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Proboscis monkey

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The proboscis monkey, known scientifically as Nasalis larvatus, is a large primate native to Asia. It is an arboreal species, meaning it spends much of its life in trees. This monkey is famous for its large, fleshy nose, which is called a proboscis. It is endemic to the island of Borneo, which is shared by Brunei, Indonesia, and Malaysia. Because it is found only in this specific location, it is a very special part of the island's ecosystem.

Proboscis monkey (Nasalis larvatus) composite
Proboscis monkey (Nasalis larvatus) composite

The biology of the proboscis monkey is defined by significant sexual dimorphism. This means that males and females look very different from one another. Males are much larger than females. A male can reach a weight of 30 kilograms, while females are smaller. The most striking difference is the male's nose. A male's proboscis can exceed 10 centimeters in length and hangs below the mouth. Scientists believe this feature is a result of sexual selection. A larger nose may help males produce louder vocalizations to attract females. The skull of the monkey has specialized nasal cartilages to support this large structure.

Both sexes possess a distinctive bulging stomach, often called a pot belly. This shape is related to their specialized diet. They are seasonal folivores and frugivores, meaning they eat mostly leaves and fruit. They consume at least 55 different plant species. Their eating habits change with the seasons. From January to May, they focus on eating fruit. From June to December, they eat mostly leaves. They even chew their cud to digest their food more efficiently.

011191 00001 Nasenaffen am Kinabatangan
011191 00001 Nasenaffen am Kinabatangan

Proboscis monkeys are highly adapted to life near water. They are considered perhaps the most aquatic of all primates. They are capable of swimming up to 20 meters underwater. They often swim across rivers to move between areas. While they are excellent swimmers, they are also arboreal. They move through the trees by leaping and moving on all fours. They may even jump off branches to descend directly into the water. They generally stay within one kilometer of a water source. This proximity helps them find food and navigate their habitat.

Socially, these monkeys live in a complex fission-fusion society. This means their group sizes change frequently. They often live in groups consisting of one adult male, several females, and their offspring. These groups usually contain between 3 and 19 individuals. However, they can join together into larger bands of up to 60 individuals. These bands often gather at specific sleeping sites as night falls. While they travel together during the day, individuals only play and groom with members of their own specific group.

Proboscis monkey (Nasalis larvatus) composite
Proboscis monkey (Nasalis larvatus) composite

History shows that Westerners first learned about this species through Baron Friedrich von Wurmb. In 1781, he made the monkey known to the West. He later sent specimens to Stamford Raffles in Europe. The genus name, Nasalis, comes from the Latin word "nasus," meaning nose. Today, the species is divided into two subspecies. The most common is N. l. larvatus, which lives across most of Borneo. The other is N. l. orientalis, which is restricted to northeast Kalimantan. Some scientists do not even recognize the second subspecies as separate.

Currently, the proboscis monkey is an endangered species. Their population decreased by more than 50% in the 36 to 40 years leading up to 2008. This decline is caused by habitat loss from logging and the creation of oil palm plantations. Hunting is also a threat because the monkey is sometimes treated as a delicacy or used in traditional medicine. They face natural predators as well, including crocodiles, clouded leopards, and large eagles. To help protect them, they are legally protected in all regions of Borneo and live in 16 different protected areas.

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File:Proboscis monkey (Nasalis larvatus) composite.jpg
Proboscis monkey (Nasalis larvatus) composite.jpg
File:011191 00001 Nasenaffen am Kinabatangan.jpg
011191 00001 Nasenaffen am Kinabatangan.jpg
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