Animals

Aussie Crocs Found to Swim Up to 24 Miles Daily

By Andrea Thompson, LiveScience Staff Writer

posted: 25 September 2007 10:45 pm ET

: Estuarine crocodiles, the largest of all living reptiles, were found to swim much larger distances than expected, finding their home from hundreds of miles away. Credit: C. Franklin

Known for their lethargy, crocodiles weren't suspected to be top long-distance travelers, but a new study shows that they can cover up to 24 miles a day and find their way home from enormous distances.

To test crocodile swimming skills, researchers relocated three crocs between 32 and 80 miles (52 and 130 kilometers) away from their homes just north of Queensland, a state in the northeast of Australia, and set them free to see how well they could find their way back.

The study technique was largely put into practice by the efforts of the late Steve Irwin. Specially-designed transmitters attached to the back of the reptiles' heads allowed scientists to monitor progress, with some astounding results: the crocs swam between 6 and 24 (10 and 39 kilometers) a day, much farther than scientists previously thought they could.

One crocodile even swam around the northern tip of the Cape York Peninsula (which juts northward out from Queensland toward Papua New Guinea) to reach home, covering more than about 250 miles (400 kilometers) in 20 days.

"We often thought crocodiles tired very quickly, but here we show very clearly that they are capable of moving long distances for days on end," said study leader Craig Franklin of the University of Queensland.

Franklin says that the crocs, like birds, probably use many factors to navigate, including the position of the sun, magnetic fields, sight and smell.

"Crocodiles are more closely related to birds than they are any other reptile, so they are possibly using navigation systems similar to birds," Franklin said.

The data from the satellite tracking study, detailed in the online journal PLoS ONE, show that estuarine crocodiles are capable of moving phenomenal distances over prolonged periods of time in the ocean.