GEE'S GOLDEN LANGUR

Trachypithecus geei

Geographic Distribution and Habitat

Gee’s golden langurs, also known as golden leaf monkeys, or more simply as golden langurs, live in northeastern India and southern Bhutan. They are confined to this geographic region by the Manas and Sankosh rivers to the east and west, the Brahmaputra river in the south, and the Black Mountains to the north. Here, altitudes vary greatly; golden langurs may live anywhere between sea level and 9800 feet (3000 m) above sea level. This is a considerable range for primates.

This species thrives best high up in the canopies of subtropical and temperate broadleaf forests. However, golden langurs also make do in lowland evergreen, semi-evergreen, riparian moist deciduous forests, subalpine forests, and savannas, as well as secondary or degraded forests. A single, isolated population of golden langurs even lives in the Abhaya Rubber Plantation, in the Kokrajhar district in Assam, India; and has been the subject of a number of eye-opening studies into this shy, and often elusive, species.

The total amount of habitat considered suitable for golden langurs, in both India and Bhutan, has dropped significantly in the last several decades and now hangs at less than 193 square miles (500 km2). 

TAXONOMIC NOTES

Over the years, the Gee’s golden langur has shuffled through a number of scientific names. At first categorized under the genus, Presbytis, and then Semnopithecus, it was finally placed in Trachypithecus, a genus describing the lutungs, langurs, and leaf monkeys found across Southeast Asia.

A 2003 study described a new subspecies of golden langur in northern Bhutan, known scientifically as Trachypithecus geei bhutanensis. The study did not follow IUCN protocols for identifying a new subspecies, thus the proposed subspecies has not been recognized by the IUCN. Since then, this population of langurs in question has been found to be a hybrid between golden langurs (T. geei) and capped langurs (T. pileatus).

Gee's golden langur range, IUN 2020. Zoomed in.
Gee's golden langur range zoomed out. Range circled in red.

Size, Weight, and Lifespan

Golden langurs are relatively small primates, weighing between 19 to 26 pounds (9 to 12 kg). Males, measuring an average of 37 inches (950 mm) from head to butt, tend to be slightly larger than females at 35 inches (890 mm).

Tail length marks a considerable difference between the sexes. The average male golden langur sports a tail longer than his body, at 38 inches (975 mm) long, while an average female golden langur has a tail measuring only 34 inches (866 mm).

Male golden langurs also tend to have larger canine teeth, on average 0.7 inches (18 mm) in length versus a female’s half-inch (14.5 mm) fangs. For primates, the size of canine teeth can often predict the hierarchical relationships between the sexes.

A shy and elusive species that bolt at the sight of humans, researchers have a hard time tracking golden langurs over a long period of time. Therefore, it has been difficult to gather data on how long they live in the wild.

What Does It Mean?

Genetic bottleneck:
When a species’ population is reduced in size (i.e. by a cataclysmic event, habitat fragmentation, etc.) limiting the genetic diversity of the species.

Inbreeding:

The breeding of closely related individuals, especially over many generations.

Sympatric: 
Occurring or living in the same area; overlapping in distribution.   

Visit the Glossary for more definitions

Appearance

Golden langurs are easy to identify by their golden fur. Individual coats can range from dark gold to a creamy, buffy color. Their thick, wiry hair gives them a magical, almost other-worldly, countenance; like something out of a Jim Henson* film. Tufts of golden-and-black woven hair erupt from their faces like an exuberant wreath of solar flares, hiding their naked black ears.

Their lush golden coats of fur can’t quite hide golden langurs’ lanky limbs and slender frames. Long black fingers and toes extend visibly from their furry hands and feet. A signature tassel marks the ends of their majestically long tails.

Golden langur’s coats change color with the seasons, darkening to a golden chestnut hue in the winter and lightening to a creamy tone in the summer. Populations in the south are also found to sport more uniform coats than in the north where there is greater variety.

Like other leaf-eating monkeys, the color of young golden langurs differs from that of adults. Like a marshmallow held over a flame, newborns start out with completely white fur that gradually goldens as they mature. 

*(Jim Henson was the creator of The Muppets and Fraggle Rock.)

Diet

Golden langurs are primarily folivores, meaning they eat leaves. Though they chow down on a large variety at all stages of growth, softer, young leaves are clearly preferred over chewier, mature ones. 

Fruit, both ripe and unripe, are another staple in this species’ diet. Certain seasonal fruits are one of the few items otherwise peaceful golden langurs regularly fight over. Certain flowers, especially the yellow buds and blossoms of the balu tree, are beloved as well. For some groups, leguminous shrubs provide tasty morsels worth the trip to the understory.

