Queensland’s saltwater crocodiles live in six distinct populations

The genetics of Queensland’s crocodiles have been studied and scientists are surprised by the results.

Crocodiles in Queensland travel less than previously believed and live in just six broad population groups, according to new research that has redefined what was known about the reptiles.

The genetic study, by the state environment department and the CSIRO, also found that approximately 91 per cent of Queensland’s saltwater crocodiles live within 50km of where they hatched.

It has overturned the previously established concept that saltwater or estuarine crocodiles would move everywhere and anywhere to breed, and it could lead to more localised conservation and management programs.

Almost 1200 samples taken from crocodiles between 1997 and 2021 were used to map out the diversity of the population living along the Queensland coastline and monitor their movements.

The Department of Environment and Science’s program co-ordinator for wildlife monitoring and research, Simon Booth, said the results of the research would help inform government policy relating to managing human and crocodile interactions.

“Although estuarine crocodiles are capable of moving anywhere along Queensland’s coastline, the study has redefined what we know about Queensland’s crocodile population,” Mr Booth said.

“Importantly, the genetics study has shown where crocodiles come from, where they go, and how far they travel.

“This information can help us to manage local populations, and we will use the findings to help inform the management of crocodiles.

“The Queensland government will continue to help keep people safe while ensuring the ongoing survival of crocodile populations in the wild.”

The six genetic groups identified in the study were located in the regions surrounding the Fitzroy River, Proserpine River, northern east coast, northeast Cape York and Rinyirru, northwest Cape York and Torres Strait, and the Gulf of Carpentaria.

Researchers found there was little interaction between the subgroups, particularly in the more southern populations.

Previous population studies have estimated there are between 20,000 and 30,000 saltwater crocodiles in Queensland.