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Australia's endangered species. Part 2: Outlines some of the reasons for flora and fauna species becoming extinct during the last two centuries

CAROLYN COURT: Welcome to Earthworm, and the second program in a series of four, focusing on Australia's endangered species. This week, a look at some of the reasons for flora and fauna species becoming extinct during the last two centuries: how have Europeans managed to decimate Australia's unique mammal species, and how we are attempting to retrieve populations from extinction?

Since the settlement of Australia by Europeans, 20 species of mammals and birds and about 100 species of plants have become extinct. A further 72 species of mammals, birds, reptiles, frogs and fish, hundreds of species of invertebrates, and 209 plants are considered endangered and could become extinct within the next 10 to 20 years. Hundreds more species could be added to this list as potentially vulnerable.

Unlike the early European settlers, we now have an understanding of the vulnerability of our unique wildlife and an understanding of some of the threats to their survival, but we've also managed to add to that list of threats with our urban and industrial development, pollution and illegal smuggling of wildlife. One of the major causes of extinctions in Australia is the degradation of habitat. Reasons for habitat destruction have included clearing for agriculture, urban development, and for forestry and mining. Habitat has also become degraded by salination, erosion, grazing by introduced herbivores, by the presence of environmental weeds, and by the use of modern fire regimes, instead of the Aboriginal mosaic burning method.

Australia also has a large number of introduced animals and plants that have caused or have the potential to cause extinction of native species. Alan Newsome, Senior Research Scientist with the CSIRO's Department of Wildlife and Ecology, has observed the effect of feral animals on Australia's flora and fauna for the last few decades.

ALAN NEWSOME: There are two ways of thinking about it: one is the damage to habitat and the other is actual predation. If you think about habitats, buffalo and pigs in the wet lands, really make a mess of them. If you think about predation, we've got the European fox and the feral cat as the major problems that we're confronting at the moment.

I want to go back just one step - the rabbit is the other issue, as well as sheep and cattle in the inland. Think about 100 years ago, with the pioneering Europeans introducing sheep and cattle to a virgin land. We know that there were grasslands from the explorers' words. We know that there were, in these grasslands, living in little hutches, just like hares tend to, there were bandicoots. We know there were warrens with burrowing wallabies in them - the bettongias - but the rabbits usurped those warrens. The cattle, the sheep, the feral goats, the rabbits, ate the grass that sheltered them, so they were left homeless in one sense. But we also know that in the inland at least, where most of the problems have occurred for extinctions and vulnerability of the marsupial fauna, and some of the rodent fauna - we often forget them - we know that those animals were present in the 1930s. About the 1930s, the fox arrived in central Australia. The rabbit was there about 1900 and reached its northern limit, and the biggest problems have occurred since then.

CAROLYN COURT: Well, where have foxes wreaked the most havoc?

ALAN NEWSOME: You've got to think of the fox and the rabbit virtually as a complex. When I first went to central Australia as a biologist, well, too long ago, 30 years ago, I knew where animals had been found up to 20 and 50 years earlier. They weren't there, but I found some of these animals - a desert hare wallaby - I found some of them out in the Tanami Desert. I found rabbit-eared bandicoot, which was extinct further south, out in the Tanami Desert. And it seemed to me at that stage, that this was because they were beyond the cattle country. The cattle were on the best of the lands around the Macdonald Ranges, and this is where the animals used to be found, but weren't found there now. Well, what's now quite plain is that they were also on the limit of the extent of the rabbit in Australia and, therefore, the fox. The fox and rabbit are not in northern Australia and the tropical lands. They get up into the Gulf of Carpentaria, but that's a tiny arid patch in through there. Basically, they're .. you think of where the Tropic of Capricornia is, from there south, that's the domain of the rabbit and the fox; it's also the domain of the sheep, and the cattle tend to be further north.

So, we can now see with hindsight that it was this combination of the rabbit competing for food, excluding animals from their burrows - the rabbit-eared bandicoot was a burrower. The rabbits take over their burrows. This burrowing bettongia - they take over their burrows. And think of the competition for food during a drought. Everything is in trouble. Rabbit is far more numerous than the marsupials that were living there, and so the marsupials start to lose. Then think of the foxes living on rabbits; that's their main diet. When the rabbit numbers collapse, the foxes are going to be eating anything. And so the vulnerability of the marsupials, as far as we can tell, is likely to be greatest under those circumstances. But when the numbers of any prey become very low, then they're always vulnerable, and that's the state of play on Australia today.

CAROLYN COURT: Alan Newsome. Some islands around Australia contain the only surviving populations of certain native fauna species, and have as such been havens. But other islands that feral animals have made their way onto, have witnessed species coming frighteningly close to extinction. John Hicks from the Australian National Parks and Wildlife Service, who worked for a number of years on Norfolk Island, tells of the experience of rabbits on nearby Phillip Island.

