May 29, 2014
With another discovery of cane toads in Perth this week, it seems efforts to stop the spread of the animal are not working.
“There is nothing we can do to stop them,” says Associate Professor Peter Spencer, head of Wildlife DNA Laboratory at Murdoch University.
“They are here and they are out of control.”
First introduced to Australia in 1935 to control the native cane beetle which was damaging sugar cane crops in Queensland, the cane toad has been in WA’s far north for three years and is gradually spreading south.
To date, 36 cane toads have been recorded to have reached Perth from the Kimberley or from the eastern states, according to Heather Quinlan from the Department of Parks and Wildlife.
Most recently, seven live and two dead cane toads were found in a shipment of mango plants from Kununurra.
The toads were discovered by accident during the unloading of a Toll Express truck at the Perth Airport depot.
No official checking system is in place even though officials acknowledge “hitchhiking” is the most likely way toads get to Perth.
“The entire community, including the trucking industry and primary producers, play a major role in helping to address this risk by being vigilant and checking their loads before departing these areas,” Ms Quinlan says.
Fortunately, it is unlikely the cane toad could establish a big population in metropolitan Perth as the climate is not suitable.
The case of cane toad spread throughout northern Western Australia is more concerning.
Winthrop Professor Dale Roberts from the University of Western Australia has led research in the area and been involved in numerous cane toad evaluation workshops.
“They clearly can spread right across the Kimberly, and they are going to get all the way to Broome,” he says.
“There’s been no argument about that. If you look at the modelling of cane toad distribution, they are likely to get into the continuously wet season in the Pilbara.”
Associate Professor Spencer agrees.
“They sit in rafts of debris and get washed out in the wet season,” he says.
“Enormous amounts of water runs through these river systems. You can’t just sit there spotting them form the top of a cliff and then go down and pick them all. They are a wild animal.”
Initiatives such as the Cane Toad Hotline, drop off points for toad disposal and even a phone App which helps to correctly identify the invasive species have had some impact on preventing human-aided spread, but experts say we simply cannot stop the natural movement of the animal.
Some hope exists for the south-west. Professor Roberts says models of the physiology of cane toads and what temperatures they can tolerate suggest they probably would not do well in south Western Australia.
“If you look at the eastern States, they haven’t moved down the east coast when they have had plenty of time do that,” he says. “They are reaching the physiological limits of their survival.”