Among the greatest mysteries of the tropical rainforest are the pooping habits of sloths. Really. Those furry, slow-moving tree dwellers almost never descend from the safety of the tree tops—except ...

For years scientists assumed that sloths don't fart — believing the methane produced by their slow digestive system was simply absorbed into their bloodstreams and breathed out through their mouths.

Defecating exposes sloths to predators on the jungle floor. An unexpected ally benefits, and returns the favor. A brown-throated three-toed sloth peers over a tree's buttress root while defecating on ...