Clever Crocodilians Trick Nest-building Birds with Sticks as Lures

Crocodiles and fishermen don't have much in common, but new research suggests that they both share the use of lures when looking to make a catch.

Two crocodillain species - muggers and American alligators - have been documented using twigs and sticks to lure birds. The reptiles display a remarkable cleverness by using these wooden lures to attract birds in the midst of building a nest.

The observations, which are reported in the journal Ethology, Ecology and Evolution, mark the first use of tools ever documented in a reptile species. It is also the first known case of a predator timing its use of lures with a seasonal behavior of its prey.

Vladimir Dinets, a research professor at the University of Tennessee, and his colleagues first made the observations in 2007 in India. He witnessed crocodiles there lying in shallow water along the edge of the pond with small sticks or twigs positioned in their mouths so that they jutted out beyond the reptiles' snouts. The crocodiles would lay in wait, motionless until a bird wading through the water to collect nest-building material came close enough to the trap. Then the crocodile would lunge at the bird, often successfully obtaining a meal.

Back in America, Dinets and his team went to Louisiana to see if the same clever luring behavior could be observed in other species. The team spent a year observing American alligators at four sites in Louisiana. Two of the sites were near known bird nesting grounds, while the other two were not.

The researchers observed the behavior in the American alligators, with a pronounced occurrence of the luring tactic between March and May, which is the nest-building season for birds in the area.

"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 signaling, advanced parental care and highly coordinated group hunting tactics."

Dinets also noted that the luring behavior observed in American alligators and the mugger crocodiles in India could be indicative that the behavior is more widespread within the crocodillian order, and perhaps even provides insights into the behavioral patterns of extinct reptiles such as dinosaurs.

"Our research provides a surprising insight into previously unrecognized complexity of extinct reptile behavior," Dinets said. "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."