Golden langurs have also been observed eating lichens, algae, insect galls, bark, twigs, wild potatoes, insects (like termites), insect larvae, and snails. Some groups are known to raid local farms, attracted by their delicious cardamom, tapioca, and guava crops.

Golden langurs have specialized stomachs composed of multiple chambers. Each chamber helps to break down the tough fibers found in the leaves, bark, and whatever cellulose-rich plant material they may ingest. Though it makes digestion a long, drawn-out process, this important adaptation ensures the langurs obtain the maximum nutrition from every single meal.

Behavior and Lifestyle

Golden langurs are arboreal, living high in the canopy where they clamber up trees on all fours and make daring leaps between branches in order to get around. This lifestyle, plus their tendency to be quite secretive, makes them a difficult species to study in the wild. Groups often vacate an area as soon as humans show up. When a group chooses to stay put, the langurs’ obvious awareness of the researchers makes it impossible to judge how genuine and “natural” their behaviors really are.

These langurs seldom leave the safety of the canopy. They do so only when a large gap in the trees makes it completely necessary or if something particularly alluring (like natural salt licks) draws them down. Summer is the season when golden langurs visit the forest floor most often, doing so in order to hydrate themselves at watering holes on the forest floor. During wetter seasons, langurs are able to get all the water they need from the rain and moisture that condenses on the foliage of the canopy.

Golden langurs are not especially territorial monkeys. At times, groups may even mingle and mix. A group is most likely to defend its range when drought or another natural disaster has greatly reduced the amount of resources in the region. Defense, however, usually just means intimidation. Physical violence is practically unheard of in this species.

Fun Facts

Golden langurs choose to roost in trees with less foliage in the winter than in the summer, letting them soak up the heat of the sun.

Golden langurs are more active during their rest periods on cloudy days than on sunny ones.

Daily Life and Group Dynamics

Forest type and the abundance of food are two factors theorized to affect the sorts of groups golden langurs form. The largest groups observed (sometimes as large as 50 members) all live in places where habitats have become severely degraded. These groups may have a significantly higher population density but their birth rates are also much lower. In more natural settings, golden langurs live in groups of 3 to 15 members.

Golden langur form male-dominated, multi-female groups. Most groups have a single adult male, but larger ones may have up to two males. In either case, the dominant male controls his group’s movements. 

Golden langurs are not necessarily territorial and inter-group conflict is rare. Different groups only show aggression when highly valued resources may be threatened. Otherwise, langur groups may even mingle and mix. They even generally live in peace with other sympatric species of monkeys, like rhesus monkeys and Phayre’s leaf monkeys. In Bhutan, golden langurs are even speculated to mate with their capped langur cousins.

A group of golden langurs wakes early in the morning and begins feeding straight away. They chow down on leaves and whatever else they find in their vicinity. Stuffed, it’s time to take a rest. Though their stomachs are specially adapted to ensure they get the most possible nutrients out of their high-fiber diets, it doesn’t make this process less arduous. Plopping down on a branch high in the canopy, safe from predators, is basically necessary. Rest takes up almost half of the average langur’s waking hours.

Long periods of rest do not necessarily mean sleep, however. A monkey chilling on a branch is often being groomed by another. After a while, the two switch roles. Juveniles use this time to play, wrestling and chasing each other, climbing, running, and jumping. Sometimes the younger langurs even join in. Their mothers appear to doze off, but they always keep one eye open, watching out for the safety of their young. Meanwhile, the dominant males keep an eye out for predators, always ready to sound the alarm.

By the afternoon, the group has digested their breakfasts enough to travel to another spot, led to a fruit tree by the dominant male. They all stuff themselves full once more before resting again. As the light disappears from the sky, the langurs may have one last bedtime snack before settling down for the night in the same trees in which they’ve just foraged.

Communication

Since they are so secretive, the ways by which golden langurs communicate are not well documented at this time. But all langurs are social monkeys. They use vocalizations, gestures, body language, and facial expressions to communicate with each other.

Male golden langurs keep a close tab on threats, sounding the alarm whenever he detects one. To do this, he makes a high-pitched call. He always lets his group run or take cover before following them. Females and juveniles make their own type of alarm call, a high-pitched “eeeeh.” Usually, this means they have become separated from the group.

Golden langurs know there is safety in numbers. When a member becomes separated from the group, they are in great danger. Contact calls help golden langur groups stay together, especially during the chaos of travel. Their contact calls need to be loud enough that nearby group members can hear them but not so loud that they draw unwanted attention from predators who easily use the noise to track the group through the dense foliage. Thus, these calls are short growls that only nearby langurs are able to make out clearly. Each langur makes this call frequently as they travel, trying to prevent anyone from getting lost or separated.

