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Table of Contents
The proboscis monkey (Nasalis larvatus), often known as the long-nosed monkey, is an Old World monkey with a huge nose, reddish-brown skin, and a lengthy tail. This species coexists with Bornean orangutans and silvery lutung monkeys.
See the fact file below for more information on Proboscis Monkey, or you can download our 30-page Proboscis Monkey worksheet pack to utilize within the classroom or home environment.
Key Facts & Information
DESCRIPTION
- The proboscis monkey is a giant species, and one of Asia‘s largest monkey species. Only the Tibetan macaque and a few gray langurs can compete with its size.
- The animal exhibits significant sexual dimorphism. Males have a head-body size of 66–76.2 cm (26.0–30.0 in) and weigh 16–22.5 kg (35–50 lb), with the largest known weight of 30 kg (66 lb).
- Females have a head-and-body length of 53.3 to 62 cm (21.0 to 24.4 inches) and weigh 7 to 12 kilograms (15 to 26 lb), with the largest known mass of 15 kg (33 lb). The large nose or proboscis of the male, which can exceed 10.2 cm (4.0 in) in height and hangs lower than the mouth, contributes to dimorphism.
- Theories for their long noses include sexual selection by females who like louder vocalizations, with the size of the nose enhancing the volume of the call. In females, the nose is smaller, and in the young, it is upturned.
- Nonetheless, the female’s snout is enormous for a monkey. The proboscis monkey’s skull contains unique nasal cartilages that handle the extended nose.
- The proboscis monkey has a long coat with vivid orange, reddish brown hair on the back. The underfur is light gray, yellowish, grayish, or light orange. The fur around the pelvis and tail is white.
- Infants are born with a blue face that darkens to gray after 2.5 months. By 8.5 months of age, the look has taken on the color of adults.
- Males have a crimson penis and a black scrotum. Both sexes have protruding abdomens that give the appearance of a pot belly. The toes of several of the monkeys are webbed.
BEHAVIOR
- Proboscis monkeys live in groups with one adult male, many adult females, and their young. There may be all-male groups as well.
- Some individuals, primarily males, live alone. In a fission-fusion population, monkey groups reside in overlapping home ranges with low territoriality, with groups convening at sleeping areas when night falls.
- Bands form when groups get together and then split up, although groups can also combine to breed and groom. During the day, groups congregate and move together, but individuals only groom and engage with those in their group.
- One-male groups can have 9 to 19 members, whereas bands can have up to 60 members. One-male groups typically include three to 12 members but can have more.
- Profound hostility among monkeys is unusual, although slight aggressiveness does occur. Members of the same band often accept one another, and females have a hierarchical dominance structure.
- Males in one-male groups can stick together for six to eight years. Replacements in resident males appear to happen without much ado. Males abandon their birth groups and join all-male communities when they reach maturity.
- Females may also leave their natal groups to prevent infanticide or overbreeding, lessen rivalry for food, or advance in social position.
- Proboscis monkeys have been reported in mixed-species groups with silvery lutung in Sabah, Malaysia, including interspecific mating and a probable hybrid. Researchers believe this is due to the two species being limited to a tiny stretch of riverine woodland due to deforestation to establish oil palm plants.
HABITS AND LIFESTYLE
- Proboscis monkeys are highly sociable creatures that create armies of 2-30 animals, with a single dominant male and many (up to 10) females and their progeny.
- Males protect their group by showing their teeth and generating loud, honking signals, whereas females forage and care for the young.
- These groups may occasionally form more enormous aggregations in situations with enough food or near water. During this time, groups of proboscis monkeys relax and sleep among the mangroves on the water’s edge.
- Freshwater bodies, such as marshes or rivers, are essential for these species’ survival. Proboscis monkeys are skilled swimmers.
- They may also do deep dives while foraging or running from a threat. Proboscis monkeys interact with one another using a variety of vocalizations.
- Males will honk while claiming the group’s status and generate warning cries to signify danger. Both sexes make threat calls, but they are not the same.
- Furthermore, when angered, females and immature specimens will produce so-called “female sounds.” These monkeys will also create honking, roaring, and snarling sounds. Nonverbal signs include leaping-branch shaking and open-mouth threats with exposed fangs.
RANGE AND HABITAT
- The proboscis monkey is unique to Borneo and can be found in all three countries that border the island: Brunei, Indonesia, and Malaysia.
- It is prevalent around rivers and at the seaside. This species is limited to lowland environments subject to tides. Dipterocarp, mangrove, and riverine forests are preferred habitats.
