Saltwater crocodiles are making marathon ocean swims to reach home even if they are airlifted hundreds of kilometres away, new research shows.
Three relocated crocodiles in Far North Queensland have been tracked swimming between 10 and 30 kilometres per day with one crocodile swimming around the northern tip of Australia to reach home —covering more than 400 kilometres in 20 days.
The results are from the first satellite tracking study of wild crocodiles undertaken by UQ, Australia Zoo and the late Crocodile Hunter Steve Irwin and Queensland Parks and Wildlife Service (QPWS).
Using tracking data from 2004, the team found crocodiles had remarkable homing and navigational skills and stamina to swim large open water voyages.
All three monitored crocodiles were moved by helicopter between 52 and 130 kilometres away but still found their way back to their capture sites.
One crocodile was flown across Cape York Peninsula from the west to east coast and then circumnavigated the peninsula to return home.
Project researcher Professor Craig Franklin, from UQ’s School of Integrative Biology, said the data showed that crocodiles were oceanic animals which could move phenomenal distance over a prolonged period of time.
“We often thought crocodiles tired very quickly but here we show very clearly that they are capable of moving marathon distances for days on end,” Professor Franklin said.
Crocodiles were tracked using a specially-designed transmitter attached to the back of their heads that collected data and relayed it via satellite back to the scientists.
Professor Franklin said the study showed that moving problem crocodiles away to remote river systems was not effective.
"Moving crocodiles to isolated waterholes which are surrounded by land might prove to be an effective impediment to them returning home."
He said the results also proved the success of satellite tracking for crocodiles allowing continuous tracking without human interference.
"Satellite technology is a great way of tracking these really cryptic animals which are difficult to follow.
"Steve Irwin was a major driving force behind the study, and his intellectual and logistical support complimented the knowledge, experience and contributions made by the other team members.
"He also gave us the assistance of the croc team from Australia Zoo who are highly skilled in the capture and care of crocodiles."
Professor Franklin said crocodiles probably used many factors such as its position to the sun, magnetic fields, sight and smell to navigate.
“Crocodiles are more closely related to birds than they are any other reptile. Maybe they are using navigation systems that are similar to what occurs in birds?”
The collaboration was led by Dr Mark Read from the QPWS and funded by an Australian Research Council grant and bequest from the late Cooktown herpetologist Charles Tanner.
The team’s results will be published in the open access online journal, Public Library of Sciences One (PLoS ONE).
Professor Franklin said further satellite and acoustic tracking studies would reveal even more impressive results about crocodile behaviour, particularly about their navigation.
MEDIA:
- Professor Craig Franklin (+61 7 3365 2355, +61 (0)434 602 327, c.franklin@uq.edu.au)
- Dr Mark Read ( +61 7 4046 6654, mark.read@epa.qld.gov.au)
- Miguel Holland at UQ Communications (+61 7 3365 2619)
(*Hi res photos available from Diana Lilley on 3365 2753, d.lilley@uq.edu.au)
