Sabah Grizzled Langur, Presbytis sabana
SABAH GRIZZLED LANGUR
Presbytis sabana
Geographic Distribution and Habitat
The Sabah grizzled langur, also known as the crested grizzled langur, or the Saban gray langur, is found on the island of Borneo, in the Malaysian province of Sabah. Within their range, they are found in evergreen, lowland, riparian (on a riverbank or stream), montane (mountainous) forests, and tree plantations.
The Sabah grizzled langur was once considered a subspecies of the Hose’s langur (P. hosei).
Size, Weight, and Lifespan
The Sabah grizzled langur has a head-body length ranging between 19-22 inches (48-56 cm), and a looooong, nonprehensile tail measuring 25-33 inches (64-84 cm). Along with being slightly longer than females, male weight ranges between 13-15 pounds (6-7 kg), while female weight ranges between 12-13 pounds (5.5-6 kg). These differences in size and weight are examples of sexual dimorphism, which are noticeable physical differences between genders aside from genitalia.
The exact lifespan of the Sabah grizzled langur is not known, but langurs typically live to about 25 years of age.
Appearance
An endearing and captivating monkey, the Sabah grizzled langur is primarily gray with a grizzled pattern, and a pointed crown on the top of the head, giving a distinctive appearance. The hands and feet are black, while the underparts (inner arms, legs, and chin) and belly display contrast with a white coloration. Their spade-shaped faces are typically reddish-pale, with dark rings around their expressive eyes.
Infants, by comparison, are born with lighter fur, which darkens as they mature.
Diet
The Sabah grizzled langur mainly consumes young leaves, unripe fruit, seeds, and flowers. They also have been documented eating buds, bark, insects, bird eggs, nestlings, and mud rich in minerals. To extract as many nutrients as possible from the tough, leafy material in their diet, they have evolved specialized stomachs perfect for fermenting the rough greens.
Their diets vary with the extent of habitat degradation (logging) in different forests, as well as different times of the year. According to a few resources, on average, young leaves comprise 42-45% of the diet, fruits 3-25%, seeds 17-21%, mature leaves 1-5%, and flowers 3% or less. More leaves are eaten in unlogged forests (78% of the diet vs. 60% in logged forests), and more fruits and seeds are eaten in logged forests (19% fruits and 21% seeds vs. 3% fruits and 17% seeds in unlogged forests).
Behavior and Lifestyle
The Sabah grizzled langur is diurnal, being most active during the day, and arboreal, preferring to spend those days in the trees. During the night, they sleep usually in the middle and upper branches of emergent trees topping the forest canopy.
According to one resource, the following activity budget has been observed: 45.1-49.5% of their time is spent resting, travel takes up 30.2-32.1% of their time, 13.9-17.5% of the day is spent foraging, 4.7-6% is dedicated to social activity, while the remaining 0.5-0.6% is dedicated to simply-put, “other”.
Almost as varied as their diet are their methods of locomotion. According to one resource, most (58.8%) of their moving around is done quadrupedally, or on all fours, 22.3% of their locomotion is climbing, 10.2% leaping, 6.5% vertical clinging and leaping, and 0.8% suspended amongst the branches.
While there is no specific documentation regarding the non-human predators of the Sabah grizzled langur, if we look at another species that share their geographic range, the silvery lutung (Trachypithecus cristatus), their predators include leopards and snakes. They avoid predators by emitting staccato grunts as alarm calls. What is done afterward has not been documented specifically with this species, but a neighbor of theirs, the maroon leaf monkey (P. rubicunda), has been known to “predator mob”. In this scenario, the monkeys will all emit loud calls and cause an uproar to overwhelm and chase the predator away. Don’t mess with the mob!
Magic stones?: Admittedly, not a fun fact, the Sabah grizzled langur is hunted by humans in part for “bezoar” stones found in the gastrointestinal (GI) tract. While this will be explained further in “Conservation Status and Threats”, the word “bezoar” comes from the Persian “pād-zahr”, which literally means “antidote”.
Born to be wild: The Sabah grizzled langur has not been reported to be in captivity anywhere.
A group of Sabah grizzled langurs is composed of a single dominant male, two to six adult females, and their young, totaling up to 14 individuals. Home ranges vary between 86.5-309 acres (35-125 ha), and daily travel distances are usually around 0.43-0.50 miles (700-800 m). With regard to who stays and who leaves the natal group, females are known to leave upon reaching sexual maturity to search for another group, while newly mature males will lead a solitary life until perhaps forming a group of their own.
