoneal transmitters were superior in terms of attachment duration, but were considered inferior overall as they could not be fitted in the field and had a very short detection range once implanted (≤50 m). Retention times for external transmitters differed greatly between methods, ranging from 1 to 102 days. One tail-mount attachment technique caused minimal adverse effects but another caused tail amputation in one animal, and both had short retention times (3–33 days). Neither of the glue-on transmitter methods resulted in substantial periods of attachment (2–30 days) and flank-mounted transmitters also caused severe skin trauma. Radio-collars were generally retained for longer periods (42–102 days) but resulted in limb entanglement when they were fitted too loosely or subconjunctival haemorrhages when they were too tight. Cable tie collars are recommended as the most suitable attachment technique for bandicoots, as when fitted correctly they cause minimal impact to individuals and permit long retention times, but precise fitting is essential.