Fewer freshies but salty crocs on the rise

Pilbara News - - News - Robert Dougherty

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.

Pic­ture: Depart­ment of Parks and Wildlife

A salt­wa­ter crocodile on the muddy banks of Dampier Creek in Broome.

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