Though not often territorial, male golden langurs do get into occasional squabbles. Usually these are inter-group, not intra-group, conflicts. When the dominant males of two groups get into a disagreement, they dart back and forth along a branch while making loud grunts, attempting to intimidate the other. If their nemesis doesn’t back down, they open their mouths wide, showing off their canines, while emitting a quick series of loud and sharp notes. These signals may appear aggressive, but they are actually used to prevent violence. Through these displays, disagreements rarely become physical.

Researchers have noted that males make a low growl while eating, but what it might signal or communicate is not entirely clear. Indeed, the nuances of golden langur communication wait to be revealed through further observation.

Reproduction and Family

Not much research has been done on the reproductive behaviors of golden langurs. But some researchers surmise that they are probably not unlike those of gray langurs.

It is known that golden langurs mate year-round, but most mating takes place in the drier seasons between the months of May and November. Females remain pregnant for an average of 180 days before giving birth, usually between the wetter months of December and June when food is most abundant.

A newborn golden langur isn’t golden at all, but completely white. This marks him as someone the adults should look out for and protect. During his first year, he does hardly anything but suckle and sleep. Gradually, he begins to practice gross-motor movements like pushing and pulling. By around 2 years (14 months), he has been weaned and—though he can’t go very far—begins to leave the warm comfort of his mother’s fur. By four years of age (42 months), he reaches juvenile status. By now his coat has started to darken. Though he still needs practice, he now has the motor control to climb and leap all on his own.

A year later, his fur has goldened completely. Yet he’s still not quite ready to strike out on his own. Sometime in the next few months, however, he fully matures and leaves his natal group. For now, he joins a band of other young adult males who watch each others’ backs while they wait to join or create another group. It is not yet clear how or when new golden langur groups form.

Females develop along a similar timeline as males, but they do not leave their natal groups when they reach maturity. The age at which an average female gives birth for the first time is around 4.5 years (59 months). Because child-rearing is so time-consuming and energy-draining, she puts off having another until her latest offspring is already weaned.

Raising the young is the responsibility of the females. While mothers nurse their own offspring, every female in the group helps every other. They take turns babysitting and grooming each other’s offspring, a phenomenon commonly found in many folivorous monkeys called allo-mothering.

Males are almost completely hands-off with their offspring. As vigilant protectors of their group, however, they do play an important role in ensuring their safety. Infanticide has never been reported among golden langurs, even when dominant males have been supplanted.

Researchers have noticed a surprising trend in golden langur society in which mating pairs are approached by other group members. Sometimes other females might simply gather to watch. Other times, a single female might show her behind, trying to persuade the male to mate with her instead. Other times, females may actively harass the couple and keep them from being able to finish.

Ecological Role

Golden langurs help disperse the seeds from the fruit they eat. As the langurs travel to find food, the seeds they’ve recently ingested travel through their digestive tracts, falling to the forest floor in their feces far from where they originated. This process is critical to healthy forest development and sustainability.

Conservation Status and Threats

The Gee’s golden langur is classified as Endangered by the International Union for Conservation of Nature (IUCN, 2015), appearing on the IUCN Red List of Threatened Species. Currently, this species’ population is estimated at only 6,000 to 6,500 individuals. The rate of their decline is higher than 60% in India and likely even higher in Bhutan. Unfortunately, this downward spiral is expected to continue for at least the next two decades. 

Habitat loss and fragmentation spurred by human activities in the region are by far the greatest threat to golden langurs’ existence. At least 50% of their habitat in India disappeared in a ten-year period between 1988 and 1998. Since that time, little has been done to curb the tide. In fact, things have only gotten worse. Though commercial logging has been banned in reserves, illegal logging practices have continued without penalty. Smaller logging interests and wood collection for fuel, both firewood, and charcoal compound this problem further. 

Throughout golden langurs’ geographic range, forests are continually converted to land for farming and pasture for grazing. Villages, towns, and other human settlements pop up wherever valuable resources create financial interests. Once established, they start to sprawl, causing golden langur habitat to shrink. Due to these long-held trends, golden langurs now only exist in a handful of isolated forest fragments.

Modern human civilization requires a great deal to sustain itself. The necessary infrastructure projects further destroy and degrade the forests, creating a host of other problems for golden langurs. Roads, highways, and rail systems further fragment their already severely fragmented habitats. Even the smallest gap in the trees can be insurmountable for arboreal creatures like golden langurs. When a gap proves too big, langurs venture to the ground in order to press forward. If the gap is created by a road, the langurs are then vulnerable to whatever traffic happens by.

