THE AUSTRALIAN (Sydney) 09 August 05 Sentenced to death (Asa Wahlquist)
Death for a native animal that eats a cane toad is shocking and quick. Wildlife scientist Meri Oakwood says it starts convulsing, its eyes glaze and it tries to eat sand or dirt to get rid of the horrible taste in its mouth. Within a few minutes, it's dead.
Cane toad toxin leaves distinct signs. The animal that ingests it gets bright red lips, irritated by the toxins. It has nose and ear bleeds and internal bleeding, Oakwood says.
Every stage of the cane toad's life - from tadpole to adult - is poisonous. When they are disturbed the adults exude a milky poison from glands on their shoulders that causes heart failure in animals that eat it.
Cane toads were introduced to Australia in June 1935 to control several beetle pests of sugar cane. They quickly bred in captivity and on August 18, 1935 they were released into cane fields at Gordonvale, near Cairns.
Those 101 toads have multiplied into hundreds of millions today, their numbers growing inexorably as they spread. They've been found as far south as Port Macquarie, on the mid-north coast of NSW. They are crawling across the Northern Territory, closing in on Darwin. Sixteen have been found in the botanical gardens, 10 years ahead of when experts predicted they would infiltrate Darwin. A line of traps has been set, near the Northern Territory-Western Australia border, and checks are made at WA travel stops for hitchhiking toads. Cane toads have also been found in fruit crates in Sydney and shoes in WA.
To try to halt the invasion the WA Government last week gave $500,000 to the community-based Stop The Toad Foundation, money that was matched by the commonwealth. The only organised method of killing cane toads is to trap them, usually by luring them through a one-way entrance into a trap equipped with lights that attract insects, and water. Toads live happily in these traps - locals jokingly call them cane toad motels - until someone picks up every toad, puts them in a plastic bag and kills them by gassing with carbon dioxide.
A recent report for the National Cane Toad Taskforce dismisses trapping as a control, saying the long-term benefits are likely to be negligible. It found that, for a population of one million toads, 330,000 would have to be removed each year to have an impact. It describes the toad as a highly invasive species that has colonised substantial areas of the Australian continent, occupying the habitats of many native species.
Given that cane toads mate twice a year and a female can lay up to 35,000 eggs at a time, what's needed is a biological solution. Senior CSIRO scientist, Tony Robinson, says that because cane toads are an environmental, not an agricultural, problem, funding to eradicate them has been in short supply. "If it is not a pest or an invasive species that affects agriculture, agriculture is not going to put money into that," Robinson says.
The Department of Environment and Heritage last week put $3 million, in addition to an earlier $5 million, into cane toad research, as well as contributions from the states to find a biological solution.
"A bio-control approach of some sort is probably the only way that we can go," Robinson says. The CSIRO has been investigating biological controls since 1986. Studies of cane toads in their native Venezuela found viruses which unfortunately turned out to be common to Australian frogs. Research is now focused on producing a genetically modified organism, specific to the cane toad, that would target metamorphosis - when the toad is most vulnerable - and interrupt the toad's growth cycle.
"There are a whole lot of proteins that are produced in the adult phase that are not produced in the tadpole phase," Robinson says. "Exposing tadpoles to those proteins could affect their metamorphosis."
While researchers are looking at delivering the interrupter genes by a ranavirus, ranaviruses are not specific to the cane toad. "Another part of our project is to look for host-specific viruses," Robinson says.
"We have isolated 15 new genes that we are now testing."
Research has so far been funded on a year-to-year basis: the $3 million announced last week will guarantee funding for the next three years. But Robinson predicts it will take at least another five years before they have a cane toad bio-control they can test in the field. Robinson is also interested in looking at native animals that, according to anecdotal evidence, have developed some resistance.
He wants to compare animals in Queensland with long exposure to cane toads, to their toad-free WA relatives. "With new molecular techniques we could do that quickly," Robinson says.
Despite the clamour over the spread of the cane toad, there is a surprising dearth of research on its environmental impact. Graeme Sawyer is the Darwin-based co-ordinator of Frogwatch which runs regular updates of the latest cane toad sighting in the Territory. "The official experts predicted cane toads were going to get to Darwin in 2015," Sawyer says. "They were out by 10 years. We are getting increasing outbreaks of 'hitchhiker' toads in and around Darwin in the past couple of months, and the main invasion front is about 30 to 40km away."
Sawyer says cane toads damage the environment in three ways: the adults poison predator animals such as goannas; smaller animals such as frill-necked lizards die from eating toadlets; and as the population of cane toads builds, they overwhelm the ecosystem, consuming resources and taking shelter and breeding spots from native animals.
Oakwood has undertaken one of the few studies that first collected baseline data of what happens before and after the cane toad arrives, by studying quolls in Kakadu National Park.
"We were concerned that these vertebrate predators were likely to take cane toads, so we thought they were potentially at risk," Oakwood says.
The results were shocking. At one site, in southern Kakadu, the quolls became extinct within one year of the cane toads arriving. In northern Kakadu they are clinging on. "We only had three animals left in April - we had 45 - so we are very close to extinction in our northern site now," she says.
Oakwood points out there are many native predators, including the antechinus, birds of prey and snakes, that could suffer population falls due to poisoning by cane toads. There are indications some goannas have learned to avoid toads, while some birds flip the toads over and attack the abdomen, avoiding the venomous shoulders.
But Oakwood is pessimistic. The wider conclusion for native wildlife is doom and gloom. "The cane toad is going to go right across to the Kimberley. It is going to affect a lot of our native predators," she says.
Unless it can be eventually stopped.
Sentenced to death