Their pendulous noses and pot-bellied stomachs may seem outlandish but are useful adaptations to their swamp surroundings. Their ‘paunches’ contain an array of bacteria, which help break down plant cellulose and deactivate the toxins in some of the leaves. The protruding nose of the males helps resonate their calls through the forest. The bigger the nose, the more attractive he is to females! It grows so big he has to push it aside while feeding.

Primarily arboreal, they are never more than 600 m from a river. They move through the trees using all four limbs and will leap out of the trees into the water. They are capable of swimming 20 m underwater. They may cross rivers by swimming if alone or they may cross by jumping from a tree on one bank to one on the other side at narrow points of the river if in a group. Webbing between their digits aids them in swimming.

Very few zoos have proboscis monkeys because of their special dietary needs. The monkeys are picky eaters – they eat leaves from certain plants only, and only shoots and young leaves. Our keepers provide the proboscis monkeys with 80kg of fresh leaves daily to pick and choose. The leaves are collected from three to four different plant species around the Zoo. For a balanced diet, ‘toppings’ such as primate pellets, corn, fruits and vegetables are added to the ‘salad’.