Science

Wily Crocs climb trees for vantage point and thermoregulation

A team of biologists from the University of Tennessee, led by Dr Vladimir Dinets, have made an interesting discovery about crocodiles after conducting the first thorough study on their basking and tree climbing behaviour. The results suggest those living in areas home to crocodiles may need to be more careful than before.

The team found that four species of crocodile can climb trees, despite not showing any obvious morphological adaptations necessary to do so; these species are the American crocodile (Crocodylus acutus), Australian freshwater crocodile (Crocodylus johnstoni), Central African Slender-Snouted crocodile (Mecistops cataphractus) and the Nile crocodile (Crocodylus niloticus).

Each crocodile species was observed climbing trees above water, but how far up the trees or along the branches they ventured depended on their size. Smaller crocodilians were able to climb higher and farther than larger ones, and had been observed as high as four meters up a tree, and five meters along a branch.

In Everglades National Park in the United States, American crocodiles up to 1 meter long were observed lying on aerial roots and low branches of mangrove trees during the day.

The scientists also observed a 2 meter long Nile crocodile in the Okavango Delta, Botswanna, basking on a tree approximately 0.5 meters above the surface of the water. The crocodile dropped into the water from the branch as the team passed by in a boat, and it is assumed the croc probably climbed up onto the branch from the point where the tree dipped into the water near the bank of the river.

Australian freshwater crocodiles were observed climbing steep river banks, and even attempting to climb chain link fences up to 1.8 meters tall. Dr Dinets, who is the lead author of the paper stated: “Climbing a steep hill or steep branch is mechanically similar, assuming the branch is wide enough to walk on. Still, the ability to climb vertically is a measure of crocodiles’ spectacular agility on land.”

Crocodiles that were seen climbing trees by the team appeared very nervous of being recognised, jumping or falling into the water when an observer was as far as 10 meters away. This response led Dr Dinets and his co-authors to believe that the tree climbing and subsequent basking behaviours of crocodiles are driven by thermoregulation and the surveillance of habitat.

“The most frequent observations of tree basking were in areas where there were few places to bask on the ground,” reported Dr Dinets, “implying that the individuals needed alternatives for regulating their body temperature. Likewise their wary nature suggests that climbing leads to improved site surveillance of potential threats and prey”.

Jack Di Francesco

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