Watching spider monkeys play is a delight. A youngster will watch an adult’s tail, suddenly bite it and run away. In return, adults sometimes chastise the young with a slap. On occasion, all play a kind of tag in which they chase an individual until it is caught, the runs off after the others in hot pursuit until it manages a grab or a playful bite. And so it will go on.

Having an amazingly sensitive gripping tail is totally unique to these monkeys.

 The spider monkeys use their tail as an extra limb and this makes swinging through the branches look easy,

 Their curious tails even have a bare patch of skin at the tip, much like a palm of a hand, for a more precise grip. But most importantly of all, the monkeys have tails so powerful they can support their own body weight.

 But these monkeys have another special adaptation for moving through the jungle. Their hands have no thumbs at all.

Some trees have a most peculiar effect on those that visit them. The web of life in forests are so complex that we still do not understand all that is going on. But there is one creature enlisted by the trees whose life is so closely entwined that many forest trees would disappear without its cooperation.

Through their role in seed dispersal, spider monkeys have a capacity to help regenerate rainforests. It is believed that some seeds, like dialium, rely on being passed through a spider monkey’s stomach in order to regenerate.

Hanging by long tails from a high branch it is easy to see the black spider shape that's prompted the forest Indians to give the monkey its name. Spider monkeys spend their whole lives high up in the rainforest canopy eating fruit but as with everything it is not that simple. Their prehensile tail is the longest in the world.