for National Geographic News
The toads that jump—and thus populate new territory—the fastest are more likely to be larger and have longer legs. But this advantage also has a drawback: up to 10 percent of the biggest invasive toads suffer from arthritis, a new study says.
The large, yellow toads, native to South and Central America, were introduced into the northeastern state of Queensland in northern Australia in 1935 in an attempt to stop cane beetles from devastating sugarcane crops.
Now up to 200 million of the poisonous toads exist in the country, and they are rapidly spreading west through the state of Northern Territory at a rate of up to 37 miles (60 kilometers) a year. (Related news: "Poison Toads Leap Across Australia" [November 29, 2004].)
The toads haves severely impacted ecosystems in Australia. Predators—and sometimes pets—that eat toads die immediately from their poison, and the toads themselves feast on any animal they can fit in their mouths. Cane toads also compete with native frogs for habitat.
Evolution of the Fastest
Study co-author Rick Shine is a professor in evolutionary biology at the University of Sydney.
"There has been lots of attention [given] to the impacts of invading species on natural ecosystems, but less thought has been given to the challenges that the invaders face themselves," he said.
Shine and colleagues studied nearly 500 preserved toads from three populations: one from Queensland and two from the Northern Territory. (See a map of Australia.)
The Northern Territory toads that Shine's team studied were very different from their Queensland relatives.
"They are very active, sprinting down the highway and breeding as they go. They are moving as fast and as far as you can imagine," Shine said.
The fastest toads travel nearly half-a-mile (one kilometer) a night, he added.
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