Many predators have built-in lures for tricking prey. Snapping turtles' tongues look like worms. Anglerfish grow glowing protrusions that lure smaller first directly towards their mouths. It is the truly clever predator, however, that uses tools fashioned from the environment to snag a meal. Chimps use sticks to harvest ants, dolphins use sponges to stir up the seafloor and, researchers have now discovered, mugger crocodiles balance sticks and twigs across their snouts—just around breeding season for water birds.
Working in India, the researchers observed that the crocs would situate themselves in shallow waters near the shore and do their best impression of a log. When the unsuspecting birds waded too close—presumably enticed by those nice sticks, perfect for nest-making—the crocs would lunge.
To verify whether these actions spanned species and were timed to the birds' breeding season, the researchers set up observation stations of American alligators in Louisiana. Wired explains what they saw:
The researchers found that the occurrence of sticks on crocodilians was not random. It was more often seen in those reptiles living near the bird nests and was only witnessed during the nesting season. Of course, it could be that floating sticks randomly find themselves atop a croc's nose, but the researchers say that floating sticks are extremely rare in the waters observed. This means that it's more likely that the reptiles are deliberately collecting and using the twigs as bait. If this is the case, it would be described as tool use.
While crocodiles and alligators are stereotypically seen as "lethargic, stupid and boring," study author Vladimir Dinets says, he hopes their newly discovered tool-using skills will bring greater appreciation to the cunning crocodilians.
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