By Mary Bates
You might think of crocodiles lurking in the water or perhaps sunning themselves on a riverbank, but it turns out these toothy reptiles’ domain extends to the upper branches of trees.
A new study in Herpetology Notes documents the surprisingly common tree-climbing behavior in crocodiles and their close cousins, alligators. Even without any special anatomic adaptations for gripping branches, crocodiles often make their way up trees, sometimes going as high as the crown and out onto large limbs.
Vladimir Dinets, a research assistant professor at the University of Tennessee, Knoxville, and lead author of the paper, said it didn’t occur to him to look for crocodiles overhead. But in the course of researching the reptiles’ natural behaviors, he and his colleagues noticed a number of the animals in trees and became curious. On three continents—North America, Africa, and Australia—they observed four different species climbing trees.
Dinets and his fellow researchers combed the scientific literature and found only three scientific reports describing tree-climbing crocodiles, but they discovered several anecdotal accounts by people living near crocodilian habitat.
“People who work or live around crocodiles knew about this behavior,” says Dinets. “It’s really common, but nobody outside the crocodile research community was aware of it.”
But, he says, “there’s no reason to think this behavior is new. In fact, there is some evidence that some extinct crocodilians were even more adapted to climb trees than the species alive today.”
The researchers believe the climbing is driven by two factors: thermoregulation and surveillance of the environment. Crocodiles took to the trees most frequently in areas where there were few places to bask on the ground, suggesting that the behavior is a means for regulating body temperature. And the reptiles were quick to fall or jump into the water if the researchers approached them. This skittish response implies they climb to gain a better perspective of potential threats and prey.
Christopher Gomez, an alligator hunting guide in Louisiana, says that though he’s never seen an alligator up a tree, the behavior doesn’t surprise him. “They’re really fast and maneuverable on land,” he says. “And knowing that they’re strong enough to take down large prey and drag them underwater, I’d say they’re strong enough to climb trees.”
Although crocodilians have an ancient lineage, dating back to the time of the dinosaurs, and are well known to humans, they’re still surprising us. In 2013, Dinets and his colleagues reported that alligators and crocodiles use sticks as lures to attract birds looking for nesting material. The reptiles lie in the water beneath bird colonies with sticks resting on their noses, ready to snap when a bird gets too close.