Sloth’s Strange Walk Is Really Just Upside Down

Two-toed sloths spend a lot of time hanging upside down from tropical tree branches in Central and South America, and looking very odd. But new research suggests they move just like a mirror image of many upright four-legged creatures.

Mammals seem to move their legs in very standardized fashion during locomotion, whether walking on land, on branches or suspended under branches.  What differs is the way muscles are arranged and attached, which can completely alter the functionality of limbs.

Sloths don’t grasp branches but instead suspend themselves from tree limbs with long, hook-like claws on their sideways-oriented hands and feet. Given how weird sloths are, it seemed possible they may have evolved a different way of moving from other mammals.

To investigate whether strange anatomy translated to strange locomotion, scientists used video and x-rays to see inside sloths as they moved along a wooden pole and a motorized “treadpole” they were trained to move along for a snack.

They found that the sloths didn’t simply lumber along the branches at a slow-and-steady pace.  Their velocity varied, and they used several different gaits while moving. In the “exploratory gait,” the sloths assumed an inverted crouch position in which they held their nose close to the pole, while in the “traveling gait” they extended their arms further to increase their stride.

Read more in the original article here.