Spider monkeys are large New World monkeys that live in tropical rainforests from central Mexico in the north to Bolivia in the south. There are seven species of these agile primates, which get their name from the way their long limbs and tails resemble spider legs as they dangle from branches and swing through the treetops. Four long fingers on each hand help them grasp branches, too. (They also have thumbs but those are extremely short.) Their tree-to-tree locomotion, called brachiation, is how these swingers get around.

The spider monkey’s tail is prehensile, which means “capable of grasping.” It is generally longer than the animal’s body and acts as a fifth limb—an adaptation to life