They don’t just lie about on river-banks, pretending to be lifeless logs waiting to bite your legs off. Primeval reptiles though they may be, crocodiles are clever.

Australian scientists have discovered that the long-established practice of capturing and removing the most aggressive crocodiles from Outback swimming holes used by tourists, and dumping them in remote locations, could be a waste of time. They can find their way back.

In fact they are capable of complex navigation over long distances.

Scientists using satellite tracking devices fitted to wild crocodiles found that they have the sophisticated navigational intelligence and stamina of long-distance migratory birds.

Three of the beasts were taken from their home rivers in far northern Queensland by helicopter and carried hundreds of miles before being released in distant locations. All three made it back to their home rivers, swimming between 6 and 19 miles a day. One swam round the northern tip of Australia to reach its home after a journey of more than 250 miles in 20 days.

The findings - released this week by a University of Queensland team in the online scientific journal PloS ONE - followed the world’s first satellite tracking study of wild crocodiles undertaken by the University of Queensland and Australia Zoo, which was founded by Steve Irwin, the naturalist who was killed by a stingray last year.

Craig Franklin, of the University of Queensland’s School of Integrative Biology, said the results showed that crocodiles were oceanic animals that could move phenomenal distance over a prolonged period. “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.

Each of the crocodiles spent weeks exploring its new location before setting out on its homeward journey. The study observed: “It is noteworthy that all three individuals spent some time at the release point before embarking on an apparently purposeful and direct travel homewards.

“Our observations clearly imply that crocodilians are skilful at interpreting a suite of complex cues for orientation and navigation, and this aspect of their behaviour demands additional investigation.”

The crocodiles were tracked using special transmitters attached by wire cables to the backs of their heads. These collected data and relayed it via satellite to the scientists.

The study showed that moving dangerous and potentially man-eating crocodiles away to remote river systems is not effective. It concluded: “If a problem crocodile animal is living in an area where conflict with humans is likely, then other options need to be employed. Of particular interest were the large distances travelled in a comparatively short time.”

Professor Franklin said that Irwin, who was famous for his work with crocodiles, had been an important driving force behind the study.

He added that crocodiles probably used many factors, such as 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.”

Professor Franklin said that further satellite and acoustic tracking studies would reveal even more impressive results about crocodile behaviour, particularly their navigation.

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