Crocodile's stick lure

This clever mugger crocodile (Crocodylus palustris) has placed sticks across its already well-camouflaged snout in an attempt, scientists say, to lure in birds as prey. (Vladimir Dinets / December 6, 2013)

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As if crocodiles and alligators weren't terrifying enough, scientists have discovered that these ancient, sharp-toothed beasts are incredibly cunning. So clever that they use lures to trap and gobble unsuspecting birds.

The discovery in two crocodilian species — mugger crocodiles and American alligators — is the first report of tool use in reptiles, according to a study in the journal Ethology Ecology and Evolution.

Some birds, like egrets, actually choose to nest around crocodile and alligator hangouts because they offer some protection from tree-climbing predators like raccoons, snakes and monkeys. There’s a blood price, however. Chicks and sometimes adult birds will become snacks for the crocodilians if they venture too close.

While on a research trip to Madras Crocodile Bank in Tamil Nadu, India, lead author Vladimir Dinets of the University of Tennessee noticed that mugger crocodiles seemed to be balancing twigs on their snouts.

“The crocodiles remained perfectly still for hours, and if they did move to change position, they did it in such a way that the sticks remained balanced on their snouts,” according to the paper.

Then, as an egret came close and leaned over to grab a stick, the crocodile suddenly lunged. The bird barely escaped with its life.

The study’s two other coauthors noticed similar behavior over 13 years working at St. Augustine Alligator Farm Zoological Park in Florida.

Were the sticks purely there by coincidence? Was it just part of the camouflage? Or could these reptiles actually be using these sticks as lures?

After studying the habits of these reptiles at four sites in Louisiana for a year, the scientists confirmed that alligators and crocodiles do indeed use twigs to lure unsuspecting birds to their doom.

Here was the really strange part: The reptiles were covering their snouts with sticks only during spring nesting season, when demand for twigs was high and birds would grab every little woody scrap they could get their beaks on to build their nests.

Birds will get into nasty fights over these valuable building materials, and even steal twigs from one another. If a camouflaged crocodile or alligator had a stick on its snout, chances are a foolish bird would make a go for it.

So the crocodilians were not just clever enough to use lures, they were also aware enough of bird behavior to know exactly when their bait would be useful.

“Use of objects as hunting lures is very rare among animals, being known to date only in captive capuchin monkeys, a few bird species and one insect,” the authors wrote.

It's indeed a rare skill indicative of complex behavior. And because crocodilians as a group have been around since the time of the dinosaurs, the scientists think it could also shed light on their long-extinct relatives. Predatory dinosaurs might have been much smarter — and thus, perhaps even scarier — than we currently believe.

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