Fewer freshies but salty crocs on the rise
Scientists are predicting a severe decline in freshwater crocodiles in the Pilbara and Kimberley with the invasion of cane toads, while more of their saltwater cousins are expected to frequent coastal areas.
CSIRO freshwater crocodile biologist Dr Ruchira Somaweera and Parks and Wildlife estuarine crocodile scientist Dr Andrew Halford made the revelations to the Roebuck Bay Working Group during the Science on the Broome Coast forum at the University of Notre Dame Broome campus last week.
Dr Somaweera said the predicted slump in freshwater crocodiles was due to the advance of the reptiles’ biggest threat — cane toads — as well as other factors including bycatch fishing, invasive weeds and intrusion by their bigger saltwater relatives.
This could see WA follow a similar pattern to the Northern Territory, which has seen a 77 per cent decline of the reptiles at Victoria River and 60 per cent in the Daly River, according to two studies.
But Dr Somaweera said there was hope for the species with laboratory evidence that WA freshwater hatchlings could survive after attacking cane toads and learn to avoid them, which could then see a resurgence.
“I think we will see a phase of severe decline, and then the resistant animals will form a population,” he said.
Dr Halford said surveys conducted in the Roe River and Prince Regent areas had shown significant saltwater croc growth.
“Numbers are up in a range of a 100 to 300 per cent increase; it’s been 30 years so it’s a very clear example of what happens when you take humans out of the equation,” he said.
A saltwater crocodile on the muddy banks of Dampier Creek in Broome.