The case for welcoming possums into your backyard
THE COMMON brushtail (Trichosurus vulpecula) and its cousin the common ringtail (Pseudocheirus peregrinus) are considered annoying pests by many 21st-century Australian urbanites. And yet flourishing populations of brushtails and ringtails in and around many of our cities tell a remarkable story of survival when set against the backdrop of severe population decline and near-extinction for some of our possum species. Altered fire regimes; predation by cats, dogs and red foxes; road trauma; climate change; and habitat modification and fragmentation have all had an impact on possum survival.
Animals as diverse as Leadbeater’s possum, of Victoria’s central highland forests, and the diminutive mountain pygmy-possum – found in just three tiny pockets of the Australian Alps – remain under grave threat. In the south-western corner of Western Australia, the decline of the western ringtail possum was first noted as far back as the early 1900s.
Fox predation and land clearing ahead of agricultural development were to blame. And in recent decades, already restricted habitat south of Perth has been further degraded by rapid suburban encroachment, pushing this isolated species onto the endangered list.
Historically, possums formed part of many an Aboriginal meal and are often mentioned in early European exploration accounts. When French explorer Cyrille Laplace visited Sydney in 1831, he described Aboriginal women climbing for “lizards and possums into the highest tree-tops”, and holding out strips of possum meat to lure birds into their hands. Possums were also valued for their fur, sinew and spun fibre. Once Europeans arrived, however, the scale of Aboriginal subsistence hunting was quickly rendered insignificant – the possum wars had begun.
A ringtail possum. (Image Credit: Monkeystock/Shuttershock)
Down in numbers
THE VAST NUMBER OF possum skins exported historically from Australia is impossible to quantify. But it’s an indication of the size of the trade that in 1906 alone about 4 million brushtail and ringtail possum pelts were marketed
in London and New York. And, in the same year that The Gilgandra Weekly’s correspondent was bemoaning the raid on his smoked mutton, an estimated 900,000 brushtail possums and wallabies were shot just in Tasmania.
Commercial harvesting for the export fur and meat trade now only occurs on a small scale in Tasmania, where possums remain most abundant. Each year the take fluctuates significantly but in 2014–15, for example, commercial operators harvested about 20,000 brushtails. Many more are legally killed in Tasmania as a crop protection measure.
In pre-European times, the common brushtail possum was abundant through most of continental Australia, Tasmania and many offshore islands, but is now almost gone from much of the arid and semi-arid zones. Its decline in the dry interior runs parallel with the loss of other small mammals in what is termed the ‘critical weight range’ of 35g to 5.5kg. (Depending on where they’re found, adult male brushtails may weigh from 2 to 4.5kg.)
In contrast, common brushtails are thriving as alien freeloaders in New Zealand. They arrived in 1837 as a deliberate, and catastrophically misguided, introduction for the fur trade. The original industry of course failed, but 150 years later, and with a rampant appetite for New Zealand’s highly palatable forest vegetation, the possum population had reached an estimated peak of 60–70 million animals!
Aggressive control measures have now more than halved their numbers, but they are still a nightmare of a pest found in nearly all corners of the country.
Two common brushtail possums. (Image Credit: JJ Harrison)
We have to learn to share
Some Australian urbanites might delude themselves that they have a personal brushtail possum problem of trans-Tasman proportions. But it is unsurprising that these highly adaptable animals are right at home in an environment we have unwittingly fashioned to suit both us and them.
They will happily feast by night on everything from rosebuds and magnolia flowers to unattended pet food, and by day consider unprotected roof cavities the perfect city condos. But, although common brushtails and ringtails are now thriving in cities beyond the urban fringe and into their supposed strongholds among the open forests and woodlands of eastern Australia, these possum species are not doing as well as they once did. Again, habitat fragmentation and increased predation are two of the most likely causes of their demise.
Ecologist Clare McArthur from the University of Sydney’s School of Life and Environmental Sciences heads up a research group studying possum adaptation and behaviour changes due to urban encroachment on Sydney’s northern fringe at St Ives, one of several suburbs abutting the 15,000ha Ku-ring-gai Chase National Park.
At the interface between the natural possum habitat in the park and a typical, low-density leafy Sydney suburb, Clare’s group is gaining some interesting results. Surprisingly, she admits, at the outset the group had considerably more trouble trapping brushtails in the bush than in the city. “We just can’t find them!” she says. “But out at Ku-ring-gai we’ve got them all along the edge.”
It seems living in this environmental halfway house pays off for some brushtails. Many seem to be risk-takers and bold nocturnal foragers coming to houses in search of food. Their diet is more varied than the usual mainstay of eucalypt leaves, meaning despite threats from cars, cats and dogs, they probably enjoy a survival advantage. “If you are not prepared to take risks,” Clare says, “it’s difficult to live in cities.”
But, having eaten their usual native offerings, and perhaps raided a vegie patch or grazed on a few favourite exotic plants, a number of the study possums still prefer to retreat to the sanctuary of the bush by day, within the national park, where they’ll nest in natural tree hollows.
So, next time a battalion of brushtails marches across your roof in the middle of the night, or a ringtail prunes your garden to its liking, don’t feel annoyed and frustrated. Perhaps it’s time for you to pause, think laterally and consider installing a nesting box for your resident possum, abandon the roses and plant natives that both humans and possums can enjoy.
“We should feel privileged that we have these animals in our midst,” Clare says with conviction. “We find they’re disappearing in the bush, and yet people say, ‘Oh, they’re a problem in my roof.’ It’s not until they’re rare that someone suddenly cares.” And, to invoke Joni Mitchell and her 1970 song ‘Big Yellow Taxi’, “You don’t know what you’ve got till it’s gone”.