By Phil Mercer
BBC News, Sydney
Three homesick crocodiles in Australia have shocked experts by returning hundreds of kilometres back to their homes after being relocated.
Craig Franklin (R) paid tribute to colleague Steve Irwin (L)
The discovery was made after tracking devices were attached to the reptiles.
Saltwater crocodiles caught near popular Australian beaches and rivers are often shipped to more remote areas.
But the policy of relocating rogue crocodiles will now be questioned - since it seems the animals have a well-developed homing instinct.
Researchers said the results of their study were "staggering".
"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," added Professor Craig Franklin, from the University of Queensland.
One large croc was trapped on the west coast of Queensland's rugged Cape York Peninsula.
It was flown by helicopter to the east coast. Within three weeks it was back home, after a journey of more than 400km (250 miles).
The other crocodiles in the experiment did exactly the same. They were, according to one scientist, just like boomerangs.
It is unclear, though, what enables the reptiles to navigate so skilfully.
The homing capabilities of the crocs staggered the team
Professor Franklin said crocodiles probably used many factors such as their position to the Sun, magnetic fields, sight, and smell to navigate.
"Crocodiles are more closely related to birds than they are any other reptile so they are possibly using navigation systems similar to birds," he added.
The Queensland professor paid tribute to the late naturalist Steve Irwin who was a major driving force behind the study. Irwin, famous for his appearances on TV with crocodiles, was killed in September 2006 when a stingray barb pierced his heart as he was filming an underwater documentary.
The long-distance estuarine crocs (Crocodylus porosus) are featured in a paper in the (Public Library of Science) PLoS ONE journal.
The project was a collaboration between the University of Queensland, Australia Zoo and Queensland Parks and Wildlife Service.