DNA database reveals origins of crocs caught in Darwin Harbour

An analysis of crocodile DNA has revealed where the majority of beasts caught close to Darwin have travelled from. Read what the study found.

Academics Yusuke Fukuda and Professor Sam Banks explored where saltwater crocodiles caught in Darwin Harbour had migrated from in a new research paper. Picture: Supplied

A crocodile DNA database has helped reveal the origins of problem crocs caught in Darwin Harbour.

A study on the migration patterns of saltwater crocodiles showed that some of the reptiles had come from as far as 700km away.

Lead author of the study, NT government Department of Environment, Parks and Water Security wildlife scientist Yusuke Fukuda said most of the beasts causing problems near Darwin had travelled between 100km and 200km.

What the lure is for them to be closer to the city is not fully known, but it is potentially in search of new territory and resources.

A crocodile trap floats in front of mangroves in Darwin Harbour. Picture: Che Chorley

The majority of crocs had made the trek from Adelaide River, Mary River and Kakadu, while about 30 per cent of those studied had come from the Daly, Finniss and Reynolds river region.

Fifteen per cent of crocs come from Tiwi Islands.

Mr Fukuda said the results of the study could inform management practices in the NT.

“One of the reasons we did the study was that it might tell us whether there are other ways of managing the problems caused by crocodiles migrating to Darwin Harbour,” he said.

“For instance, if crocodiles were only coming to Darwin from a small number of catchments close to Darwin, we could target management (e.g. egg collection) to those places to reduce the number of young crocodiles moving along the coast to look for a home.

“However, the results reinforce the need for management in Darwin Harbour rather than targeting source populations of problem crocodiles, as they can reach Darwin from a long way away. ”

Crocodiles caught from within the Darwin Harbour management zone. Picture: Annabel Bowles

Each year more than 250 crocodiles are captured from Darwin Harbour.

So far 102 reptiles have been taken from the upper and lower harbour management zones.

Charles Darwin University Research Institute for the Environment and Livelihoods director Professor Sam Banks said the research was ‘exciting’.

“This gives us a crocodile equivalent of the ancestry testing that people can pay for to find out the history of their own DNA, except that it allows us to work out with quite high accuracy where a crocodile was born right across Australia and Southeast Asia,” he said.

“It’s really exciting to have crocodiles at the forefront of DNA technology for wildlife management — This is a resource that we can use into the future to help with better monitoring and management of crocodiles in the NT, across Northern Australia and overseas.”