‘Surprising’ study finds Qld crocs stay close to home

Keira Jenkins |

Crocodiles in Queensland are happy to stay close to home unlike their NT cousins, a study has found
Crocodiles in Queensland are happy to stay close to home unlike their NT cousins, a study has found

Queensland crocodiles like to stay close to home with most remaining within 50km of where they hatched, unlike their wide-roaming counterparts in the Northern Territory.

In fact, most crocodile parents and offspring in Queensland are found within 10km of each other, a joint Department of Environment, Science and Innovation (DESI)-CSIRO study found. 

The results have surprised researchers who had treated Queensland crocodiles like their Northern Territory counterparts, which are known to travel 200km or more.

While crocodiles are capable of moving anywhere along Queensland’s coastline, the study showed most of the 20,000 to 30,000-strong population were in the far north.

There was no evidence of expansion south of the Fitzroy River at Rockhampton in central Queensland.

DESI’s Simon Booth said the results redefined what was known about Queensland’s crocs. 

“It was a little bit surprising,” he told AAP.

“We’ve always treated our crocodile population in a similar vein to the Northern Territory’s and with more research we’re going to understand the uniqueness of the Queensland crocodile population.”

Researchers tested genetic samples from 1176 saltwater crocodiles, collected between 1997 and 2021.

They found there are six crocodile populations in Queensland, which live within 12 distinct regions across the state.

Almost 80 per cent of Queensland’s crocodile population is located north of Cooktown and in the Gulf of Carpentaria in the far north.

The remainder are found along the coast between Cooktown and Rockhampton, which is the southern-most population anywhere in the world, according to Mr Booth.

Only 10 per cent of Queensland crocodiles were found at a distance greater than 50km from their relatives.

In contrast, more than 40 per cent of the Northern Territory’s crocodile population travel 200km or more. 

Mr Booth said differences in habitat and population density account for the variation in crocodile movements. 

“Queensland, generally speaking, doesn’t have huge expanses of floodplains like in the Northern Territory, which can assist in movement and dispersal over greater distances,” he said.

“Our crocodiles have to make their way out of river systems and along the coastal areas if they’re wanting to move any reasonable distance.

“We have significant lower densities and lower numbers in terms of crocodile population … the crocodiles simply aren’t being driven out as much and having to move as far as they mature.”

Mr Booth said the results could have important implications for crocodile management.

He said strategies could differ between regions, depending on the size of the population and balancing the goals of public safety and crocodile conservation. 

“We need to be quite considered in how we undertake management of crocodiles and certainly problem crocodiles,” he said.