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They live their lives upside down; instead of defying the force of gravity in an upright position, sloths spend most of their lives hanging in trees upside down. If they have to move, they do so only slowly. Very slowly. But why are sloths so 'lazy'? And how has the locomotive system of these outsiders adapted to their unhurried lifestyle in the course of evolution? Zoologists of the Friedrich Schiller University Jena (Germany) have looked into the matter comprehensively.
"To our great surprise the locomotion of the sloths is basically not so different from the locomotion of other mammals, like monkeys for instance, which instead of hanging from tree branches, balance along them", says Dr. John Nyakatura. In his doctoral thesis at the Institute of Systematic Zoology and Evolutionary Biology with Phyletic Museum the evolutionary biologist analyzed the locomotion of sloths with X-ray video equipment. That was not so easy at the beginning, as the first sloth stepping in front of the camera for the Jena scientist simply refused to work. "Mats, the sloth, just didn't want to co-operate", Nyakatura remembers, smiling. Therefore it was given to a zoo and made headlines around the globe as the 'laziest animal in the world'.
In comparison, the two-toed sloths Julius, Evita and Lisa appeared to be more co-operative. They brachiated along the provided pole in the X-ray tube. "The position of their legs and the bending of their joints matches exactly those of other mammals in the process of walking", Nyakatura explains. Hence one could imagine the locomotion of sloths actually as 'walking' under a tree. Just much slower than other quadrupeds.
However, the evolutionary biologist found distinct differences in the anatomical structure of the animals. "Sloths have very long arms, but only very short shoulder blades (scapu
|Contact: Axel Burchardt|