How to teach a goanna that eating a cane toad is a bad idea

Georgia Ward-Fear with a captured floodplain goanna. Balanggarra Rangers Herbert and Wesley Alberts in the background. Image: University of Sydney

Australian scientists have taught wild goannas to avoid eating poisonous cane toads.

“After training, giant monitor lizards, known as goannas, survived when the toads arrived, whereas untrained lizards were immediately killed,” says University of Sydney PhD candidate Georgia Ward-Fear, who led the research under supervision from Eureka Award-winner Professor Rick Shine with colleague Dr Gregory Brown.

The yellow-spotted monitor, or floodplain goanna, weights in at 7kg, is central to Aboriginal culture and plays a pivotal ecological role.

The spread of cane toads, introduced into Australia in 1935 from South America to control destructive beetles in Queensland’s sugarcane crops, across northern Australia has caused catastrophic population declines in many native predators.

Smaller predators often survive because the toads they attack are small enough to make them sick but not kill them. Small toads contain much less poison than adults.

Immediately before the arrival of toads at a remote floodplain at Oombulgurri in the Kimberley region of northwestern Australia, researchers offered small (non-lethal) cane toads to wild lizards. Follow-up trials confirmed just one or two toad meals were enough to convince a goanna not to eat another toad.

The trained lizards then went on to ignore the large toads which arrived a few months later. Eighteen months after the study started, many of the trained lizards are still alive despite the presence of toads.

The research led by University of Sydney is published in the journal Biology Letters. The work was carried out in collaboration with the Western Australian Department of Parks and Wildlife and Balanggarra Rangers.

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