For the first time, crocodilians have been shown to use tools. University of Tennessee professor Vladamir Dinets observed two different groups of the reptiles—American alligators in Louisiana and mugger crocodiles from the Asian subcontinent—positioning sticks and twigs on their snouts.
With tools in place, they'd stay very still in order to tempt birds that were building nests. When an unfortunate egret or heron reached for the convenient nearby stick, the reptiles would lunge.
A well-camouflaged mugger crocodile in stick-displaying behavior. Madras Crocodile Bank, Tamil Nadu, India. via
While tool-use has been observed among primates and more intelligent birds, Dinet’s research, published in Ethology Ecology & Evolution, is the first documented case of reptiles doing so. What’s more, the crocodiles were using the twig lures seasonally—during the March-May nest-building season—which Dinet argues is added proof that the tool use isn't random.
As interesting as the conclusion is for present crocodilians, it may also have implications for the past, dating back to the age of the dinosaurs. When I spoke with the head of the American Museum of Natural History’s Mark Norell for another story a while back, he gave me a rule of thumb: “The best way to understand anything about dinosaurs is by looking at living animals.
“If you look at characteristics that birds and crocodiles have in common, the explanation is that it is in the common ancestor that birds and crocodiles had at one time,” he said. “So then you would predict, in lieu of any other evidence, that this [shared characteristic] was present in non-avian dinosaurs. Things like how parts of the brain work, and their four-chambered heart—things that are present in birds and in crocodiles—we would predict were present in dinosaurs.”
While the definition of what constitutes “using a tool” is debated, Darren Naish at SciAm notes that there have been at least 33 families of birds observed using tools. Several of them, like crocodiles, use bait to catch prey. The green heron attracts fish to the water's surface by dropping feathers, twigs and berries into the water, and burrowing owls use mammal dung to attract dung beetles.
While it's far from conclusive on its own, observing baiting behavior in crocodile could help color in aspects of dinosaur life that are nigh impossible to discern from the fossil record. Since there's evidence of tool use in both birds and crocodilians, it's possible a common ancestor also used tools. While it's a hard thing to prove, it's an exciting possibility, and something worth looking out for.
"Our research provides a surprising insight into previously unrecognized complexity of extinct reptile behavior," said Dinets in a release. "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."
Just as the earliest artist renderings of dinosaurs showed them lumbering slowly in swamps, Dinet said that reptiles used to be viewed as “lethargic, stupid and boring.” But as his research shows, old opinions fade quickly in light of new evidence.