February 23, 2011

Scientists Find Cane Toads’ Achilles Heel

Scientists hope the toxic cane toad that has rampaged around northeastern Australia may at last be stopped.

The cane toad, which is a native of Central America, was introduced to Australia in 1935 to kill beetles devastating sugar-cane crops, only to become a pest in its own right.

However, a new investigation says the toad has an Achilles' heel.

The imported anuran desperately needs access to nearby standing water in order to survive, unlike indigenous amphibians that have adapted to arid conditions.

The study said that placing small fencing around man-made sources like irrigation ditches and troughs is enough to cause the toad to die of dehydration and stop its advance.

"Basically, step by step, toads use these water points to invade the drier regions of Australia," said University of Melbourne researcher Tim Dempster in an email to AFP.

"By stopping toads from using these water points, we are removing their 'stepping stones' in the landscape."

The cane toad can grow up to 10 inches long and weigh up to 4.4 pounds.

Dempster's team experimented with cane toads by placing some near nine artificial water points during the dry season in the Victoria River District of the Northern Territory.

Some of the water points were unfenced but others were surrounded by cloth netting 24-inches high that also extended along the ground to stop the toads from burrowing underneath.  The netting was secured by wire and metal posts at least 6.5 feet from the water's edge.

All 21 toads placed near fenced-off water points died, and most of them expired within 12 hours.

Of the 20 toads with unfettered access to water, all survived except for one, which was killed by a predatory bird.

Dempster said that fencing off even a small number of key water points can halt further invasion and save a 386,000 square-foot area out of the 865,000 square-foot area of arid land threatened by the beasts.

"The greatest benefit from the technique will be to stop further invasion into several of Australia's drier inland areas which are hotspots of unique native animal biodiversity," Dempster told AFP.

He said the method is feasible for water points that are around 70-feet across, but only key points would need to be fenced for the barrier to be effective.

Some experts say that cane toads already extend across 463,000 square-miles of Queensland and the Northern Territory and are on course for eventually spreading around three-quarters of Australia's coastline.

It has driven some native frogs and reptiles to near-extinction, inflicted catastrophic declines in snakes and crocodiles that snack on its flesh, and decimated goannas, which is a native lizard that is also a staple food in aboriginal communities.

The invasion has driven Australians to desperation.

Residents in toad-infested regions have resorted to gassing the reptiles, running them over in cars and even hitting them with golf clubs.  State authorities are encouraging the "toad busting" as well.

The study appears in Proceedings B, a journal of Britain's Royal Society.


Image Caption: Cane Toad Bufo marinus, Springbrook National Park, QLD Australia. Credit: Wikipedia (CC BY-SA 3.0)  


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