JOHN HICKS: Phillip Island which is just near Norfolk Island in the South Pacific, was once lushly covered with subtropical rainforest. Rabbits, goats and pigs were introduced late in the 18th century and early in the 19th century, and over the next 100 years they pretty well wiped out the vegetation. By the turn of the 20th century, it was an eroded landscape, something like a colourful moonscape, I suppose would be the best description of it. And the island was losing soil at an average rate of between two to four centimetres a year, and the odd tree that was left on the island was perched, suspended by this network of roots, and you could see that the depth of soil that had been lost through the damage by these introduced grazers. It certainly had a huge impact on the land birds that were there. The island was still very valuable for nesting sea birds, which weren't so dependent on the vegetation cover, but certainly for the land birds, a huge impact, and for the flora too, a huge impact. There are a number of endangered plant species in the Norfolk Island group and some of those are restricted to Phillip Island. The Phillip Island hibiscus, for instance, was down to two relic shrubs and they were at the mercy of the rabbits, and there was no regeneration occurring, and the bushes that were there, were probably 150 years old; so, it was really at peril.

CAROLYN COURT: What sort of action was taken to remove the rabbits from the island?

JOHN HICKS: Well, there was an experimental program undertaken from 1979 to 1982, which demonstrated the impact of the rabbits, and then from 1982 to 1986, a removal program was conducted. The island is just 200 hectares in extent, but it's incredibly steep and highly dissected topography. And the removal program was very difficult, and it involved innovative techniques like firing arrows from a bow, the tip of the arrow containing fleas that were infected with the myxomatosis virus to inaccessible parts of the island, and it involved some poisoning and it involved some trapping; it involved some shooting. And by 1986 we got what we thought was the last rabbit, and we got the last rabbit again in 1988.

CAROLYN COURT: And what effect has that had on the island? Is it regenerating?

JOHN HICKS: Well, it's been really quite exciting. In the last stages of the rabbit eradication program, we rediscovered a plant that we previously thought was extinct - a birchelon juliana(?). It apparently survived on one of the more remote ledges, and once the rabbit grazing pressure was removed, it started to regenerate on the main part of the island. So that's one plant that we thought extinct, came back to life. Another grass that had been last seen around the turn of the century, turned up again, too, so that was another recovery of something that we thought we'd lost, and the Phillip Island hibiscus started regenerating too. So, from the plant point of view, it was just terrific. We were getting some things that we thought had gone, have come back.

CAROLYN COURT: So can islands play a particular role in conserving endangered species?

JOHN HICKS: Islands are quite often the source of very interesting biota. Islands typically have a large number of endemic species, and Phillip Island and Norfolk Island are no exception. There are some 40 plants that are found in that island group and nowhere else in the world. If they're not conserved there in the wild, they won't be conserved. So, they certainly do have a major part to play in maintaining biodiversity.

CAROLYN COURT: John Hicks from the Australian National Parks and Wildlife Service. One group of native fauna has been badly hit by extinction. Ninety per cent of all our mammal species with body weights between 35 grams and 5.5 kilos, are either extinct or endangered. These extinctions have taken place mainly in Australia's inland arid zone, for a range of reasons, including altered fire regimes and feral animals. Some of the marsupial species that used to live in central Australia, now survive in the south-west of Western Australia. One of the more well-known of these is the attractive faunal emblem of Western Australia, the numbat, now only found in parts of the Jarrah forest and on some reserves in the wheat belt, to the east of this forest.

There's an estimated 2,000 - 3,000 numbats left. Habitat degradation and feral animals have been and remain the main threats to numbats. Tony Friend, Senior Wildlife Officer with the Department of Conservation and Land Management in Western Australia, who's been working on a captive breeding program for numbats.

TONY FRIEND: The strongest influence that's likely to push the numbat to extinction, is predation by the introduced fox. There have been two times when there have been major declines in numbat numbers, and one was about the 1930s and '40s, when foxes first reached Western Australia, and the other was in the 1970s, when fox numbers built up after 1080 baiting of rabbits ceased. Since then, we've done an experiment where foxes are removed by poisoning from one area of numbat habitat, and not from another, and then the numbers of numbats in each of those has been traced or followed, monitored, and we've found that there was a dramatic increase in the number of numbats in the area that was baited.

And so the implication is that foxes are taking enough numbats to actually reduce the population and, in some cases, apparently, push it to extinction; so that the most important and the most urgent management procedure is reducing fox densities, and this has been shown also to enhance the survival of a whole range of medium-sized mammals. Some of the other endangered species that we have in the south-west, just hanging on, like the brush-tail bettong and the tama wallaby, have had their numbers increased on several reserves, just by the simple procedure of baiting foxes regularly.

