Genetic warfare is declared on Australia's dread cane toad

There they go, weaving and swerving across the highway, punching the air each time a cane toad is squashed beneath their tyres. It may seem brutal to outsiders, but there is no time for sentiment in the war against Australia's most wanted pest.

There they go, weaving and swerving across the highway, punching the air each time a cane toad is squashed beneath their tyres. It may seem brutal to outsiders, but there is no time for sentiment in the war against Australia's most wanted pest.

Cane toads have been marching across northern Australia since they were introduced to Queensland in 1935 in an effort to eradicate cane beetles from the sugar crop. Now they are closing in on Kakadu National Park, in the Northern Territory, and ecological Armageddon is predicted when they hop over the park borders.

The toads, which secrete a deadly toxin when threatened by predators, have already ravaged populations of native fauna in Queensland. Kookaburras, snakes, goannas - a type of sand monitor - and quolls - native cats - have all fallen victim. The toads' arrival in World Heritage-listed Kakadu, where the pristine wetlands swarm with wildlife, is a conservationist's nightmare.

As Kakadu's rangers grimly await the start of the wet season, which is expected to spell T-Day for the 14,000sq-mile park, scientists are embarking on a last-ditch offensive. The government has granted £400,000 to two laboratories for research into the use of gene technology to control the amphibians.

Dr Alex Hyatt, a zoologist at the Australian Animal Health Laboratory in Geelong, Victoria, said the aim was to engineer a gene to prevent toads from developing into sexually mature adults, and then use a virus to spread it among tadpoles. "Initially we will produce data to determine whether the idea has legs," he said.

The genetic weaponry could have a big impact on a species with a rampant libido. Females lay up to 40,000 eggs, and males copulate with anything that resembles a cane toad, including rocks, tree roots and shoes.

Previous research into biological methods of eradicating Bufo marinus was abandoned because of fears that native frogs would also be wiped out.

Originally from Venezuela, the toads were first released in Gordonvale, south of Cairns, where they ignored the cane beetles but ate virtually everything else, and began fanning out across the continent. Covering about 20 miles a year, they marched to the tip of Cape York and colonised the Northern Territory in the early 1980s. Enterprising toads turned up in Perth and Adelaide after hitching lifts on lorries.

They have also penetrated as far south as Port Macquarie, in New South Wales, raising fears of an onslaught on Sydney. Queensland, though, remains their principal habitat.

On rainy days, cane toads the size of dinner plates carpet the pavements; on warm evenings, they congregate in suburban backyards, stealing pet food and snacking on insects. Locals have tried every means of extermination. But spearing them with a garden fork merely displeases them, while thwacking them with a golf club serves only to let off steam. Even the nightly massacre on the roads makes a minuscule dent in an estimated population of 100 million.

Some Queenslanders are not averse to their warty neighbours. Children dress them up in doll's clothes; cane toad races are staged in Cairns pubs. Their skins are made into purses and handbags for tourists. Curiously, there are devotees who swear by the hallucinogenic powers of their venom. The 1970s saw an epidemic of toad-licking, and at least two Queensland dogs have been recorded as addicts.

The genetic research will not be completed for a decade, so the toads will have a free run in Kakadu. Mike Tyler, an associate professor of zoology at Flinders University in Adelaide, warns that they will have a catastrophic effect on the park. "Native species will die in great numbers and cane toads will become the most common form of life," he said. "Kakadu will never be the same again."