With regard to associating with other primates, the Sabah grizzled langur has been recorded in close proximity with, and even occasionally mixing in groups of maroon leaf monkeys, as well as their formerly assigned subspecies categorization, the Hose’s langur, while traveling and feeding.
The Sabah grizzled langur exhibits strong familial bonds, and to reinforce social structure, engages in mutual grooming. Communication is otherwise facilitated through a combination of vocalizations, facial expressions, and body postures.
Speaking of vocalizations, the Sabah grizzled langur has quite a variety of them:
A gargling growl is a loud, long call emitted by the adult male of the group to display his strength against other males, promote group cohesion in the middle of the day, and maintain territorial boundaries among groups.
A staccato grunt is an alarm call emitted by the adult male.
A single grunt is emitted by an adult of either gender in cases of “mild alarm” or “concern”.
High-pitched rattled chucks are alarm calls emitted by adult females.
Quiet chirrups are potential contact calls emitted by adult females and sub-adults.
Squeals are emitted by juveniles and infants and are used for play, aggression, and to exclaim hunger.
The Sabah grizzled langur is polygynous, meaning one male has exclusive breeding rights to all of the females in the group. There is no set breeding season, and after a gestation (pregnancy) period of 5-6 months, females give birth to a single offspring from July to October. Parental involvement by gender regarding the Sabah grizzled langur is unknown, but langurs as a whole have been known to participate in alloparenting, in which all of the females in a group will help to raise each other’s offspring.
Infants are weaned from Mom’s milk at around 11 months of age and are considered to be subadults at 21-36 months of age. Both genders reach sexual maturity, and thus, independence, at three years of age. Upon reaching independence, they will leave their natal group, and eventually, hopefully, start a group of their own.
As fruit-eaters, Sabah grizzled langurs aid in the regeneration of their forest habitats by dispersing seeds through their feces as they travel throughout their habitat. In addition, by feeding extensively on young leaves, they largely strip trees of these leaves. This stimulates the trees to recover by producing a new set of young leaves, thereby increasing their productivity and growth rate. They also play a role in pollination. Like bees and butterflies, they collect pollen from flowers when consuming them. They then deposit the pollen on each subsequent flower they visit, thereby pollinating the plants. In addition, they may serve as pest controllers, since a portion of their diet is made up of insects. Finally, as a prey species, they also play a role in feeding local predators within their range.
The International Union for Conservation of Nature lists the Sabah grizzled langur as Endangered (IUCN, 2015), appearing on the IUCN Red List of Threatened Species.
The Sabah grizzled langur is hunted by humans both for food as well as “bezoar” stones found in the GI tract, which are believed to have medical/therapeutic value. This hunting pressure is believed to be the principle cause of their declining population.
While the Sabah grizzled langur is rather adaptable and well tolerant of “light” logging, mass clearings and destruction of canopies within which they move and sleep are significant threats to their survival.
The Sabah grizzled langur is 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.
The Sabah grizzled langur is found in a number of protected areas, including the Danum Valley Conservation Area, Tabin Reserve, Sepilok Orang Utan Sanctuary, Lower Kinabatangan, and Maliau Basin Conservation Area in Sabah.
Conservation actions needed include additional land, water, site, and area protection and management, harvest management, as well as education, communication, and public awareness of the plight of the Sabah grizzled langur. Further monitoring of the langur’s population and habitat trends, alongside a species action or recovery plan, as well as an area-based management plan, would greatly contribute to the conservation cause. Additional research on the Sabah grizzled langur’s population size, distribution, and trends, life history and ecology, harvest, use, and livelihoods, and threats are all necessary should this endearing species of Borneo stand a chance against the looming threat of extinction.
- https://www.alltheworldsprimates.org/Members/Home/MasterPrimate.aspx?tid=1285
- https://www.bioexplorer.net/animals/mammals/monkeys/saban-grizzled-langur/
- https://www.columbuszoo.org/animals/silvered-leaf-langur
- https://en.wikipedia.org/wiki/Presbytis
- https://en.wikipedia.org/wiki/Sabah_grizzled_langur
- https://www.facebook.com/RBLWG/posts/primates-of-malaysia23-sabah-grizzled-langur-presbytis-sabanathe-sabah-grizzled-/2636261196646039/
- https://www.gbif.org/species/8022434
- https://www.iucnredlist.org/species/39810/17987041
- https://tb.plazi.org/GgServer/html/CE199B17FF98FF9EFA036F44FB54F7A6
- https://upcubewildlife.com/sabah-grizzled-langur-detailed-profile/
Written by Sienna Weinstein, November 2024