Clever crocodiles and alligators use traps to lure prey into their deadly jaws, scientists have discovered.
Researchers at the University of Tennessee said that the reptiles' intelligence had been underestimated and that they were smarter than previously thought.
Vladimir Dinets, of the university's Department of Psychology, observed some species of crocodilia using twigs and sticks to lure birds, particularly during nest-building times.
Mugger crocodiles and American alligators were first observed luring their pretty with sticks in 2007 by Dinets when watched them lying in shallow water along the edge of a pond in India.
He noticed small sticks and twigs positioned across their snouts - attempting to fool unsuspecting birds into venturing on to their jaws to collect them.
Published in the journal Ethology, Ecology and Evolution, his study is the first report to show tool use by any reptile and the first known case of predators timing the lure to a specific season.
Researchers observed the reptiles for a year at four sites. They noticed a significant increase in alligators putting sticks on their snouts between March and May. The authors believe this behaviour is probably more widespread within the reptilian group than currently thought and may shed light on how dinosaurs (the extinct relatives of crocodiles) behaved.
"This study changes the way crocodiles have historically been viewed," Dinets said. "They are typically seen as lethargic, stupid and boring but now they are known to exhibit flexible multimodal signalling, advanced parental care and highly coordinated group hunting tactics.
"Our research provides a surprising insight into previously unrecognised complexity of extinct reptile behaviour.
"These discoveries are interesting not just because they show how easy it is to underestimate the intelligence of even relatively familiar animals, but also because crocodilians are a sister taxon of dinosaurs and flying reptiles."