Mountain Pygmy-possums are in trouble. Being a Mountain Pygmy-possum in this millennium was bound to be risky. Dean Heinze, Victorian possum researcher, and Dr Linda Broome estimated that before 2000 there were about 1800 adult female and 600 adult male Mountain Pygmy-possums in existence, in the world, total.
Until December 2010, it was thought that Mountain Pygmy-possums only lived above the winter snowline (about 1500 m) in alpine and subalpine areas of southern NSW and north-east Victoria. At this altitude, the snowline is receding rapidly because of global warming. Snow provides an insulating doona over hibernating possums and is important in the co-ordination of the possum’s annual cycle with food availability and appears to restrict potential competitors and predators.
The main habitat of the possum are piles of rocks formed by periglacial activity below mountain peaks (boulder fields) and associated shrubby heathland. The rocks attract millions of migratory bogong moths that provide the main food for possums in spring and help protect the possums from the attentions of feral predators. Possums also forage outside the rocks in the surrounding heathland for nectar, beetles, caterpillars, spiders, seeds and fruits. It is likely that before Europeans introduced red foxes and feral cats to the alpine area, possums were much more abundant throughout the alpine and sub alpine heathlands than they are now.
Due to the coincidence of deep snow, south easterly aspects which retain snow longest, and deep piles of rocks, most of the best possum habitats are in ski resorts. The numbers of Mountain Pygmy-possums in the ski resorts in Kosciuszko National park have declined substantially over the last ten years from an average of 30 females at Mt Blue Cow before 2000 to only one last year. At Charlotte Pass the average has dropped from 26 pre-1997 to less than half this number since 2000.
The reasons for these declines are not clear, but scientists have noticed large numbers of feral cats around the resort areas, as well as foxes. It is possible that the numbers of these predators have increased in recent years due to a long run of years with low snow cover. The other possibility is that the possums are more susceptible to predation because in some years the snow appears to be melting before the arrival of bogong moths in the boulder fields, prompting the possums to forage outside the shelter of the rocks in the surrounding heathland.
Control of foxes is relatively easy and was commenced in the late 1990’s but cat control was not started until 2002. Eighty two feral cats were removed from Perisher-Blue and nine from Charlotte Pass ski resorts during winter cage trapping between 2002-2008. However, possum populations are still in decline in the resort areas, cats are frequently seen, and it is not known how many cats remain in these precincts and what proportion of the cat population is not trappable in cage traps.
This project aims to assess the abundance of feral cats throughout the distribution of the Mountain Pygmy-possum in NSW, to develop methods of monitoring cat numbers so that scientists can determine how effective the control methods are and develop better control methods as needed.
Beginning in March 2009, scientists have been using motion-sensitive infra-red cameras as a way of detecting the presence of cats. So far, scientists have tried placing clusters of ten of these cameras within the resort areas and ten outside the resorts for several weeks at a time to examine relative densities of cats. Scientists are also trialling the effectiveness of food and olfactory lures to attract the cats close to the cameras, to have their photos taken. The cameras can later be replaced by traps or poison baits. The lures, obtained from a trapping supplier in Queensland, have enticing names ‘Cat Snatch’, “Cats me Dead’ and ‘Cat Call’. However, so far it seems that the feral cats (being cats) walk disdainfully by the lures and only the foxes spend time sniffing at them. Scientists even have film footage of foxes trying to demolish the feeders containing the cat food.
Scientists have collected the cameras for the winter after they became buried in snow during the early fall in May, which melted fortunately for us but not the possums. However, scientists have purchased an additional 20 cameras and will continue the trials this spring. Cats prefer live prey and are attracted by novel items and movement, the old curiosity killed the pieces of tinsel on bushes near the cameras. So if you visit Kosciuszko National Park this summer, beware about making comments on apparent Christmas trees. Scientists already have some amusing footage of curious humans!
Another way to find evidence of predators and what they are eating is to look for their scats (faeces). It is frequently difficult to distinguish cat scats from fox scats by appearance. However, cats are more likely to conceal their scats and several cat scats have been already been found in Mountain Pygmy-possum habitat outside ski resorts, under the cover of rocks or Mountain Plum-pine shrubs. Searches for predator scats will be conducted in areas of pygmy-possum habitat and sent to an expert ‘scatologist’, Barbara Triggs, for identification by hair analysis (detection of cat, fox or dog grooming hairs) and prey species.
The Foundation for National Parks and Wildlife is supporting this project and the scientists wish to thank all the supporters who contributed to the call for funding. The project continued through the summer of 2009-10 and scientists are hopeful that more effective cat control methods will help the Mountain Pygmy-possum hang on in its diminishing snowy environment, long enough for humans to reverse the effects of climate change.
