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Sloths spend nearly their entire lives hanging upside down in trees. Surprisingly, they usually climb down to the ground only about once a week to relieve themselves. This journey is risky because sloths are much slower and more vulnerable to predators on the ground.
Scientists are still studying why they don't simply stay in the trees for this behavior. Despite their slow movement, sloths are excellent swimmers and can cross rivers with ease.
© Smithsonian's National Zoo and Conservation Biology Institute