Old World Monkeys: Cercopithecidae

Physical characteristics: The proboscis monkey got its name from its bulbous nose, which in the male is long and drooping. It is thought that females are attracted to the large nose. The naked face is pinkish brown. The head and back are reddish orange, while the shoulders, neck, and cheeks are pale orange. The undersides, legs, and tail are grayish white. The webbed feet are useful for swimming. Males weigh about 45 pounds (20.4 kilograms) and measure about 30 inches (74.5 centimeters), with a tail length of 26.5 inches (66.5 centimeters). Females are about half the male size, weighing 21.6 pounds (9.8 kilograms) and measuring 25 inches (62 centimeters), with a tail length of 23 inches (57.5 centimeters).

Geographic range: Proboscis monkeys are found in Borneo.

Habitat: Proboscis monkeys occupy coastal mangrove forests and forests along rivers.

The proboscis monkey is found in mangrove and lowland forests in Borneo. (© Aaron Ferster/Photo Researchers, Inc. Reproduced by permission.)

Diet: Proboscis monkeys feed mainly on leaves, supplemented with flowers and seeds. They eat unripe fruits but not ripe fruits, which, when processed by stomach bacteria, can cause potentially deadly gas and acid formation.

Behavior and reproduction: A proboscis monkey family consists of an adult male and several females and their offspring. Females give birth to a single infant and are assisted by other females with childcare. Young males are usually expelled upon puberty, traveling alone for a while or joining other bachelors. Proboscis monkeys do not defend their territory, but adult males threaten intruders with loud honks using their nose.

They are arboreal and diurnal, foraging in the early morning, then taking a long rest to digest their food. They may eat again before dark. The monkeys move on all fours and brachiate through the trees. They often jump from the trees into the water, from heights of as much as 53 feet (16 meters). They swim well and can stay underwater to escape a predator. They sleep in trees with branches that extend over water, perhaps as a lookout for their main predator, the clouded leopard.

Proboscis monkeys and people: Proboscis monkeys are hunted for meat.

Conservation status: The IUCN lists the proboscis monkey as Endangered due to hunting, as well as habitat loss and degradation from logging. ∎