Bornean Banded Langur, Presbytis chrysomelas
BORNEAN BANDED LANGUR
Presbytis chrysomelas
Geographic Distribution and Habitat
The Bornean banded langur (Presbytis chrysomelas), also called the Sarawak surili or cross-marked langur, is native to the island of Borneo, which is split between Brunei, Indonesia, and Malaysia. They live in swamps, lowland forests, and among mangroves.
Borneo is a hotspot for primates, home to a full 17 species. Langurs are the most widely distributed primate group in Borneo. However, Bornean banded langurs have the most restricted distribution of any langur on the island, in large part because their range has decreased dramatically in recent years. They are believed to occupy just 5% of their historic range. There are five documented sites where Bornean banded langurs are known to live, all within the Malaysian state of Sarawak. These sites are Samunsam Wildlife Sanctuary, Tanjung Datu National Park, Gunung Pueh National Park, Similajau National Park, and Maludam National Park, respectively. In early 2024, reports came in of a sixth site that may house permanent populations of the langurs: Jemoreng Protected Forest.
While langurs as a whole are well-studied, those studies tend to focus on more widespread members, such as Raffles’ banded langur (P. femoralis). Bornean banded langurs are difficult to study not only because of their reclusive lifestyle, but also because of the habitats they live in — deep peat swamps inhabited by crocodiles and venomous snakes may be cozy for the langurs, but not so much for human researchers. These environments also tend to be very sensitive to human disturbance, making scientific documentation even more difficult. As a result, there is much that we do not know about this highly endangered species. Much of the information in this profile has therefore been gleaned from what we know of other related species.
Bornean banded langurs were formerly considered subspecies of Raffles’ banded langur (P. femoralis) and the black-crested Sumatran langur (P. melalophos) before being recognized as their own species. There exist two recognized subspecies of Bornean banded langurs: the black morph, P. chrysomelas chrysomelas, and the red morph, P. chrysomelas cruciger, which is also known as the tricolor langur. There is another isolated population of Bornean banded langurs that may represent a third subspecies, although research into this population is currently lacking.
Size, Weight, and Lifespan
Bornean banded langurs are medium-sized primates. Based on their close relative, the Raffles’ banded langur, they likely measure 17 to 24 inches (43-61 cm) in length from their head to the base of their tail. Their tail is about 24 to 33 inches (61-84 cm) in length, and they weigh approximately 13 to 18 lbs (5.9 to 8.2 kg). Most likely, they live to the age of about 20 or 30 in the wild.
Appearance
The two subspecies of Bornean banded langurs are very easy to tell apart as adults. The subspecies referred to as the Bornean banded langur, P. c. chrysomelas, displays the black morph and is jet black over most of its body. Its underside may be a pale white up the chin and wrists and down to the bottom of the tail. The subspecies called the tricolor langur, P. c. cruciger, displays the red morph.
They are red-orange over much of their body but have black arms and hands and a black back. Both morphs have bald faces, usually with gray skin, and are rather gaunt. Their cheekbones are prominent, giving their face a rather sunken appearance. Their eyes are very large and round, which may help them to take in more light in their shady forest habitats. Juveniles of both subspecies may be gray, reddish, or pale white, with black backs and arms and a pale belly.
Diet
Somewhere between 25-65% of their diet consists of fruits and seeds, likely varying depending on the time of year. Leaves also make up a significant portion of their diet. Some of their favorite fruits include those from the Resak Lari tree, the Mengkudu Besar tree, which is in the coffee family, and the kerueh tree.
Behavior and Lifestyle
Bornean banded langurs are diurnal, meaning they are awake during the day, and arboreal, meaning that they spend most of their lives in the trees, though they have been sighted on the ground. One study of the black morph subspecies showed that the monkeys have relatively short movements, spanning just 105 to 177 feet (32 to 54 m) per day, suggesting that they did not travel much during this study. However, as this is based only on one study, this could vary by time of year or between populations. They wake at dawn, usually around 6 am depending on the time of year. Several small studies have indicated that Bornean banded langurs tend to rest more often in the afternoon, which they usually do while sitting in a hunched position on a branch. There are three peaks in their activity each day: 8 am-9 am, 3 pm-4 pm, and 5 pm-6 pm. In the evening, they find a sleeping tree in which to spend the night.
Bornean banded langurs are known locally by several different names. They are known as penatat or penyatat by the Bidayuh community, lutung by Malays, bijit by the Iban people, and berangad by the Kenyah people.
Bornean banded langurs usually live in small groups of three to seven individuals, though groups of up to 20 individuals have been observed. The group is usually composed of an adult male, one to three adult females, and their offspring. One study that took place over two months collected behavior data on three Bornean banded langur groups. It found that they spend about a third of their time (31%) resting, slightly less time (29%) moving, 26% of their time feeding, and 14% of their time vocalizing. They spend significantly more time feeding and vocalizing than other closely related species. For comparison, Raffles’ banded langur (P. femoralis) spends just 2-4% of their time vocalizing. Another study focused on the red-morph subspecies, the three-color langur, found that their social activity was about half agonistic behaviors, which are those that are associated with conflict. Vocalization comprised about 40% of their social behavior and playing comprised about 10%.
