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In endangered mammals, levels of genetic variation are often low and this is accompanied by genetic divergence among populations. The mountain pygmy-possum (Burramys parvus) is an endangered marsupial restricted to the alpine region of Victoria and New South Wales, Australia. By scoring variation at eight microsatellite loci, we found that B. parvus populations exhibit high levels of genetic divergence and fall into three distinct groups from the northern, central and southern areas of the distribution of this species, consistent with previous assessments of mitochondrial DNA variation. F(ST) values between populations from these regions ranged from 0.19 to 0.54. Within the central area, there was further genetic fragmentation, and a linear association between genetic and geographical distance. This pattern is likely to reflect limited dispersal across barriers despite the fact that individual B. parvus can move several kilometres. Levels of genetic variation within populations were high with the exception of a southern population where there was evidence of inbreeding. From a conservation perspective, all three areas where B. parvus are found should be considered as separate gene pools; management of populations within these areas needs to take into account the low gene flow between populations, as well as threats posed by roads, resorts and other developments in the alpine region. The low genetic variability and inbreeding in the southern population is of particular concern given the high levels of variability in other B. parvus populations.

Physiological variables of torpor are strongly temperature dependent in placental hibernators. This study investigated how changes in air temperature affect the duration of torpor bouts, metabolic rate, body temperature and weight loss of the marsupial hibernator Burramys parvus (50 g) in comparison to a control group held at a constant air temperature of 2 degrees C. The duration of torpor bouts was longest (14.0 +/- 1.0 days) and metabolic rate was lowest (0.033 +/- 0.001 ml O2.g-1 x h-1) at 2 degrees C. At higher air temperatures torpor bouts were significantly shorter and the metabolic rate was higher. When air temperature was reduced to 0 degrees C, torpor bouts also shortened to 6.4 +/- 2.9 days, metabolic rate increased to about eight-fold the values at 2 degrees C, and body temperature was maintained at the regulated minimum of 2.1 +/- 0.2 degrees C. Because air temperature had such a strong effect on hibernation, and in particular energy expenditure, a change in climate would most likely increase winter mortality of this endangered species.

A population of mountain pygmy-possums Burramys parvus was studied at the Mount Blue Cow ski resort in Kosciuszko National Park between 1986 and 1989. Forty-eight individuals were radiotracked during the snow-free months and 21 individuals were tracked during winter over the 3 years of study. Trapping and radiotracking showed that the density, population structure, movements and home range sizes of B. parvus on Mount Blue Cow were strongly correlated with elevation and changed with the season. Female densities were greatest in habitats characterized by deep boulderfields, at high elevations with an abundance of Bogong moths. Males visited the areas where females were located to breed in November-December and then by February, the majority migrated to lower elevations or north and westerly aspects. Females that nested at lower elevations also visited high-elevation habitats to access the high concentrations of Bogong moths, which were the main food source in summer. A high proportion of the juvenile males and some juvenile females dispersed to lower elevations in March and April. The resulting sexual segregation during autumn and winter may be a result of female aggression or scramble competition, but is also explainable by differences in energy requirements, seed availability and hibernation strategies between the sexes. The extraordinarily large nightly and seasonal movements between habitat patches of up to 2 km for females and 3 km for males, sexual segregation and the use of different hibernation sites have important implications for the management of this species. These include the need for movement and dispersal corridors and the conservation of boulder-heath habitats outside the main boulderfields.

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