Hose’s Langur, Presbytis hosei
HOSE'S LANGUR
Presbytis hosei
Geographic Distribution and Habitat
Hose’s langurs are found throughout the northern Sarawak and Sabah regions of Malaysia, in East Kalimantan of Indonesia, and in Brunei Darussalam, all of which make up the northern part of the island of Borneo. They can be found near coastal regions and rivers, as well as in mountains. Hose’s langurs primarily call dipterocarp forests home—a common but highly variable forest type found in Borneo characterized by being primarily made up of trees from the Dipterocarpaceae family. Dipterocarps are characterized by their incredible size—emerging from the top of the forest canopy at a height of up to 197 feet (60m). The langurs will also sometimes wander into plantations, where they have been known to steal crops and even rob chicken nests, causing local people to see them as a nuisance.
Originally considered a member of the genus Semnopithecus (the gray langurs) but later, researchers realized that the Hose’s langur fits better with the surilis under the Presbytis genus. Miller’s grizzled langur and Sabah grizzled langur were once considered subspecies of the Hose’s langur but were later identified as their separate species.
Size, Weight, and Lifespan
The Hose’s langur has a head and body length of 19–22 inches (480– 560 mm) for both males and females. While only slightly sexually dimorphic compared to some other primate species, males do tend to be a bit larger weighing between 13.2 and 15.4 pounds (6.0–7.0 kg) compared to females’ 12–13.2 pounds (5.5-6.0 kg). Both males and females have a tail length of 24.6–33 inches (650 mm – 840 mm).
We don’t currently know how long Hose’s langurs live, but likely similar to other langurs that typically live 15-18 years in the wild.
Appearance
Contrasting with the light pinkish skin on the rest of their face, the Hose’s langur has blackish markings around their eyes, similar to a bandit mask. Their hair creates a point (or crest) on the top of their head which is bluish-gray in color, almost like a hat. The hair along their backs is the same gray color, like a luxurious cloak over the white fur on their bellies. The grey fur on their arms and legs fades into black on their hands and feet, like matching shoes and gloves. To complete their perfectly accessorized look, the pointed tufts of fur around their neck create a white collar separating their gray cloak from the gray of their head.
Diet
Like other langurs, the Hose’s langur is primarily folivorous, meaning their favorite thing to snack on is leaves. They mostly eat young leaves that are low in tannins making them easier to digest. These leaves are also more available across seasons. To digest a high cellulose food like leaves, langurs have long, multi-chambered stomachs similar to those of ruminants like cows. This gives langurs a pot-belly appearance, giving their digestive tract plenty of surface area to absorb as many nutrients as possible from their food. Also, from time to time, they enjoy fruits (mostly immature ones that, like leaves, are easier to find across seasons) and their seeds, flowers, and even bird eggs and nestlings for extra protein.
Hose’s langurs have been observed eating mud near mineral springs which, over time, form into hard concentrations of minerals (primarily calcium phosphate) in their stomachs called bezoar stones that are thought, in some cultures, to provide medicinal benefits to humans.
Behavior and Lifestyle
Hose’s langurs are diurnal, meaning they are active during daylight and sleep during the night. They are arboreal, spending most of their time high in the trees, climbing from branch to branch. While many primate species are arboreal, they differ in the amount of time spent in the trees and which level(s) of the canopy they tend to spend time in. For Hose’s langur, they like to spend most of their time in the trees, typically in the middle of the forest canopy around 65.62 feet (20 m) from the ground. The most common reason for their rare expeditions to the ground is to drink from sungans (or salt springs). This descending excursion is often prompted after a few days pass without rain.
While not well studied, researchers have noted some aspects of the daily life of a Hose’s langur. They live in groups with an average of six individuals but have been recorded in groups of up to 11 individuals. The group is led by a single adult male, with the rest of the group members being females and young. They have an average home range of 0.14 square miles (35 ha), of which they’ll typically travel 0.46 miles (740 m) in a day.
The Hose’s langur likely follows similar social habits of other langur species which, although they live in groups, are not very social. Grooming occurs infrequently among group members and, in some species, only among females. Males tend to be too busy guarding their group from other males to participate in social interactions.
They are sympatric (occur in the same geographic area) with maroon langurs, cross-marked langurs, and white-fronted langurs.
Not much is known about how the Hose’s langur communicates, although researchers have noted that compared to other surilis, Hose’s langurs do alarm-call as often when predators (including humans) are near and prefer to discreetly hide or flee the area. Males will use a special vocalization to warn other males to keep their group out of their territory. Both males and females will emit a variety of grunts to warn the group of potential threats. Females will chirp when near or in contact with other individuals, which is thought to be an affiliative sound, relating to social bonds.
