Cane toads pay dearly for stretching their legs

Arthritis affects amphibian advance

By Lester Haines • Get more from this author

Posted in Biology, 16th October 2007 13:57 GMT

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Scientists from the University of Sydney and the Department of Primary Industries have offered Aussies some slim hope that they will not ultimately be driven from the Lucky Country by rampaging hordes of cane toads who continue their inexorable march across Oz.

Cane toads were introduced into Australia from Hawaii in the 1930s in an attempt to combat the cane beetle. This turned out to be a very bad idea indeed, since they proved effective in combatting anything foolish enough to get in their path, advancing 3,000km across the country from their Northern Queensland start line at up to 40km a year, in the process swelling their ranks to an estimated 200 million individuals.

Indeed, in February 2006, we reported that a vanguard had penetrated to within 37 miles of Darwin, assisted by the simple trick of growing longer legs to speed their conquest.

University of Sydney researcher Richard Shine told Nature at the time: "We find that toads with longer legs can not only move faster and are the first to arrive in new areas, but also that those at the front have longer legs than toads in older populations."

However, they may now be about to pay the price for their cunning extended leg ruse. Richard Shine is now reporting that "larger cane toads invading NSW cities are suffering back pain and arthritis from their long trek".

Shine elaborates in the Proceedings of the National Academy of Sciences: "Bigger, longer legs increase their ability to seek out new territory but also puts pressure on the body with every hop. And, with much of their energy going towards movement, less is put into their immune system, which may predispose the toads towards infection with the soil bacteria that precipitate arthritis.

"Ironically, factors that have contributed to the toads' rapid spread across the continent have also rendered it susceptible to arthritis."

But before our Antipodean cousins fire up the celebratory barbie and crack a cold one, they should be aware that "only as much as 10 per cent of the larger-sized toads are beginning to show a high incidence of spinal abnormalities", leaving the vast majority fit and able to stretch their legs in pursuit of the final conquest of Down Under. ®

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