Invasion Is Backbreaking Work For Australia's Cane Toads

While conducting research into toad invasion front, scientists from the University of Sydney and from the Department of Primary Industries found that the larger 'invasion front' toads were displaying a high incidence of spinal abnormalities.

'Bigger, longer legs increase their ability to seek out new territory but also puts pressure on the body with every hop,' said Professor Shine from the University's School of Biological Sciences. '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.'

'We found that around 10 per cent of toads had arthritis in their spine,' said Professor Shine. 'Ironically, factors that have contributed to the toads' rapid spread across the continent have also rendered it susceptible to arthritis,' he said.

The researchers also observed that the process of invasion appears to have selected for larger toad body sizes on the invasion front.

'Whilst the larger body size provides advantages to the coloniser, as they can move faster, eat a wider range of prey and are less vulnerable to predators, it also increase their susceptibility to arthritis,' he said.

'The major spinal deformations of these animals testify to the great stress that invading species place upon themselves, as well as upon the ecosystem they are overrunning. An important aspect of this research is that it highlights the importance of incorporating wildlife health perspectives in any analysis of the process of biological invasion,' said Professor Shine.

Their findings are published online in the Proceeding of the National Academy of Sciences, in a paper entitled 'Invades under stress: spinal arthritis ion invasive cane toads'.