Colobus monkeys spend almost their whole life in the trees. They can leap distances of 15 metres from one branch to another - more than the length of a school bus. Their long white tails act like rudders, helping them steer in mid-air.
Unusually for monkeys, they have no thumbs on their hands - just four fingers. Their name 'colobus' comes from a Greek word meaning 'shortened'. Scientists think losing the thumb helped them swing through branches faster, like four hooks instead of five.
Colobus monkeys eat mostly leaves - even tough, hard-to-digest ones that other animals can't manage. Their stomachs are made of several compartments, a bit like a cow's, so they can break down the leaves slowly over many hours.
Babies are born pure white - no black at all. They get cared for by their mum, their aunties, and their older sisters, all passing the baby gently around. The white fades to black over a few months. Watching a tree full of colobus monkeys - with one snowy white baby in the middle - is one of the great sights of an Ethiopian forest.