Cane toad war turns into battle of sexes

SYDNEY - The much despised cane toad, one of Australia's most destructive pests, may be about to meet its match - a daughterless gene which would ensure female toads could only produce male tadpoles.

The gene is being developed by scientists in Queensland, the state which was first overrun by Bufo marinus after it was introduced from Hawaii in the 1930s in a failed attempt to control sugar cane beetles.

If successful, it would ensure that cane toads would breed themselves out of existence in Australia, with millions of lonely males eventually dwindling to extinction.

Impeding the toads' breeding cycle is particularly effective in combating the species' inexorable expansion - because a female toad can lay up to 30,000 eggs at a time.

Developmental biologist Peter Koopman, of Queensland University, unveiled the gene project at a national cane toad conference in Brisbane.

He said it was much safer than other strategies.

"There are no poisons, toxins or viruses being released into the environment. The possibility of this spreading to other species is zero, Koopman said.

"We're looking at letting them loose in two to five years time. It's the Rolls-Royce of genetic strategies."

Once released into the wild, scientists hope that the genetically altered toads would mate with as many ordinary toads as possible, thus spreading the gene.

Since being introduced to Australia, cane toads have proved remarkably resilient, spreading south into New South Wales and west into the Northern Territory, where they have invaded World Heritage-listed Kakadu national park.

Toxic glands in their skin are lethal to animals which eat them, including crocodiles, goanna lizards and quolls, rare marsupial predators about the size of a cat. Even the toads eggs and tadpoles are poisonous.

They are almost universally despised by Australians, who deliberately swerve their cars to squash them and even use them for golf practice.

"This may not be the silver bullet," Koopman said. "No single strategy is going to be completely effective so we have to throw as many things as we can at this pest."

Despite the best efforts of Australians who organise toad musters to round up and kill the amphibians, they are expected in the next two years to cross from the Northern Territory into Western Australia.

They are spreading at a rate of about 60km a year. A recent estimate put the population at 200 million.