Close encounters in lab teach crocs to avoid toads

Baby freshwater crocodiles are rapidly learning not to attack toxic cane toads, according to new research from the University of Sydney.

Based at the university’s research facility at Humpty Doo in the Northern Territory, PhD student Ruchira Somaweera staged encounters between small toads and hatchlings from toad-free parts of Lake Argyle.

In the laboratory he found every hatchling attacked and consumed one of the toxic pests in the first instance, making the animal sick without killing it.

The reptiles quickly learnt to avoid toads as prey, and only four out of the 10 test crocodiles attacked a toad when the experiment was repeated.

Mr Somaweera said crocodile populations at Lake Argyle, unlike those in other parts of Australia, had not yet decreased.

He said the learning ability of the Lake Argyle hatchlings could be one reason why they were faring better than their NT counterparts.

“The impact of cane toads on crocodiles has been very heterogeneous,” Mr Somaweera said.

“In certain places like Victoria River there have been big crashes when the toads came, but then again there are other places like Lake Argyle or the Daly River where crocodiles haven’t shown (the same population decrease).

“Obviously at Lake Argyle you get dead crocs but the number of deaths you get is not enough at all to have a population level impact,” he said.