identified by whether they have two or three claws on their front feet. Two-toed sloths are slightly bigger and tend to spend more time hanging upside-down than their three-toed cousins, who will often sit upright in the fork of a tree branch. Three-toed sloths have facial coloring that makes them look like they're always smiling. They also have two extra neck vertebrae that allow them to turn their heads almost all the way around! They rarely come down from the trees. About once every week, they descend to go to the bathroom.