Saturday, February 22, 2014

Tree climbing crocs

An American alligator perches in a 
tree  in the Pearl River Delta, Mississippi. 
Photo credit: Kristine Gingras, courtesy 
of  University of Tennessee
Two species of paleo crocodilians (Mekosuchus inexpectatus  and Trilophosuchus rackhami) have been hypothesized to have been arboreal, they share a  small body size and have a lighter build than most other crocs and have been commonly referred to as "drop crocs."

Now, Vladimir Dinets and colleagues (2014) review the evidence that living species of crocodilians can and do climb into trees, a behavior overlooked by science until now.

People around the world have observed and photographed the arboreal abilities of many crocodilian species, but herpetologists hadn’t studied the behavior. Now, research documented tree-climbing Australian freshwater crocodiles, American crocodiles, Central African slender-snouted crocodiles and Nile crocodiles. The paper also presented anecdotal reports of many other croc species taking to the trees.

The crocs weren’t just clambering onto easily reached low branches. The animals could climb vertical trunks. Sometimes climbing all the way to the trees’ crown.

Most of the tree-climbers  were young and still relatively small, two meters (6.5 feet) or less in length. The animals may have been climbing the trees to bask in the sun, since the areas where the animals were observed in trees often lacked other suitable sun bathing locations, noted the study’s authors.

The slender-snouted crocodile of central Africa is quite adept at arboreal behavior. They  roosted on branches both night and day. One specimen climbed though a tangle of branches to rest on a branch five meters from the river bank and four meters above the water.

With some of the species examined the ability to climb decreases with increasing size and mass. Hatchlings are lightweight and can even climb vertical brickwork . In the  wild, Australian freshwater crocodiles frequently climb into low branches above the water, either by climbing directly onto the tree close to the water, or by climbing onto the tree from the bank and then along a branch.

The authors note that the ability to climb vertically reflects crocodilians’  spectacular agility on land and their ability to pull the body along an angled surface. And, that the degree of arboreality of extinct crocodilians and many other Archosaurian taxa cannot always be ascertained from fossil material. Any small, highly terrestrial crocodilian, such as the recently extinct Trilophosuchus rackhami could have been be arboreal to some extent.

Citation
Dinets V, Britton A, Shirley M. 2014. Climbing behaviour in extant crocodiles. Herpetological Notes 7:3-7.

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