Currently, not a lot is known about any species-specific characteristics of reproductive behavior in the Hose’s langur. We can expect that, like most langurs, females are responsible for initiating sexual encounters, typically by approaching the male and crouching to display her hindquarters to him. Also based on other langurs, we can assume that their gestation lasts about 6-7 months. Infants are usually weaned within their first year and are very often handled by other females in the group. Known as allomothering, having other females in the group help take care of infants allows mom to take a break, and can also give young females a chance to practice carrying a baby.
Like many aspects of the Hose’s langur’s life, there hasn’t been much research into their ecological role. Because they do eat some fruit and seeds, we can assume that they act as seed dispersers like many other primate species do. While a common ecological role among primates, seed dispersal is incredibly important in maintaining the biodiversity of the forests that these primates and many other animals call home.
Some scientists have also noted that leaf-eating monkeys like langurs may also act as ecosystem engineers, a term that biologists use to refer to any animal that modifies the structure of their environment (such as beavers). It’s thought that perhaps while munching on leaves, langurs open up patches for sunlight to penetrate lower parts of the forest canopy and prevent taller trees from fully blocking smaller ones.
The Hose’s langur is classified as Vulnerable by the International Union for Conservation of Nature (IUCN, 2015), appearing on the IUCN Red List of Threatened Species. In the early 2000s two studies on the population density of Hose’s langur found that, in the seven years between the studies, the population had decreased by 50-80%.
Hunting is also a major threat for the species, which is often targeted for bushmeat and for bezoar stones which are sold for use in traditional medicines, or turned into jewelry and other decorative pieces. While other ruminants or ruminant-like animals are also hunted for bezoar stones, including Javan rhinos, the ones from primates are the most expensive, making monkeys a valuable target for poachers. Hunters know to wait near sungans (salt springs) after rainless periods for the langurs to descend. Typically, it’s older sickly langurs that have bezoar stones, making them easier targets, although some hunters (typically those that don’t live in the area) will poison the sungans and kill hundreds of langurs.
As of 2010, 50% of Hose’s langurs’ habitat had been estimated to be lost due to human settlements, and wood pulp and oil palm plantations. It is estimated that about 19,305 square miles (50,000 ha) of forests remain. Being forced into closer proximity to humans increases Hose’s langur’s risk of being hunted and retaliated against for crop raiding, making this the greatest threat the species faces.
Hose’s langurs are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
Currently, there are few initiatives to protect the Hose’s langur. Although legally protected in Indonesia, their protection is not well enforced. They are also wrongly identified as Presbytis aygula which is the now outdated scientific name of the Javan surili, which Hose’s langur had formerly been lumped in with. This misnaming makes it easier for offenders who have harmed the species to evade prosecution.
- https://cites.org/eng/app/appendices.php
- https://www.iucnredlist.org/species/175648870/195370322
- https://wwf.panda.org/discover/knowledge_hub/where_we_work/borneo_forests/about_borneo_forests/ecosystems/lowland_dipterocarp/
- Barroso, M. D. S. (2013). Bezoar stones, magic, science and art. Geological Society, London, Special Publications, 375(1), 193-207.
- Nijman, V. (2010). Ecology and conservation of the Hose’s langur group (Colobinae: Presbytis hosei, P. canicrus, P. sabana): a review. Indonesian primates, 269-284.
- Nijman, V., & Nekaris, K. A. I. (2013). Loud calls, startle behaviour, social organisation and predator avoidance in arboreal langurs (Cercopithecidae: Presbytis). Folia Primatologica, 83(3-6), 274-287.
- Kirkpatrik, R. C. (2011). The Asian Colobines Diversity Among Leaf-Eating Monkeys. In Primates in Perspective (second, pp. 189–202). Oxford University.
- Bauchop, T., & Martucci, R. W. (1968). Ruminant-like digestion of the langur monkey. Science, 161(3842), 698-700.
- Chapman, C. A., Bonnell, T. R., Gogarten, J. F., Lambert, J. E., Omeja, P. A., Twinomugisha, D., … & Rothman, J. M. (2013). Are primates ecosystem engineers?. International Journal of Primatology, 34, 1-14.
- [Art Mitchell]. [Presbytis, hosei]. © All the World’s Primates. N Rowe, M Myers, eds. (alltheworldsprimates.org) Downloaded 2/21/2025
Written by Lina Rademacher, February 2025