Cane toads close in on Australia's wildlife reserves

A biological weapon has backfired, GREG ANSLEY reports.

CANBERRA - They were chilling finds.

A householder in the small town of Menai, south of Sydney, opened her door this week to find a juvenile cane toad sitting on the front porch, probably after hitchhiking on a truck from Queensland.

Menai is a dangerously short hop from the Royal National Park, the world's second-oldest national park and home to hundreds of species of birds, mammals, reptiles and amphibians, most of them vulnerable to Australia's most odious and unwanted migrant.

The area is also uncomfortably within the toad's potential habitat, one whose time will almost certainly come, sooner or later.

Much farther south, an adult cane toad was last week found squatting on the tarmac of Melbourne's Tullamarine airport after, it is supposed, hitching a ride on a passenger jet from Fiji.

The much cooler ponds around Tullamarine could allow cane toads to settle, but never comfortably and, said Professor Mike Tyler, Australia's leading expert on the subject, never as a dominant species.

Two decades ago, Tyler, of the University of Adelaide, was in Perth helping to find and kill cane toads which had similarly hopped off an aircraft and were still disturbingly active at a few degrees above freezing point.

"They're pretty resilient. They live in areas where you get -1C on at least three days a year."

This is scary stuff even for a nation accustomed to the ravages of imported plagues ranging from devastating water weeds and snails to rabbits, foxes and wild cats.

Since arriving in Australia in 1935 as a biological weapon against pests in sugar cane - and immediately establishing themselves as a far more devastating problem than the one they were imported to solve - cane toads have spread inexorably across the continent.

Moving at 40km to 50km a year, they have moved north from Queensland's canefields, west across the Northern Territory, crossing the Stuart Highway bisecting Australia a year ago, and moving more slowly south down the eastern seaboard as far as Port Macquarie, 423km north of Sydney.

Tyler says they will ultimately pass through Darwin and through the vast Kimberley region of northwest Australia to Derby and possible Broome, and down the East Coast as far as Batemans Bay, three hours drive south of Sydney.

Cane toads are toxic, and fatal to native predators - even species as large as crocodiles. The unexpected appearances of the toads in Menai and Melbourne were yet another frightening warning for a country which, Tyler complains, is spending almost nothing on controlling the toads.

"Chemical or physical control is out because they now occupy a huge geographical area."

Tyler said long-term biological control was the only feasible solutions, but with the exception of "a little bit of genetic tinkering" at the Commonwealth Scientific and Industrial Research Organisation, Australia's major science organisation, there was no Government funding for cane toad research.

"So much money is spent on foxes, rabbits, donkeys and other creatures which are regarded as pest species, which in Australia are defined as ones which have caused the extinction of two or more native species, and/or have an impact on primary production.

"The cane toad does not fit into either of these categories and therefore its not a pest."

Tyler said if funding was available researchers could investigate the potential of repellents or attractants, based on the toads' enormous sensory organs - much larger than their brains - which gave them a very acute sense of smell.

"The sort of thing we wonder is whether we can attract them into areas where they can be killed, using perhaps the toads' own chemistry, some of the secretions from its skin, or whether in fact we can find a repellent.

In the meantime, the toads have now established themselves in one of the worst-possible areas of Australia - the Northern Territory's World Heritage-listed Kakadu National Park.

Their presence has been confirmed at Jim Jim Falls, on the southeast tip of the vast park, and at Mary River, the waterway skirting the park's southwestern border.

Kakadu is a huge reservoir of biological diversity, home to as many as 60 species of native fish, 287 species of birds, 60 mammal species, 120 kinds of reptiles, and 25 varieties of frogs, 10,000 types of insects and more than 16,000 plant species.

"The cane toad will become the dominant form of life," Tyler said.

"If I hadn't seen Kakadu and I wanted to, I'd go up this year - because this may be the last time without cane toads."