CAROLYN COURT: The National Endangered Species Program has put a large amount of its resources into fox control, recognising foxes as one of the greatest threats to our unique mammals. 1080 baiting is currently used in Western Australia for fox control because native fauna in this State are immune to the poison, and the resulting flourishing of native animals shows how much of an effect foxes are having on populations.

TONY FRIEND: We're lucky here in that we can use 1080 to control introduced animals. Because of the presence of sodium monofluoroacetate in some of the .. what are called poison plants, the gastrolobiums, this has resulted in most of the native fauna being highly tolerant to 1080 poison which is monofluoroacetic acid - a very closely related compound. So, we've been able to use 1080 as well as for control of rabbits and - I guess rabbits and foxes are the main animals - pigs as well. We've been able to concoct a bait which is lethal to foxes but is not taken by many other animals, and those that do take it, will not be affected by it.

CAROLYN COURT: Tony Friend. The crudeness of this method of fox control and the need for fox control in other States, has led to concerted efforts by researchers to attempt to find a better solution. Alan Newsome.

ALAN NEWSOME: The use of toxins, poisons of any kind, is not very friendly in an environmental sense. It's messy. You continue to have to put out the baits. If you want to control the animals, you've got to be at it all the time - very, very expensive. And the division within CSIRO has been thinking about a novel way of doing this and, indeed, has embarked upon this. The idea that Dr Tyndale-Biscoe - Hugh Tyndale-Biscoe - has in the division, is of interfering with fertility. We're aware of how this works in humans, but you have to take a pill. How do you make foxes take a pill? How do you make rabbits take a pill? Well, the technique that's in mind is this: there are certain proteins in the reproductive process - let's think of the egg of a mammal, which is very tiny in a mammal, microscopic. But surrounding it is not quite a shell, but there is a special kind of coating on the outside. Now this coating is made up of special chemicals. Once the specific protein has been identified in that, then that protein can be used in the laboratory to make many, many more of it; cloned in other words. And then can be inserted into the rabbit is the one we can think about most clearly because the myxoma virus already exists in Australia, and there are very mild strains of myxoma virus that hardly make the rabbit sick, others kill them, but others are very, very mild.

What the division has succeeded in doing is working out within the myxoma virus where in the genetic sequence something can be inserted. Now that something can be the protein that actually exists on the coating of the egg of the rabbit. Once injected into the rabbit, artificially in the laboratory - by mosquitoes carrying myxoma around in the field - once injected in, then the rabbit will make antibodies to its own protein and, therefore, render itself infertile. Now that's a very, very potted history, and it's a long way between the start and the finish of such a thing and, indeed, you just don't release these things upon the environment, as you well know.

There's a very tight screening for all of these and, indeed, we wouldn't do that initially anyhow. You need to know so much about the rabbit's ecology and the spread of a virus in order to see that it does, in fact, infect sufficient numbers. So, first up, they'd be using a marker gene, something that can be detected much more readily, to find out just the rate of spread, but that's a long way down the line - five, six, maybe 10 years down the line. The important point I want to stress is that this initiative which is a first, in fact, for Australia, and to think of it in this sense. There's an experiment that's been shown for mice abroad that, in fact, you can do this in the laboratory. What we are going to endeavour to do is make this work in the field. If we can make it work for the rabbit, we can make it work for the fox and, in the long run, we should be able to make it work for any of these feral animals we've been talking about.

CAROLYN COURT: Another project to increase numbat numbers has been captive breeding. Tony Friend talks about the techniques that are being used.

TONY FRIEND: There were several things had to be sorted out before we could get numbats breeding on a regular basis, and I guess it's true to say that we're still sorting some of these out. The main breakthroughs that we were able to make were being able to feed the numbats, firstly. Numbats eat termites. They eat some ants in the wild, but basically they search for termites, and that's what is their staple diet. We had to be able to provide 15,000 to 20,000 live termites per numbat, per day. We managed to do this while we had two numbats in captivity, but once they bred and the young were weaned, it was impossible, just impossible to provide enough termites. The numbers just became too high and we had to find an artificial diet which we could replace the termites with, which would still maintain the animals in health and allow them to breed. The diet we ended up using was one developed for echidnas, for young echidnas, and that had been shown to support them, and they were able to grow more rapidly than they could on termites. So we tried this with the numbats and, after a few days, they found that it wasn't so bad, and we were able to test that diet and found that the animals could breed on it.

