Exclusion fencing vital to relocation success
The successful reintroduction of brushtail possums to the Wheatbelt has been attributed to a habitat free from foxes, feral cats and other possums, with plenty of tree hollows and rock crevices.
The possums (Trichosurus vulpecula) were released in 2008 and 2010 into the Wadderin Sanctuary, which is surrounded by a 9km barrier fence that allows the possums out but makes it difficult for animals to enter.
Wildlife Research Management principal research scientist Jeff Short says four possums were released in 2008 and five in 2010, resulting in about 20–30 possums living within the sanctuary and others settling outside the predator-free zone.
"A lot of the young recruits would go over the fence and try and establish ranges on the outside," he says.
There have been at least 14 attempts to translocate brushtail possums in Australia, but few have been successful.
One of the problems is the social structure of possums makes it difficult to introduce new migrants to existing populations, Dr Short says.
"They have this interesting social system where the females procure a large home range to allow their daughters to settle around them," he says.
"It's sort of a matriarchal society… the females will actually discourage other unrelated females from settling nearby."
Foxes, feral cats and burrowing echidnas
Dr Short says introduced animals have devastated Australian mammal populations and exclusion fencing is becoming more and more important in conservation projects, despite the ongoing maintenance required.
"The benefit of that is that it targets both foxes and feral cats," he says.
"We haven't still really gotten to the point of successfully controlling feral cats on a broad scale, in fact we struggle even on a relatively small scale."
At Wadderin, two retired farmers have taken on the role of regularly inspecting and maintaining the fence, Dr Short says.
"One of the key problem species for us has been echidnas, which have the habit of trying to burrow under the fence," he says.
"They get their nose under the skirt of the fence and push through, and create holes that other species can come in through."
Dr Short says the availability of shelter for the possums contributed to their successful reintroduction at Wadderin Sanctuary.
"The habitat quality itself was quite good, with old growth trees, lots of hollows and rocky areas with rocky caves, so there was plenty of shelter sites," he says.
The project is documented in a paper published this month in Australian Mammalogy.