Sloth guts: They're made for hanging

Three-toed sloths have a unique abdominal design; their innards are fixed to their lower ribs to avoid squashing the lungs while hanging upside down, a study has found.

The South and Central American forest dweller, also known as the brown-throated sloth, spends a large part of its life hanging from its hind legs to reach young, tender leaves growing on the tips of branches, as well as to groom.