Cane toads have adapted to our climate
Cane toads (Rhinella marina), introduced to Australia to eliminate the native grey-backed cane beetle but has since become a threat to the Australian ecosystem, is adapting to our extreme climate.
The research, conducted by the University of Sydney and Charles Darwin University, shows that scientists looking to control cane toad populations in certain areas, can not rely upon past observations to predict where the pest will next disperse.
In 2011 Professor Rick Shine from the University of Sydney predicted this sequence of events by suggesting that the toads will be relatively common and widespread.
Here to stay
It’s now official: our cane toads are unstoppable. The poisonous pests have established themselves in Kununurra, WA, and one recently hitchhiked all the way to Broome, on the north-west coast. In the east, a breeding colony has been discovered in a Sydney suburb.
So, not only have the toads hopped 2500km across the top of Australia, from coastal Queensland – where their forebears were released as a biological weapon against a sugar cane pest in 1935 – but they’re also heading south.
Native to south and central American rainforests, these giant amphibians have adapted so well to our conditions that they’re happy even in our arid interior. Toads are breeding in Longreach and Windorah, in central-west Queensland, and they’re infiltrating the NT’s desert regions via the Victoria River.
It means the cane toads have won. Having spent more than $20 million on attempts to control the invaders over the decades, the Federal Government has admitted defeat. Toads are here in their hundreds of millions. And they’re here to stay.
As the Government states in its 2010 draft Cane Toad Threat Abatement Plan: “Eradication of cane toads is not currently possible. Neither the resources nor the technologies required to contain and eradicate cane toad numbers on a continental scale are available.” All that’s left for the Government to do now is minimise the toxic toad’s impact on those native species that prey on it.
None of this is surprising to Sydney University reptile expert Professor Rick Shine, who became Australia’s cane toad guru after they overran his Kakadu snake study site in 2001. Not only are they at home in far harsher environments than those they left behind, but they’ve also evolved.
Spreading across the country
Initially able to move at only 10km a year, now they power along at 40–60km. And as well as getting faster, they’re bigger, have longer legs and now move in straight lines.
“In the race across the tropics, the fastest toads end up in front. Then they breed with each other and pass on those characteristics that help them move faster,” Rick says. Toads accelerate their progress by hitching lifts on trucks and have penetrated most of the country, including Melbourne and Adelaide.
The toad has bred in Sydney’s Taren Point for years, says Arthur White, president of the local Frog and Tadpole Study Group. “The worry is that they’ve dispersed and gone into other areas where we’ve got far less chance of catching them,” he says.
So what’s the future of cane toads? Rick says it’s probably in equilibrium. “Toads will be relatively common and widespread but not in current numbers. They’re adapting, but the native system is adapting to them as well.
Many predators that declined so dramatically when toads arrived more than 50 years ago are now relatively common again. Mother Nature is very resilient.”
