Australia Gains a Fish, Loses a Mammal

By Cat Lazaroff

ADELAIDE, Australia, April 2, 2001 (ENS) - Australia's largest river, the Murray, has gained a new fish species - the Yarra pygmy perch - offering a bright spot in the river's legacy of pollution and dwindling biodiversity. But in other parts of the nation, species like the tiny brush tailed phascogale and dozens of woodland birds may be vanishing forever.

With the many problems besetting the Murray, tales of species decline and extinction are expected. Discovering a new species is not.


The Yarra pygmy perch, newly discovered in the Murray-Darling Basin (All photos courtesy Adelaide University Media)
"We were doing some survey work at Lake Alexandrina," said Michael Hammer, an honors student in Adelaide University's Department of Environmental Biology. "A volunteer was helping me out and found what we thought was a juvenile pygmy perch. Later we ran genetic tests to see if it was different from other local populations of pygmy perch, and it turned out to be a totally different species."

Hammer is studying the southern pygmy perch, a locally endangered species now found only in selected spots in the Mount Lofty Ranges. The new species turned out to be a Yarra pygmy perch, apparently far from home.

"As its name suggests, it was originally found in the Yarra, but it's distributed from Melbourne up to Bool Lagoon in South Australia, so it's a fair way from the Murray," said Hammer. "No one's ever identified it in the Murray-Darling Basin before. It's definitely a new species for the area, so we're trying to work out if it's a genetically distinct population in the species, or a new species altogether."

The Yarra pygmy perch is designated nationally as potentially threatened, which means it is still common in certain regions but overall has suffered a large decrease in its range. The discovery of this population has significant implications for the management of the region.

"We need to map its range as a first step," said Hammer. "We need to find out what its habitat requirements are in order to secure that habitat, and also look at forming refuge populations in case of catastrophe or extinction in the wild."


Honors student Michael Hammer studies a gel to identify the DNA from different fish species
Pygmy perch reach a maximum size of eight centimeters (just over three inches), and are threatened by several introduced fish species, such as mosquito fish, redfin and trout.

Hammer will return to the region to try to discover more specimens, and perhaps more populations, of this addition to South Australian wildlife.

"There are really only 10 or 11 local native fish species capable of completing their lifecycle in fresh water, with about 26 species in the whole Murray-Darling Basin," said Hammer, "so the finding represents a significant boost to local biodiversity."

"It gives you hope that some of the fish that we've lost might still be around," Hammer added. "There are three or four fish that are believed to be extinct, but they could still be around; you never know."


In other Australian regions, the news is not as encouraging.

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. And the birds are not alone.


A brush tailed phascogale, believed to be extinct in South Australia
"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 southeast, 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 at Adelaide University's Department of Psychology. A specialist in the observational studies of behavior, 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.

The Australian Department for Environment is currently undergoing a complete biodiversity survey of South Australia, covering plants, mammals, birds, reptiles and some invertebrates, Hornsby 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 Hornsby.

Hornsby and his colleagues use hair tubes to sample the mammalian life of a region. Hair tubes are PVC pipes lined with double sided adhesive tape.

Each tube is baited in its center 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.


Phascogales, never common, are now known mostly from zoos
"We spent a lot of time developing the design of the tubes with phascogales in Adelaide Zoo," said 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."

Just to make sure, Dr Hornsby is about to test 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 Hornsby. "It probably is a combination of several factors, including introduced predators such as the fox and cat, and loss of habitat."

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 Hornsby. "The critical feature overlooked is the nature of these remnants. When Europeans first arrived in South Australia, our hills were clothed with stringybark forests; well spaced massive tall straight trees over 30 meters (98 feet) high with bases over two meters (six feet) in diameter."

"These spectacular ancient trees had many hollows suitable for nest sites, and a wide, open, understorey," said 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."


Dr Peter Hornsby inspects a nestbox designed for small mammals like the phascogale
Hornsby has 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 Hornsby," But we hope the next stage will be to give serious consideration to reintroducing phascogales into South Australia."

"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," he noted. "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."