The second breakthrough was to be able to keep tabs on the oestrous cycle of the female, so that we didn't put the males and the females in together too early. In the wild, males and females live separately. Numbats are solitary animals, and they only really come together at the breeding season and, at that stage, the female is able to escape from or keep the male away when she's not in oestrous. Obviously, if you put them in a cage together, it's a stressed situation if the female is not ready. So we had to be able to tell when oestrous was coming, and this was just a matter of applying techniques that had been developed for dasyuridaes, which are closely related marsupials. You have to collect urine daily and examine it under a microscope, and the presence of epithelial cells in the urine shows that the animal has come into oestrousis. So, over a couple of breeding seasons, we got this down to a fine art and were able to put males in on the day that the females were ready to breed, and away they went.

CAROLYN COURT: What's the rate of success been?

TONY FRIEND: We've actually had 19 young born so far in the program; that's over about five years. That's a fairly slow rate. We've only had colonies of about .. well, between six and 12 animals at most stages. I have great hopes for this breeding season coming up in summer this year, that we'll be able to increase the rate of success and just start churning them out.

CAROLYN COURT: What further steps then will be needed to be taken to ensure their survival, once they've been bred?

TONY FRIEND: Well, in captitivity, there's no real problem, but obviously we need to be able to use the captive breeding program to enhance the wild populations or at least to set up new ones, and that's the other major part of the program: the re-establishment of populations in the wild. And as well as using captive-bred animals which we've done on a couple of occasions - released captive bred animals into the wild and then traced their progress by monitoring them with radio collars - we've also used wild animals from the population at Dryandra forest, which has been increasing since fox baiting regimes have been imposed. So using wild and captive bred animals, we've set up two new populations now. The first, which was established in 1985 on Boyager Nature Reserve, is flourishing. And on the reserve where the numbat was completely extinct, you can now drive around the roads and see numbats in the bush or running across the road.

CAROLYN COURT: It's one thing being able to breed numbats successfully, and another issue to be able to provide appropriate habitat for them to survive in. Farmers and other members of the community have played an important role in helping regenerate habitat.

TONY FRIEND: One remarkable story, I suppose, was the effort that was actually co-ordinated by men of the trees in the planting of the first corridor between two blocks of Dryandra forest, and they're two of the landholders who just happen to have adjacent land which was able to form a corridor, just freely gave their land, or allowed it to be replanted, gave assistance with the fencing, so that now there's a corridor of about 300 metres long and 100 metres wide linking two of the blocks of prime numbat habitat. The result of that has been that we're now seeing numbat diggings in the smaller block, which has now been linked to the large block where there were no numbats before.

CAROLYN COURT: Tony Friend, Senior Wildlife Officer with the Department of Conservation and Land Management in Western Australia. Numbats are now receiving quite a bit of attention and deservedly so, but what about less cute and furry animals? Let's take, for instance, the Tasmanian fish known by its scientific name `galaxias pedderensus'. This fish had the misfortune to live in Lake Pedder. It now lives in the inundated Serpentine River, but in very small numbers. Wayne Fulton of the Inland Fisheries Commission, is researching ways to save this unglamorous creature from extinction.

WAYNE FULTON: It's not a very dramatic looking fish. It's a fairly small, elongated fish, probably up to about 10-12 centimetres long, with dark green to brown markings on the back.

CAROLYN COURT: And how small a population is left?

WAYNE FULTON: There's only a very small population left. We've been looking round about 100 or so streams over the last two years, and we've managed to find about 10 to 15 specimens, that's all.

CAROLYN COURT: What sort of factors have led to this decline in numbers, then?

WAYNE FULTON: It's very difficult to say. If we knew that, I think we'd probably be part way there to helping it. But certainly introduced trout have had some effect, but I don't think they're the major influence. I think more recently there's been an influx of a native fish species which is getting more into its range, and I think is probably out-competing it. After the flooding of Lake Pedder, the population really expanded considerably in the new lake, and it was very, very common. But then in the early '80s, it commenced the decline and that seems to be associated with the influx of this other native fish species.

CAROLYN COURT: What management do you think is needed to help ensure that the species survives?

WAYNE FULTON: Well, it's to such a stage now, I think the only viable way we can save the fish is to translocate it to a safe habitat. We've looked at the streams that it's in and there's no way we can prevent any outside influences on those, so we'd have to find a habitat that hasn't got other fish in it, and move it to there. We're trying captive breeding at the moment. It's proved quite difficult to keep in captivity, and I guess that's one of things that's made it vulnerable to extinction. But we've got a large tank set up at our hatcheries at the salmon ponds, in which we've got a few specimens at the moment, hoping that we can get something going there.

CAROLYN COURT: What do you think is the importance of preserving a fairly humble fish species like this one?

WAYNE FULTON: Yes, that's a question that's quite often asked, I think, with all fauna. I think it's just we really need to conserve diversity in nature. I don't think it's for us to determine which species is more important than another. A species by definition is unique. It is part of our heritage and part of the diversity of nature.

CAROLYN COURT: Wayne Fulton from the Inland Fisheries Commission.