http://www.nytimes.com/2007/10/16/science/16obtoad.html?ref=science Arthritis Fails to Slow Invading Toads in Australian Fields
By HENRY FOUNTAIN
It couldn’t happen to a nicer bunch of toads.
Researchers have found that the cane toad, one of the most invasive species anywhere, is paying a price for conquering northern Australia. The toads are growing so big and hopping so rapidly into new territory that they are developing severe arthritis...Cane toads were introduced in Australia in the 1930s in an effort to control insects in sugar cane fields. But the toads, which are toxic to snakes and other animals that try to eat them, quickly expanded beyond their initial habitat. Cane toads can now be found across about 400,000 square miles.
An earlier study found that toads at the leading edge of the expansion — the invasion front, as it were — had evolved to move faster, with longer legs and larger bodies...The researchers, who report their findings in The Proceedings of the National Academy of Sciences, suggest that some of the same factors that have made the toads successful invaders have led to their health problems. The toads are big and growing bigger, and generally, large size increases susceptibility to arthritis...
The toads are so active that they are hopping more, and with their longer legs, each hop puts greater stress on their skeletons.
In laboratory tests, the researchers found that after about 15 minutes of hopping, arthritic toads would cover less distance with each hop. But arthritis didn’t slow down toads in the field, the researchers found. These toads are so programmed to move, apparently, that the hobbled toads traveled as fast and as far as healthy ones, continuing their relentless march across the landscape.
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