Talk by Dean Heinze. Jan 21, 2006.

Three populations. There are three genetically distinct populations at Mt Buller, Mt Hotham to Mt Bogong, and at Mt Kosciuszko. The populations have been separated for probably hundreds of years. The Mt Buller population was found in 1966.

Burramys. It is the only Australian alpine mammal. There were an estimated 1900 breeding pairs pre-2003 wildfires.

Burramys parvus means small rock mouse. It is the largest species of pygmy possum. It has grey to brown fur and is yellow beneath. It is long-lived (up to 12 years). It is a marsupial hibernator and is restricted to alpine and sub-alpine areas. It has a prehensile and scaly tail and weighs 30 - 80 grams. The larger weight is its pre-hibernation weight. A particular feature is its enlarged and serrated pre-molar teeth.

Habitat needs. Pygmy Possums have very specific habitat requirements. They require boulders in alpine areas on the edge of heath. Other residents of the boulder areas are the Bush Rat and Dusky Antechinus. A shrub layer is needed. Hard-shelled seeds are stored for winter. Important shrubs are Mountain Plum Pine, Beard Heath, Native Raspberry, Tall Rice-flower, Dusty Daisy-bush and Alpine Mint-bush.

They will not move through grass so some populations are isolated from others. The home ranges are around a patch of granite or basalt boulders. Attempts are being made with the operators of ski resorts to improve their habitat.

Radio tracking proved that they were following the Native Raspberries as they ripened. They are able to crack hard-shelled seeds with their pre-molar teeth.

Breeding. Males hibernate at lower altitudes than the females, and move upwards in spring to mate. The gestation period is 13-16 days, and young are in the pouch for 30 days. They leave the nest after 30-35 days. Females then put on fat quickly and hibernate in early March. This gives the young the opportunity to have Bogong Moths for food. The females drive the males out as soon as mating is over.

The Alpine Road cuts through the corridor through which the males have to pass. The rock "tunnel of love" was constructed to get them safely under the road. Almost as soon as it was completed the males were using it. Tunnels are used at The Blue Cow (NSW) and are being constructed at Mt Buller.

There are skewed and female-biased sex ratios. At Mt Hotham there is a ratio of 1 male to 6 females. At Mt Buller where the population is in trouble the ratio is one male to 20 females.

The nests are primarily made up of moss and some grass under a ledge in the boulder fields. The young work their way through the nest to reach the mother.

Pouches are down-facing. There are four teats. They give birth to up to 11 young, but only four can survive. There are practically no natural predators but they are predated by foxes, cats, and possibly dogs.

Hibernation. Hibernation is a series of extended torpor bouts of up to 20 days, broken by an arousal for one day to feed on stored resources. The optimum hibernation temperature is 2-2.7 ^oC.

Wildfire 2003. In January 2003 lightning strikes started many fires across the mountains. At Mt McKay the population does not live in boulders but in heath. The possums still had cover of roots, but it was the fringe area of habitat that was burnt and there are still some areas of habitat left. The Plum Pines live a long time and concern was held about these plants. Some Plum Pines sprouted and then died. The area is now dominated by Alpine Pepper.

Patches of 80% habitat was burnt at Mt Hotham. Mt Koskiuszco was approx 80% burnt, and Mt Buller was unburnt. High mortalities during the fire are from suffocation, exposure etc. There is now reduced protective cover, a loss of food-producing plants, and fewer hibernation sites. There is a high mortality rate with juveniles and adult males, and competition in unburnt areas until the shrub layers regrow.

Global warming will cause problems with reduced snow cover. Competition for food from other species, especially the Agile Antechinus and mountain rats.

A management issue with the road at Mt Hotham is silt getting in between rocks and filling the boulder gaps that the possums need. Another major threat to the alpine eco-system are the willows that are getting into the bog areas and drying them out.

The Bogong Moths arrive in waves in Spring and leave again in March. They are full of fat when they arrive and are very nutritious. They migrate up to 600 km, mostly to the self-mulching soils in the Murray-Darling basin. Their numbers are probably declining which bodes ill for all of the creatures which rely on them for food.

Fire. Since the fire, the numbers of Pygmy Possums have increased at Mt Loch and Mt Hotham, as other animals have crowded into the unburnt areas. Numbers have dropped at Mt McKay. Of concern are the number of females that have dropped or aborted their young. Whether this will cause future problems is still to be seen.

Migration. Penelope Possum was first caught in 2001 and again in 2006 at sites 15 km apart. How far had she really travelled?

Long-term monitoring. A study of skinks post-fire found that large numbers had survived but numbers dropped dramatically in the next few years. This shows that the Pygmy Possums need to be monitored for a number of years after a fire for an understanding of the final effects of the results of fire.

Estelle Adams