The most brilliantly coloured of all mammals are our relatives the monkeys. The scarlet face of a Uakari and bright blue bottom of a Mandrill, are matchless. But colour-vision first gave this group another advantage up in the trees - finding ripe fruits and leaves. Hanging from a rope high in the canopy of Venezuela, Sir David watches brilliantly-coloured red howler monkeys use their sharp eyes to pick only the best leaves, before seeing off their rivals with one of the loudest sounds in nature. Acute vision and a lively intelligence allows the capuchin monkey to eat clams in the swamps of Costa Rica. A group crack-open shellfish on their favourite tree-anvil as Sir David commentates. The swamps are also full of insects, but the monkeys rub themselves with a special plant that repels them. The only nocturnal monkey is caught in David's torch beam. Far from losing it's reliance on vision, the Douracouli, or Owl monkey, compensates with enormous eyes and reserves social activity for moonlit nights. In the dim light of the West Africa forest beautiful guenon monkeys send messages to each other with colourful face patterns. These forests are full of eagles, leopards and chimps, but the guenons have an extraordinary anti-predator alliance to deal with them. Communication in monkeys goes way beyond simple colour signals though. These intelligent mammals often live in large groups - where the socially skilled excel. When toque macaque monkeys battle for mates, we see how brain can triumph over brawn. A change in climate forced one group of African monkeys down from the trees and on to the grasslands. But living on the ground brought an increased risk from predators, forcing baboons to live in larger groups where social skills became even more important. Life on the ground also opened up new hunting opportunities - the hapless flamingos of Kenya are now on the menu.