Extinction claims a furry friend

Photo by Nicholas Birks.
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Photo by Nicholas Birks.
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Dr Peter Hornsby inspects a nestbox.
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Monday, 2 April 2001

With native birds in serious decline in South Australia's Adelaide Hills, researchers have now declared a small but delightful native marsupial to be locally extinct there, sounding a grim warning about the environmental impact of human activities.

Extinction is forever, but local extinctions offer a second chance, since a species that vanishes from one area may persist in another. Still, they sound a pretty clear warning of environmental distress.

In the Adelaide Hills, close to South Australia's capital, researchers have noted a catastrophic reduction in native birds, with half the woodland species in decline. It seems that they are not alone.

"It is not only the birds that have gone from the Adelaide Hills," said Dr Peter Hornsby. "We have just completed our two-year search for brush-tailed phascogales in the southern Mount Lofty Ranges, without finding any. Furthermore, we also looked in the south-east, around Naracoorte, where the last official sighting occurred in 1967. It is a safe bet all the phascogales have gone; adding another species to South Australia's list of extinctions."

Dr Hornsby is a Visiting Research Fellow in Adelaide University's Department of Psychology. A specialist in the observational studies of behaviour, particularly of rock-wallabies, he has broadened his interests to include other native species. These include phascogales - small, carnivorous marsupials with large bushy tails - the Australian equivalent of tree shrews.

Dr Hornsby's work has come at an opportune time. "The whole of SA is at present being covered by a biodiversity survey," said Dr Hornsby. "It includes plants, mammals, birds, reptiles and some invertebrates," he said.

"The Department for Environment knew of our work, and are keen to incorporate our data into their survey because, while we have been looking for phascogales, we've effectively been sampling arboreal mammals," said Dr Hornsby.

Other species detected by the sampling methods included the native yellow-footed antechinus, bush rat and ring-tailed possum, while introduced black rats were also common.

The detection of these other species showed that Dr Hornsby was using effective techniques. These were hair tubes, well known to wildlife researchers, in which PVC tubes of a diameter suitable for phascogales are lined with double-sided adhesive tape.

Each tube is baited in its centre and fixed to a tree trunk. Any animal entering the tube leaves hairs attached to the tape, and species can be identified by microscopic examination of a single hair. Dr Hornsby used 900 of these hair tubes in his survey, after trialling them with captive animals.

"We spent a lot of time developing the design of the tubes with phascogales in Adelaide Zoo," said Dr Hornsby. "They helped, but in the end, the animals got very used to the trials, so we sent some tubes to Healesville sanctuary, and they worked there, so we are reasonably sure that the tubes we have been using will attract phascogales," he said.

Just to make sure, Dr Hornsby is about to 'ground truth' the hair tubes in parts of Victoria where wild phascogales remain. If the animals are detected there, it will confirm that they no longer exist in South Australia; already known as the mammalian extinction capital of the world because of the number of native mammals that the state has lost.

Some, such as the pig-footed bandicoot, toolache wallaby and hare wallabies are extinct everywhere. Others like the brush-tailed bettong and bilby have vanished from the state but still can be found in the wild in other parts of Australia. The loss of these mammals is a legacy of environmental pressures now threatening the birds of the Adelaide Hills.

"I don't think that there's any doubt that the decline of mammals and reptiles is a parallel to what is happening to birds," said Dr Hornsby. "It probably is a combination of several factors, including introduced predators such as the fox and cat, and loss of habitat," he said.

Dr Hornsby has added his voice to those calling for better management of native vegetation.

"Looking around the hills to-day, one can be led to the false conclusion there remains a reasonable amount of remnant woodland," said Dr Hornsby. " The critical feature overlooked is the nature of these remnants," he said. " When Europeans first arrived in South Australia, our hills were clothed with stringybark forests; well-spaced massive tall straight trees over 30 metres high with bases over two metres in diameter."

"These spectacular ancient trees had many hollows suitable for nest sites, and a wide, open, understorey," said Dr Hornsby. "Felling them has created instead a woodland of younger trees, many of which are coppice regrowth around the base of the older trees. This replacement woodland conspicuously lacks nesting-hollows, which phascogales need, and has a dense understorey," he said.

While the phascogale story is bleak, Dr Hornsby's work with rock-wallabies has had a more positive result. There has been national interest in surrogacy trials at Adelaide Zoo, in which young joeys of very rare brush-tailed rock-wallabies are transferred to the pouches of other wallaby species. These foster mothers rear them as their own, leaving the brush-tailed mothers free to bear additional young, and swell the numbers of the dangerously small population.

"The crucial factor is getting a newly born embryo at a critical time. That means knowing when these animals are going to mate and breed," said Dr Hornsby. "The conventional physiological way of doing this means that you've got to catch the animal and get urine or faecal samples," he said, "Whereas it is abundantly clear that when the female is coming into oestrus, the male knows that."

"One has only got to look at their behaviour to see when things are going to happen," said Dr Hornsby, "And this is where I was called in to help with the work at the zoo. It worked out quite well, because when I said this mating was taking place, it did take place," he said.

Dr Hornsby has also installed 100 nestboxes at premium sites for phascogales. The nestboxes, designed to suit the animals, were made by ROBIN, a Rotary project which manufactures nestboxes for community groups and researchers.

While the natural extinction of South Australia's phascogales now seems beyond doubt, it may not be permanent. "Paradoxically, if there were not phascogales in zoos, we wouldn't even know what they looked like," said Dr Hornsby," But we hope the next stage will be to give serious consideration to reintroducing phascogales into South Australia."

"That would require breeding colonies in the zoo," he said. "In that regard the zoo is an ideal place. Taking into account Adelaide Zoo's track record of breeding rare and endangered animals for reintroduction into the wild, this is a role we hope that the zoo would take on board."

But for that to be effective, the factors that have led to the decline of so many species will need to be reversed.

"A lot of our parks already have extensive fox baiting and control programs," said Dr Hornsby. "Cats are very difficult to control, but it's being looked into. The other aspect is the availability of appropriate habitat," he said.

"We can't grow forests in a short time, but what we can do is augment what we have got with the basic requirements of phascogales by putting up nestboxes in the stringy bark woodlands that we've got. Putting up nestboxes is going to help not only phascogales but all the other arboreal species, particularly birds, which are looking for nesting hollows that aren't there any more." Photos available at: /pr/media/photos/2001/ Contact: Dr Peter Hornsby, Phone: [61-8] 8303 5574 Fax: [61-8] 8303 3770 Mobile: 0428 817 568.

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