It sounds counter-intuitive, but an Australian expert on the noxious cane toad suggests setting them loose to give native animals chance to learn to defend themselves.

Setting cane toads loose in areas of Australia that don’t already have them may sound like a crazy idea, but research by Professor Rick Shine, from the University of Sydney, suggests that this could lessen the impact of the toad.

The cane toad, Bufo marinus, is a huge pest in eastern Queensland and is rapidly spreading westwards across the Northern Territory into Western Australia, and south through New South Wales.

Cane toads were introduced into the sugar cane growing state of Queensland in 1935, to combat the cane beetle, a pest of sugar cane crops.

However, as the toad is not native to Australia, it has no predators, and has since spread across most of Queensland and almost entirely across the Northern Territory, including the world-renowned wetlands of Kakadu.

Cane toads are highly poisonous at all stages of life, and as well as taking over the habitats of native reptiles, they generally poison any bird or mammal that eats them.

Toads Kill Native Australian Animals

One of the cane toad’s biggest impacts is killing native Australian animals that eat the poisonous amphibian. Populations of the Northern Quoll, a threatened species, have been decimated by eating cane toads, as have native goannas, snakes, and even freshwater crocodiles.

“We’ve had no effective way to stop the impact of cane toads on our native fauna,” said Professor Shine.

“The problem is that all of the toads at the invasion front are very large animals – so large that when a predator attacks one, it is exposed to a lethal dose of poison.”

‘Teacher Toads’ to Train Predators

Professor Shine’s idea is to seed areas with ‘teacher toads’ – small cane toads that are not yet capable of killing their predators, but can give them a nasty shock.

“Small toads could be dropped into areas in advance of the spreading cane toad front, to act as ‘teacher toads’ for native animals. Native animals survive their first encounter with the cane toads, but get slightly ill and learn to keep away,” he said.

“If the first cane toad that a predator encounters is a small one, it can survive the experience and learn to stay away from other toads.

“So we can teach native animals to stay away from cane toads, by giving them a scare with a smaller, less poisonous cane toad, and reduce the number of native animals dying.”

To stop these ‘teacher toads’ becoming a menace in their own right, Shine uses sterile male toads which are unable to reproduce.

Research by Professor Michael Mahony at Newcastle University in NSW has made producing sterile male cane toads in large numbers straightforward.

Professor Shine’s research group, Team Bufo, have collected detailed data on the effectiveness of ‘teacher toads’ on native fish, frogs and marsupial predators, but he said more work needs to be done with reptiles.

Native frogs, fish and mammals learn very quickly when they encounter the ‘teacher toads’.

Parasitic Lung Worms to Control Toads

Team Bufo have also been studying parasitic lung worms, which are capable of killing cane toads in large numbers.

This is not, as was first thought, an Australian lung worm that had shifted from native frogs to the toads, but is a South American parasite that arrived with the cane toads.

“This is great news for reducing the number of cane toads – we can use the South American lung worm as a biological control and be sure that it will not infect native frogs,“ Professor Shine said.

“Using both methods together will decrease the number and impact of cane toads in Australia.”

Professor Shine has set up a special website to explain his new ideas in toad control.

See also: Back Pain in Poisonous Cane Toads