Diana monkeys live in groups of up to 30 individuals and spend almost their entire lives in the upper canopy of the rainforest, leaping between branches and rarely coming down to the ground. They eat mainly fruit, leaves, and insects, and they are expert at finding food in the dense upper branches.
One of the most fascinating things about Diana monkeys is their alarm call system. They have different calls for different types of predator - one call for eagles above, another for leopards below. Other monkey species that live nearby, like red colobus monkeys, can actually understand and react to Diana monkey alarm calls. It is a kind of cross-species language.
The Diana monkey is listed as vulnerable, which means its numbers are declining and it needs protection. The biggest threat is the loss of rainforest. Diana monkeys need tall, connected forest to thrive - when forest is broken into small patches, the monkeys cannot move easily between them.