Proboscis monkeys have the longest noses of all primates. In elderly animals, it can reach 17.5cm (a quarter of the body length) Although its function is not known for sure, it is likely to be a visual signal used in mate choice. The male vocalises through the nose with a kee honk sound.

Subspecies
None.

Life span
13.5 years.

Statistics
Head and body length: Female: 61-64cm, Male: 73-76cm. Tail length: Female: 55-62cm, Male: 66-67 cm. Weight: Female: 10kg Male: 21kg

Physical description
Males have an elongated pendulous nose. The shoulders, cheeks, throat and nape are pale orange with a red-orange crown and back, and the legs, belly, rump patch and tail are white-grey. Adults have pink faces, but juveniles have a blue face until the age of three. The feet are partially webbed, probably as an adaptation for swimming. Proboscis monkeys move quadrupedally.

Distribution
Proboscis monkeys inhabit Borneo.

Habitat
They live in mangrove, lowland, riverine and swamp forest.

Diet
Proboscis monkeys feed on leaves, seeds, fruits, flowers and a very small proportion of animal prey.

Behaviour
Typical group size ranges from 4-20 (average of 9) members. Troops may be all-male bachelor groups, or will only have one male and numerous females. Troops are not territorial. Proboscis monkeys are diurnal and arboreal. They are expert swimmers, and the whole troop will dive into water if they are startled.

Reproduction
After a gestation period of 166 days, females give birth to one infant.

Conservation status
Proboscis monkeys are listed as Endangered by the 2000 IUCN Red List.