Rangelands NRM Blog, News & Resources

Hope for adapting Kimberley crocodiles as cane toad approaches

[Sept-Oct 2016]

Crocodile numbers are likely to fall following the invasion of cane toads in the Kimberley, but at the same time the population will adapt and grow stronger and resilient, according to a CSIRO biologist.

Over one hundred people attended the talk by CSIRO freshwater crocodile biologist Dr Ruchira Somaweera on 20 September, as part of the popular Science on the Broome Coast series. He was also joined by Parks and Wildlife estuarine crocodile scientist Dr Andrew Halford who spoke on saltwater crocodiles.

Roebuck Bay Working Group Project Manager Kandy Curran said Dr Somaweera predicts a likely severe decline in freshwater crocodile numbers in some parts of the Kimberley with the invasion of cane toads.

Dr Somaweera said that although cane toads are the biggest threat to ‘freshies’, other threats include invasive weeds such as exotic passionfruit vine that can choke river bank nesting habitats, bycatch in fishing, and predation by their saltwater relatives.

Two studies in the Northern Territory along the Daly and Victoria River systems showed significant population declines (77 per cent and 60 per cent respectively), highlighting the concern for the Kimberley freshie.

There is hope, however, for Crocodylus johnstoni.

Dr Somaweera said recent studies show freshwater crocodile hatchlings are intelligent and can develop a taste aversion for toxic toads if they experience a non-fatal experience from eating a juvenile that has made them ill.

“I think we will see a phase of severe decline, and then those that have adapted will form a stronger population,” he said.

The talks are hosted by the Roebuck Bay Working Group and Yawuru Land and Sea Unit in Broome, and sponsored by Inspiring Australia, Rangelands NRM through the Federal Government Landcare Programme, State NRM through Royalties for Regions, Western Australian Marine Science Institution, Department of Parks and Wildlife and University of Notre Dame Broome.

(Article adapted from original published by WAMSI, by Kandy Curran)

(header) Dead ‘freshie’ and cane toad © Ruchira Somaweera
Dr Ruchira Somaweera presenting in Broome at the Science on Broome Coast series © Kandy Curran