- It’s also found in swamp woods, limestone hill forests, Nypa wetlands, ni bong marshes, and cliffs.
- This species often remains within a kilometer of a water supply. It is the most aquatic of the primates and a somewhat excellent swimmer, skilled at swimming up to 20 meters (66 feet) underwater. It has been observed swimming across rivers.
- Aside from that, the proboscis monkey is primarily arboreal, moving quadrupedally and via jumps. It has been observed jumping off trees and diving into the water.
FEEDING ACTIVITIES
- The proboscis monkey is a seasonal folivore and frugivore that mostly consumes fruit and leaves.
- To a lesser extent, it also consumes flowers, seeds, and insects. At least 55 plant species are ingested, with “a clear predilection for Eugenia sp., Ganua motleyana, and Lophopetalum javanicum.”
- Unripe fruits are favored over ripe fruits, while young leaves are chosen over mature leaves. The proboscis monkey is a seasonal eater, eating primarily fruit from January to May and mostly leaves from June to December.
- Typically, groups sleep in nearby trees. If there are rivers nearby, monkeys will sleep near them.
- Proboscis monkeys forage early in the morning and then rest further inland. They spend their days relaxing, traveling, eating, and remaining watchful. They chew their cuds on occasion to improve digestion and intake of food.
- The monkeys return to the river to scavenge once again as darkness falls.
- Saltwater crocodiles, leopards, pythons, eagles, and monitor lizards are prospective or proven predators of the proboscis monkey. If feasible, monkeys will cross rivers at narrows or arboreally and might use them to evade predators.
MATING HABITS
- In proboscis monkeys, the dominant male mates with females in a polygynous sexual arrangement. From February through November, they breed.
- The gestation period lasts 166 days and produces one infant, usually at night.
- The newborn has a bright blue face and light, nearly black coat, which changes color after 3-4 months. Females in a troop assist raise each other’s offspring, which is frequent in this species.
- They may even breastfeed the young of another female when necessary. The newborn always remains with its mother during the first year of its existence.
- However, the female quickly has another baby, and young females typically stay with their natal group while males disperse, forming all-male bachelor groups.
- Females reach reproductive maturity at four years, whereas males reach reproductive maturity at 4-5.
CONSERVATION
- The loss of natural habitat due to forest fires and the chopping of mangrove forests growing along riverbanks is now the greatest danger to this species.
- Meanwhile, coastal monkeys are losing habitat due to the expansion of human settlements and prawn farms. Another vital worry is localized food hunting and intestinal bezoar stones in traditional medicine.
- This vulnerability is exacerbated by these creatures’ gentle character, which makes them “easy prey for hunters.”
- According to the International Union for Conservation of Nature (IUCN) Red List and other sources, the population of proboscis monkeys is unknown.
- However, specific populations have been estimated in the following areas, according to the IUCN Red List: Indonesia – population numbers in this country are associated with past, and current threats, ranging from less than 100 to over 1,000 individuals.
- While Sarawak – population in this area is estimated to be less than 1,000 proboscis monkeys.
- The population of proboscis monkeys is declining, and the animals are listed as Endangered (EN) on the IUCN Red List.
Proboscis Monkey Worksheets
This is a fantastic bundle that includes everything you need to know about Proboscis Monkey across 30 in-depth pages. These are ready-to-use worksheets that are perfect for teaching kids about Proboscis Monkey, which is an Old World monkey with a huge nose, reddish-brown skin, and a lengthy tail.
Complete List of Included Worksheets
Below is a list of all the worksheets included in this document.
- Proboscis Monkey Facts
- Proboscis Jigsaw
- Same Difference
- The Three Primates
- Meet the Proboscis Monkey
- Proboscis Lifestyle
- Proboscis Habitat
- Proboscis Mating
- Folivore, Frugivore
- Proboscis Word Scramble
- Conserving Proboscis Monkeys
Frequently Asked Questions
Why is the proboscis monkey’s nose so big?
Male proboscis monkeys have significantly larger noses than other primates, which is an effective cue for both attracting mates and determining social status.
Why do proboscis monkeys have large stomachs?
Proboscis monkeys are most known for their large stomachs, something that is a direct result of both their diet and digestive system. These monkeys are choosy about what they eat and have a specific type of stomach that allows them to consume items other primates cannot digest.
How fast can a proboscis monkey run?
The proboscis monkey is a fast animal. It can run up to 15 miles per hour.
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