These crocodiles rest on trees!

A study has found that the reptiles can climb trees as far as the crowns.

When most people envision crocodiles, they think of them waddling on the ground or wading in water - not climbing trees.

"Climbing a steep hill or steep branch is mechanically similar, assuming the branch is wide enough to walk on," the authors wrote.

"Still, the ability to climb vertically is a measure of crocodiles' spectacular agility on land," said Vladimir Dinets, a research assistant professor in University of Tennessee's department of psychology.

Dinets observed crocodile species on three continents - Australia, Africa and North America - and examined previous studies and anecdotal observations.

They found that four species climbed trees - usually above water - but how far they ventured upward and outward varied by their sizes.

The smaller crocodiles were able to climb higher and further than the larger ones.

Some species were observed climbing as far as four metres high in a tree and five metres down a branch.

The crocodiles seen climbing trees, whether at night or during the day, were skittish of being recognised, jumping or falling into the water when an approaching observer was as far as 10 metres away.

This response led the researchers to believe that the tree climbing and basking are driven by two conditions - thermoregulation and surveillance of habitat.

"The most frequent observations of tree-basking were in areas where there were few places to bask on the ground, implying that the individuals needed alternatives for regulating their body temperature," the authors wrote.

The data suggests that at least some crocodile species are able to climb trees despite lacking any obvious morphological adaptations to do so.