Long-term field-based study of the Mountain Brushtail Possum

A project undertaken at The Centre for Resource & Environmental Studies, The Australian National University, Canberra and managed by David Lindenmayer.

This project is a long-term field-based study of the Mountain Brushtail Possum and aims to provide new insights into the ecology, population dynamics and life history of this long-lived marsupial. The proposed work will have significant implications for the conservation of the Mountain Brushtail Possum, particularly for predicting its response to logging-induced habitat changes and estimating the species’ prospects for long-term persistence in Australian forests designated for paper and wood production. For example, the results of the investigation will help mapping and planning refugial conservation areas for wildlife conservation within wood production forests. This will, in turn, assist the improved integration of wildlife conservation and wood production in multi-use landscapes. The project is based around a trap-recapture study that has been running since 1991 at a 35 ha site at Cambarville in the montane ash forests of the Central Highlands of Victoria.

The project has been proceeding excellently since funding was provided by the Hermon Slade Foundation. An average of 35 captures (with rapid release) has been made in each of the field trips completed to date. A major finding from the work to date has been that we have discovered that there is in fact not one but two species of Mountain Brushtail Possums – this is an extraordinary finding – the discovery of new species of large Australian mammals are rare. The current focus of the work is to integrate data on the demographics of animal populations from field trapping with genetic data derived from ear tissue samples collected from trapped animals captured at our study site since 1991. More than 200 animals are included in the trapping and genetic profiles in the study. Genetic analyses are taking place at the Center for Conservation Biology at Brookfield Zoo in Chicago. This work is well advanced and fascinating new patterns of paternity and maternity are arising from these analyses. Work to date is showing that young adult females produce predominantly male young and only switch to producing female offspring toward the end of the effective breeding life (at greater than 10 years of age). Young females also have a high probability of inheriting their mother’s home ranges. In cases where this occurs, these females have higher rates of fecundity than when an empty territory is occupied by a new female unrelated to the previous incumbent. Further genetic work is required to confirm these preliminary findings. A spatial analyses of territories at our study site is suggesting that females in particular territories – especially those near creeks - are far more likely to produce offspring that reach independence than females elsewhere in the area under investigation. These findings are consistent irrespective of the climate conditions prevailing for particular field seasons. Work on the population of the Mountain Brushtail Possum at Cambarville is continuing and new findings will begin being published as a series of scientific papers in coming 12-18 months.

Publications

LINDENMAYER, D.B., Dubach, J., and Viggers, K.L. (2002) Geographic dimorphism in the Mountain Brushtail Possum – the case for a new species. Australian Journal of Zoology, 50, 369-393.

Viggers, K.L., and LINDENMAYER, D.B. (2002). The other brushtail possum. Nature Australia Spring 2002, 47-55.

Viggers, K.L. and LINDENMAYER, D.B. A review of the biology of the Mountain Brushtail Possum. In: Goldingay, R.L. and Jackson, S. (Editors). Possums and Gliders. CSIRO Publishing, Melbourne. (in press).

Viggers, K.L. and LINDENMAYER, D.B. (2000). A population study of the Mountain Brushtail Possum, in the Central Highlands of Victoria. Australian Journal of Zoology, 48, 201-216.

Measurements such as this one of the head length on this sedated Mountain Brushtail Possum have been used to differentiate two distinct species – the Short-eared Possum that ranges from central NSW to central Queensland, and the Mountain Brushtail Possum that is distributed south from Sydney to central Victoria.

Montane ash forests where the Mountain Brushtail Possum occurs are also used extensively for timber and paper production. Current clearfelling methods are known to have significant negative impacts on populations of the species.

The Short-eared Possum – a new species recently separated from the Mountain Brushtail possum by workers supported by the Herman Slade Foundation. Differences in ear length, foot length, tail structure and genetic variability distinguish the two species.

An adult animal emerging from a tree hollow. An individual Mountain Brushtail Possum may use up to 20 different hollows in 20 different years in any given year (Photo: Esther Beaton).

Large wire cage traps baited with apple are used to catch the Mountain Brushtail Possum. Green apples are used as the preferred bait – probably because the ethylene used to ripen “Granny Smith” apples is attractive to animals while they are foraging (perhaps because is resembles the smell of truffles which animals consume in several seasons of the year).

Large decaying logs provide important runways for animals like the Mountain Brushtail Possum – and assist them move through the dense ground cover that characterizes tall wet eucalypt forests.

 

Old growth stands of Mountain Ash forest such as this one are the tallest flowering plants in the world and they also support some of the highest known densities of the Mountain Brushtail possum