Trachypithecus popa

Geographic Distribution and Habitat

A Popa langur lives in the high evergreen forests of Myanmar, particularly the sacred pilgrimage site of Mount Popa (an extinct volcano), which gives the langur its common and scientific names. The main populations are found in Popa Mountain Park and Panlaung-Pyadalin Cave Wildlife Sanctuary. 

While they are mostly found in evergreen or mixed deciduous forests, some populations have been spotted living in bamboo forests, closer to more disturbed areas like plantations.


The Popa langur was discovered as a new species in 2020 in a lab and from skins maintained in a museum! For 100 years, museums had preserved skins of these primates and assumed any visual differences were because of natural variation within the same species. Langurs in this Myanmar region belong to a Trachypithecus obscura group and many of the species in the group are endangered. The main differences between the Trachypithecus in this region are not immediately visible. The low population numbers make it difficult to determine different species by only observing the primates in the wild. So researchers decided to genetically test the skins and they discovered significant differences between skins that were consistent with the visual differences. And thus a new species—the Popa langur—was described!

The Popa langur tends to be more gray than brown and their head has a more rectangular shape than their close relatives. The most consistent difference is that the Popa langurs have larger canine teeth than similar species.

Popa langur range, IUCN 2022

Size, Weight, and Lifespan

Popa langurs weigh between 15 and 17 pounds (7–8 kg). From the head to the base of their tail, they measure between 20–23 inches (50–60 cm) and have a distinctly long tail which is about 31 inches (80 cm) long. 

There is no documented lifespan for the Popa langur but other species within the genus are known to live for 20 years in the wild and up to 30 years in captivity. (Captive animals tend to live longer because of the lack of predators, though their quality of life is probably lacking).


These small monkeys are covered in soft fluffy gray fur and have the characteristic pointed cap of fur on their head, like most langurs. Their small heads are dominated by large eyes made bigger in appearance by thick white eye rings that appear painted on. They have small, elongated nostrils, and a wide mouth covered in white fur. Their chest and belly are pale gray-white in color.


Langurs are folivores (leaf eaters), which is why they are often referred to as leaf-monkeys. The Popa langur diet consists of 58.4% leaves, 24.4 % fruits, and 9.7% green shoots and petioles. All these hearty greens mean that these langurs need to spend a lot of time eating and digesting their food. They have a multi-chambered stomach that helps the gut bacteria break down the tough plant fibers. Langurs are also known to have large salivary glands that produce starch-digesting enzymes. 

Behavior and Lifestyle

These primates are arboreal (spending most of their time in trees) and diurnal (active during the day). The troop often clambers through the canopy using all four limbs and their long tail for balance. When they feed, they sit on a branch and reach out to select young tender leaves. Young langurs often jump playfully in the branches near the adults. 

They are capable of traveling long distances and can have home ranges as large as 256 acres (100 ha), but with deforestation and forest fragmentation, their home ranges have shrunk significantly.

Fun Facts

Popa langurs were discovered as a new species in 2020.

They were described as a new species after scientists genetically tested 100-year old museum skins. 

Young Popa langurs are pale white in color and spend the first year of their life clinging to their mother.

There are less than 250 individuals left in the wild. 

Daily Life and Group Dynamics

Once they wake up, Popa langurs start foraging to find a large enough source of nutritious leaves and fruits. Once langurs find a patch of young leaves or ripe fruit, they stay in that spot and eat as much as they can, selecting the best leaves from the tree. In this way they clear patches of leaves in the forest before traveling to the next patch.  

As the day progresses, it gets too hot to travel or be high up in the canopy for long, so they stop feeding for an afternoon rest period in the shade of the lower canopy.  

Langurs sub-adults spend a lot of time grooming each other. Grooming is not only a hygienic practice to remove parasites, but it also helps maintain bonds and social hierarchy. One monkey can gain favors, such as access to food, by grooming a more dominant monkey. 

The dominant male in the troop has the job of protecting the troop from predators and intruding males who want to displace him. As young males grow up and become sexually mature sub-adults, they are urged to leave the home troop as he may become a threat to the dominant male. This behavior also prevents males from mating with close relatives (such as aunts or cousins), which can cause genetic defects in the resulting offspring.

