The brown spider monkey gets the “spider” in its name from its extremely long limbs and its gripping tail, which works like a fifth limb. It is one of the biggest and most agile monkeys of the Americas. Its tail can hold up its whole body, and it is so precise that it can pick up something as small as a peanut. It lives in mixed groups of up to about twenty, which split into smaller, changing groups during the day. Its call carries a long way and helps the group stay together in the thick treetops. It is Critically Endangered, and fewer than 1,000 adults are thought to be left.