Australia mulls fences to halt cane toad invasion

Mar 7, 2011, 9:32 GMT

Sydney/London - Fencing off artificial water points such as irrigation ditches and troughs can help stop the advance of giant toxic toads in Australia, according to a University of Melbourne study headed by marine biologist Tim Dempster.

Writing in Proceedings B, the biological research journal of Britain's Royal Society, Dempster said the study had found that barriers 60 centimetres high placed around water points were enough to cause the cane toads to die of dehydration.

Cane toads (Bufo marinus), which are up to 25 centimetres long and two kilograms in weight, were introduced to Australia from Central America in the 1930s to control sugar cane beetles. But the toads have become pests themselves, spreading rapidly in north-eastern Australia and killing native animals that eat its poisonous flesh.

The artificial water points, particularly for livestock, have facilitated the spread of cane toads. Recent flooding in Australia has also helped them to advance into normally arid areas.

Dempster noted that artificial water points attracted cane toads from a wide radius, writing that they had been sighted at water points as far as 9.5 kilometres away from the nearest source of permanent water. In the study, Dempster and his fellow researchers fenced off water points and then collected and counted the toads outside them each morning.

By systematically excluding the toads from artificial water points, Dempster wrote, Australia could reduce the area of arid Australia across which they are predicted to disperse and colonize under average climatic conditions by more than a third, from about 2.2 million to 1.4 million square kilometres -- still about four times the area of Germany, however.

While fencing is no silver bullet in the war against cane toads, the researchers said, it could effectively reduce their numbers and keep them from spreading over large stretches of arid territory.

The mayor of the northern Australian city of Darwin, Graeme Sawyer, promotes fencing as a way to capture cane frogs in large numbers and has practical experience, too. His organization, Frogwatch, has fenced off some water points and then easily collected thirsty cane frogs that gathered there in the evenings.

'In four or five days you can practically remove the entire population from an area,' Sawyer told the German Press Agency dpa.

In Bridge Creek Station, about 120 kilometres south of Darwin, some 23,000 toads were removed this way about a year ago from a 110-square-kilometre area.