Long-tailed arboreal primate found along rivers and in swampy mangrove jungles of Borneo.
Adults wear a coat of light brown fur that turns red around the head and shoulders and grey at the arms, legs, and tail. The underfur is light-grey, yellowish, or greyish to light-orange. Only males develop the namesake nose.
Theories for the extended length of their nose suggest it may be sexual selection by the females, who prefer louder vocalisations, with the size of the nose increasing the volume of the call. The large nose of the male is known to become red and swollen when the individual is either angry or excited.
Males have a head-body length of 66 to 76.2 cm (26.0 to 30.0 in) and typically weigh 16 to 22.5 kg (35 to 50 lbs)
Proboscis monkeys live in groups of about 20 consisting of a single male and up to a dozen females; males live in bachelor groups
Groups gather during the day and travel together, but individuals only groom and play with those in their own group. Overall, members of the same bands are fairly tolerant of each other. A linear dominance hierarchy exists between females.
Proboscis monkeys are known to make various vocalizations. When communicating the status of group, males will emit honks
They eat mainly mangrove leaves, shoots, seeds, and unripe fruits, but will occasionally consume insects as well
The Proboscis Monkey spends the majority of its life very close to water and is an adept swimmer, aided by its partially webbed feet, which help it to both paddle in the water and walk on the slippery banks.
Proboscis monkeys are the primate world’s most prolific swimmers, frequently leaping from tree limbs and hitting the water with a comical belly flop