Proboscis Monkeys: Endemic Animals of Indonesia that are Almost Extinct

Indonesia ranks second in the world for terrestrial biodiversity richness, and when marine biodiversity is included, it is the top country. According to LIPI data from 2017, Indonesia has 17% of the world's total species, with approximately 35-40 thousand species of plants (11-15%), 707 species of mammals (12%), 350 species of amphibians and reptiles (15%), and 1,602 species of birds (17%). Its freshwater fish population includes 2,184 species (37%), and its marine biodiversity boasts at least 2,500 species of molluscs, 2,000 species of crustaceans, 6 species of sea turtles, 30 species of marine mammals, and over 2,500 species of fish.

Indonesia, being a country with high biodiversity in the world, has many native animal species that are unique to Indonesia or only naturally occur in certain regions, known as endemic animals.

Indonesia, with its high biodiversity, is home to a wide range of animal species. Among them, there are those that are native only to Indonesia, known as endemic animals, which naturally inhabit certain areas and cannot be found in other areas.

There are several animal species that are endemic to Indonesia, such as the Sumatran tiger, Sumatran rhinoceros, orangutan, Kalimantan elephant, Bali starling, Komodo dragon, maleo bird, bird of paradise, and dwarf tarsier.

 

 

Indonesia, being an archipelagic country, possesses a rich biodiversity of flora and fauna that is both unique and fascinating to study. One such example is the Proboscis Monkey, a primate species found exclusively in Indonesia. The Proboscis Monkey is easily recognizable due to its distinctive nose shape, which is long and large. In addition to this, it also has a bulging stomach caused by its unbalanced diet. Apart from fruits and seeds, the Proboscis Monkey also feeds on leaves. Its habitat is primarily in wetland areas such as mangrove forests, riverbanks, riparian forests, fresh water swamps, and peat swamps. The Proboscis Monkey is widespread in the forests surrounding estuaries or river banks in Kalimantan. The species has several names given to it by the locals of the island of Borneo, including "Pika," "Dutch Monkey," "Raseng," "Bahara Bentangan," and "Kahau."

Proboscis monkeys are arboreal creatures that typically inhabit trees but may occasionally descend to the forest floor. They move from branch to branch using a variety of techniques, including jumping, hanging, and walking on all fours. Moreover, proboscis monkeys are highly adept swimmers due to the webbing between their fingers and toes, similar to that of frogs, enabling them to cross rivers with ease. These primates are diurnal, meaning that they are active during the day and rest at night. In the afternoon, proboscis monkeys usually seek out trees to sleep in along riverbanks. They often congregate in one tree or several trees located in close proximity to one another.

The proboscis monkey population is in danger of extinction due to the destruction and disturbance of their habitat resulting from land conversion and forest destruction. Illegal hunting has also contributed to the decline in their numbers.

The Proboscis Monkey is classified as Endangered by the IUCN Redlist and is listed in Appendix I of CITES, which prohibits their trade. These primates are thus safeguarded under international regulations.

The Proboscis Monkey, which is exclusively found on the island of Borneo, is recognized for its distinctive facial features, specifically its elongated nose. However, not all individuals of this primate species possess long noses. It is only the male Proboscis Monkeys with the scientific name Navalis larvatus that exhibit this characteristic nose which has earned them their nickname "long-nosed monkey".

The reason why only male Proboscis Monkeys possess elongated noses and its specific function still remain uncertain. However, it is suggested that the development of this feature is due to natural selection. Interestingly, the male's enlarged nose is considered an attractive trait to female monkeys, as they tend to prefer males with larger noses as their partners.

Male Proboscis Monkeys are physically larger than females, with a maximum size of 75 cm and weight of 24 kg. In contrast, female Proboscis Monkeys measure around 60 cm and weigh approximately 12 kg. Both male and female Proboscis Monkeys share the same reddish-brown dominant fur color.

Upon observation, Proboscis Monkeys are noticed to have an enlarged stomach. According to reports from Tnsebangau, this distended stomach is attributed to their feeding habits. In addition to consuming fruits and seeds, these primates also feed on leaves that produce a significant amount of gas during digestion.

Apart from consuming plant-based foods, Proboscis Monkeys frequently feed on various types of insects. During low tide, these primates typically come down from trees to search for insects on the ground. Despite their arboreal nature, spending a considerable amount of time in trees, Proboscis Monkeys have shown proficiency in swimming.

Proboscis Monkeys possess skin membranes similar to those of frogs on their hands and feet. This unique feature enables them to be exceptional swimmers, allowing them to cross rivers and even swim from one island to another.

 

The proboscis monkey (Nasalis larvatus) is a unique species of long-nosed monkey with reddish-brown hair, and is one of the two species in the Nasalis genus. Endemic to the island of Borneo, they can be found scattered across mangrove forests, swamps, and coastal forests. The distinctive feature that sets the proboscis monkey apart from other primates is the long and large nose, which is only present in males.

This primate holds a special place in the identity of South Kalimantan province and is known by various names, including the proboscis monkey or long-nosed monkey in English, and the Dutch monkey, pika, bahara stretch, raseng, and kahau in local languages. Due to illegal hunting, habitat loss, and limited range, the proboscis monkey is listed as an endangered species on the IUCN Red List and is protected by both international organizations and the Indonesian government. It is also included in CITES Appendix I.

The proboscis monkey, which spends most of its time in trees, is a social species that lives in groups of between 10 and 32 individuals. The social system of proboscis monkeys is based on a one-male group, consisting of one adult male, several adult females and their young. Additionally, there is an all-male group, consisting of several male proboscis monkeys. Adolescent males leave the one-male group and join the all-male group to avoid inbreeding. Proboscis monkeys are also excellent swimmers and can be observed swimming from one island to another. The membranes between their toes support their swimming ability, and they can also dive in a few seconds. The proboscis monkey's long nose is equipped with a valve to assist with swimming.

Nasalis larvatus, or Proboscis Monkeys, can be spotted in various locations such as the Pleihari Tanah Laut Wildlife Reserve (SM), Pleihari Martapura Wildlife Reserve, Pulau Kaget Nature Reserve (CA), Gunung Kentawan CA, Sebuku Straits CA, and Kelumpang Bay. They are also sighted on the peripheries of the Barito River, Negara River, Paminggir River, Tapin River, Bakut Island, and Flower Island.

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