Vocalizations include a chuckle-like “tat tat”, then a pause, followed by a faster “tat tat tat”. Their vocalizations are unique to them, and an important tool in distinguishing them from other closely related species. They spend a great deal of their time vocalizing. They usually start in the early morning, even before leaving their sleeping tree. This is thought to help coordinate with other group members. They also often vocalize while moving. Vocalizations help to keep the group together and cohesive and are an important tool to warn of predators.
Research into the reproductive lives of Bornean banded langurs is unfortunately sorely lacking. However, we can glean the basics from their close relatives. They are likely polygynous: this means that a single male mates with multiple females. Their gestation period, the length of time they’re pregnant, is likely about 200 days, or six and a half months, after which they give birth to a single baby. It is not known what roles each parent plays in rearing the baby, or if other adults in the group help to raise the offspring at all. Young reach sexual maturity at around 6 years of age, and females can keep reproducing into their late teens.
Bornean banded langurs live alongside several of the many primate species that call the island of Borneo home. These include long-tailed macaques (Macaca fascicularis), pig-tailed macaques (Macaca nemestrina), silver leaf monkeys (Trachypithecus cristatus), and Abbott gibbons (Hylobates abbotti), among others. Their predators are not documented but likely include some of Borneo’s carnivorous mammals, such as the endangered Sunda clouded leopard or the Borneo bay cat.
The International Union for Conservation of Nature lists the Bornean banded langur as Critically Endangered (IUCN, 2015) appearing on the IUCN’s Red List of Threatened Species. This is the last step before extinction in the wild. This assessment is based on an 80% loss in population over the last 30 years, or three generations. In just the last century, Bornean banded langurs have gone from a common primate to one of the rarest in the world. Previously widespread throughout their range, they now exist at just five sites, comprising only 5% of their historic range. The main cause of this staggering loss is habitat loss from palm oil plantations, which has not slowed down. Without immediate and effective conservation action, Bornean banded langurs will soon go extinct.
While most of their habitat has been lost to oil palm plantations, human development continues to cut into what little remains. In 2018, a new stretch of the Pan Borneo highway was carved through the Samunsan Wildlife Sanctuary, one of the few sites where Bornean banded langurs are known to live. It significantly disturbed the habitat there and also disturbed the important natural connection between Samunsan and Tanjung Datu National Park. Where roads are built, more development follows. A new resort has since been proposed along the highway, which would be built over more habitat where the langurs have been spotted.
Bornean banded 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. While there exist some protected areas throughout the langurs’ range, such as Maludam National Park and the Samunsam Wildlife Sanctuary, they are believed to house only about 200-500 individuals.
More research focusing on Bornean banded langurs is desperately needed. A top research priority is learning more about their population size and distribution. Sadly, at the rate that their habitat range is shrinking, observed populations of Bornean banded langurs in one area may no longer live there. We need up-to-date data on distribution to be able to prioritize areas for conservation.
- Ampeng, A., et al. 2023. First recorded sighting of the Critically Endangered Tricolour Langur, Presbytis chrysomelas cruciger (Thomas, 1892) (Primates, Cercopithecidae), in Jemoreng Protected Forest, Sarawak, Malaysia. Check List 20(20): 518-523.
- Faishal M., Muhammad, & Santoso, N. 2020. Habitat Characteristics and Activity Patterns of Cross-marked Langur (Presbytis chrysomelas cruciger) in Danau Sentarum National Park. Jurnal Penelitian Hutan dan Konservasi Alam. 17:155-172.
- Harley, D. 1990. Aging and reproductive performance in langur monkeys (Presbytis entellus). Am J Phys Anthropol. 83(2):253-61.
- Noor-Faezah, M., et al. 2023. A brief review of Bornean banded langur Presbytis chrysomelas (Müller, 1838) of Sarawak. Journal of Wildlife Biodiversity 7(4):265-282.
- Nur-Aizatul, T., et al. 2024. Preliminary assessment of group composition and activity pattern of the critically endangered Bornean Banded Langur Presbytis chrysomelas chrysomelas in Tanjung Datu National Park. Biodiversity Data Journal 12.
- Santoso, N., Sutopo, Meo, L. E., Fauziah, N. N., & Diva, A. M. (2023). Preliminary study: Feeding ecology and daily activity of three colored langur (Presbytis chrysomelas ssp cruciger Thomas, 1892) in Danau Sentarum National Park. Biotropia 30(2), 206–219.
- https://www.iucnredlist.org/species/39803/17955321
- https://wildlife-biodiversity.com/index.php/jwb/article/view/375
- https://borneoadventure.com/blog/2018/09/sarawak-langur/
- https://animalia.bio/banded-surili?custom_list=128
- https://primate.wisc.edu/primate-info-net/pin-factsheets/pin-factsheet-gray-langur/
Written by K. Clare Quinlan, September 2024