Females in the troop are usually closely related and do not have many antagonistic or violent outbreaks because competition for food or males is lower among females.


Langurs are vocal primates and have a range of calls to communicate with each other. They emit loud calls especially when defending their troops. Sharp high-pitched calls are used to warn troop members of predators nearby. Within a troop, soft chattering sounds are used during rest and play times to maintain contact with each other. 

Understanding the specific communication behaviors of the Popa langur would require more detailed research and observations in their natural habitat.

Reproduction and Family

Though we do not know the specific biology of Popa langurs (because of lack of studies), we assume that it is similar to closely related species. The general gestation period for the genus is about 205 days or about 7 months. The young are born with pale white to light yellow fur. The babies cling onto the belly of the mother for at least the first year of their life. While the white fur of the baby may seem to be extremely visible to predators, against the dark fur of their mother, the coloring acts as effective camouflage. If predators look up at them, they will see the white fur blend against the bright sky. And if a flying predator looks down, the baby is hidden under the dark furred mother who blends with the shadows in the canopy. Mothers are the primary caretakers as they feed, carry, and protect their baby. As the young become more independent they move away from their mother’s protection. Around this time, the white conspicuous fur color changes to the darker fur similar to the adults. 

They live in multi-female multi-male families with a dominant male that gets the largest access to food and females. Families or troops can consist of 8–30 individuals though, with the current low populations of Popa langurs, larger troops are seldom seen. 

Males become sexually mature around 4 years of age and move out of the natal troop they were born into. These males may join other males or try to challenge a dominant male of another troop so that he can establish his own troop and mate with females.

Photo: ©Htet Arkar Aung/iNaturalist/Creative Commons
Ecological Role

The specific ecological role of Popa langurs is difficult to specify because of their low numbers and severe habitat degradation. As folivores, langurs play an important role in controlling the number of leaves in a subtropical/tropical forest. In this sunny habitat, large trees tend to grow tall and spread out so they can expose the maximum number of leaves to sunlight. This increases the amount of food the leaves can make for the tree (through the process of photosynthesis). The unfortunate consequences of this is that shorter or younger trees often get shaded out and do not get access to sunlight, which limits their growth. As troops of langurs eat the leaves, they cut down the dense canopy and allow patches of sunlight to reach the lower levels of the forest and provide smaller plants the chance to photosynthesize food as well.

Conservation Status and Threats

The International Union for Conservation of Nature lists the Popa langur as Critically Endangered (IUCN, 2020), appearing on the IUCN Red List of Threatened Species.

Habitat loss and hunting are the biggest threats to their survival. Given their small population, even small changes in the population can have large effects on the langur’s ability to reproduce and maintain sustainable numbers. Currently, there are between only 135–250 individuals in the wild and their population is estimated to decrease continuously.

In Myanmar, as the local human population grows, the demand for space and lumber resources increases, leading to deforestation for human development and excessive lumber logging. The habitat loss is worsened by the soil and water pollution that is an outcome of more developed areas. Wildlife habitat in this region will have a difficult time recovering from the rapid environmental changes. 

There are also cases of primate hunting in general in South East Asia for bushmeat and illegal pet trades. It is likely that the Popa langur has fallen victim to this activity as well. Hunting usually takes out healthy adults from a population, which leaves fewer reproductive-aged adults in the system that can help maintain a healthy number of individuals. In this manner, hunting can have a severe effect on a population compared to diseases where the weaker members of the population are affected.

Conservation Efforts

The discovery of Popa langurs is so new and their population is so low that international regulations have not caught up with protection designations for the species. 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, lists many langurs under Appendix II, which protects them from international trade.

A sincere effort has been made to eliminate hunting and reduce logging activities in the area due to the new species designation and low population numbers. The Myanmar government has collaborated with international organizations to provide conservation strategies for the Popa langur. Mount Popa, a sacred pilgrimage site, is already protected against further development, and the law enforcement in protected areas has been enhanced to safeguard natural resources against poachers.

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Written by Acima Cherian, December 2023