As habitats become more fragmented, populations become hopelessly separated from each other and gene flow slows to a halt. When this happens, inbreeding is likely to increase and genetic bottlenecks form. As this occurs, after only a few generations golden langur offspring may become more vulnerable to diseases, parasites, and birth defects that affect their overall viability. Extinction becomes imminent when individuals no longer live long enough to be able to pass on their genes.

The construction of dams not only contributes to habitat fragmentation but can affect whole ecosystems downstream that rely on steady water flow to sustain themselves. Electric power lines add another hazard for langurs, especially young langurs. Studies find that, along with dog attacks, high-voltage electric shock is the number one cause of infant mortality for golden langurs. Poisoning by insecticides used on crops is another contender.

Political and social unrest in the regions where they live complicates the golden langurs’ situation even further. Driven by their own biological needs for space and resources, and not having anywhere else to go, displaced peoples continue to settle in the langurs’ last remaining habitats. These tensions make taking action to enforce legal protections of golden langurs that much more complicated. As such, they are frequently ignored.

Golden langurs are a secretive species who take flight at the sound of loud, unfamiliar noises. Human settlements create a great deal of noise pollution that can spook and stress langurs, interrupting their daily routines. This may not seem like a big deal to humans already used to sacrificing their peace and quiet for the comforts of civilization, but for vulnerable langurs who spend a significant amount of their time at rest, it most definitely is! Quarrying for stone and military artillery practice are two other human activities that cause a great deal of unprecedented noise pollution and to which golden langurs are regularly subjected in this region.

Conservation Efforts

The Gee’s golden langur is listed in Appendix I 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. It is a Schedule I species in the Wildlife Protection Act (1972).

Golden langurs only live in a single protected habitat in India, known as the Chakrashila Wildlife Sanctuary. Though sightings have been reported in the Ripu, Chirrang, and Manas forest reserves, they are not confirmed. Regardless, these reserves are generally considered to be poorly managed. In Bhutan, golden langurs live in the Jigme Singye Wangchuck, the Royal Manas, and Thrumshingla national parks, as well as the Pipsu Wildlife Sanctuary.

In order to bring golden langurs back from the brink of extinction, much still needs to be done. Enforcing protections that already exist is barely a start. Long-term studies that assess the full impact of habitat loss and fragmentation on this species are desperately needed. Similar studies into golden langur behavior and ecology are necessary to help guide conservationists toward implementing a meaningful conservation plan for this species. The first step towards initiating such research is by upgrading their protection and status.

In the meantime, projects to regenerate forests could begin to quell the tide surging against golden langurs. Creating eco-corridors would reconnect long separated langur groups, allowing genes to flow more freely again. An initiative to better insulate power and divert power lines would prevent more golden langurs, especially young langurs, from dying of electrocution. Public awareness campaigns meant to educate local people about the importance of golden langur conservation would encourage their participation, even if that only means restraining their dogs to prevent them from mauling more langurs. All of these projects and more would create new and unexpected opportunities for locals, like jobs, helping to bring more prosperity to the region.

In 2011, the Central Zoo Authority of India initiated a conservation breeding program for Gee’s golden langurs at Assam State Zoo at Guwahati. The golden langurs involved are not for the viewing public. Unfortunately, there has been no news of the program’s success.

References:
  • https://www.alltheworldsprimates.org
  • https://www.iucnredlist.org/species/22037/17960997
  • https://cza.nic.in/uploads/documents/studbooks/english/nsGolden%20Langur.pdf
  • https://www.researchgate.net/publication/352776123_Persistence_of_Trachypithecus_geei_Mammalia_Primates_Cercopithecidae_in_a_rubber_plantation_in_Assam_India
  • https://www.researchgate.net/publication/341621880_Influence_of_habitat_conditions_on_group_size_social_organization_and_birth_pattern_of_golden_langur_Trachypithecus_geei
  • https://www.researchgate.net/publication/307010500_Genetic_Diversity_and_Structure_among_Isolated_Populations_of_the_Endangered_Gees_Golden_Langur_in_Assam_India
  •  https://www.thehindu.com/sci-tech/energy-and-environment/assam-zoo-plans-to-breed-highly-endangered-golden-langur/article2120048.ece
  • https://animaldiversity.org/accounts/Trachypithecus_geei/
  • https://animalia.bio/gees-golden-langur

Written by Zachary Lussier, November 2022