August 28, 2008

Study Suggests Toads May Avoid Cooler Regions Of Australia

A recent study suggests that cane toads may avoid certain cooler and drier regions of Australia during their migration.

Scientists staged a 2m sprint event in their own laboratory "Toad Olympics".

Toads from the frontline of the invasion could only hop at 0.3 km per hour at 15C, but as fast as 2km per hour at 30C, Ecography journal reports.

They concluded that areas like Melbourne that are cooler and drier may not witness the massive invasion of the cane toad.

Originally introduced to north-eastern Australia in 1935 as pest control agents, these warty and poisonous amphibians are explosive breeders.

Now, they pose a threat to Australia's native wildlife.

Previous studies suggested that the toads would eventually invade Melbourne and other southern regions of Australia, but Dr Kearney from the department of zoology at the University of Melbourne said: "The toads have made it to Darwin where they are doing well. They have had trouble establishing in Sydney despite lots of toads finding their way there. But our predictions make us feel quite safe from toads in Melbourne."

"We considered the ability of adult toads to move around on the surface, and the potential for the toad tadpoles to develop successfully," explained Dr Kearney.

Scientists used computer models to determine the current climatic conditions across Australia as well as predict future climate change.

In the study, toads hopped at speeds of more than 50km per year in warmer areas.

But in southern Australia, "it simply becomes too cold for (them) to move around", explained Dr Kearney.

"The cane toads cannot survive in much of southern Australia because they would be too cold to move about and forage or spawn," he said.

"The toads are also likely to be limited by dehydration as they move inland."

The scientists suggest that their approach could be applied to study the effect of climate on other organisms.

"We are currently using it to study butterflies, disease-causing mosquitoes and possums," commented Dr Kearney.


Image Caption: Cane Toad. Courtesy Bill Waller (Wikipedia)


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