Assam Macaque, Macaca assamensis
ASSAM MACAQUE
Macaca assamensis
Geographic Distribution and Habitat
The Assam macaque, also known as the Assamese macaque, and scientifically as Macaca assamensis, is a monkey from South and Southeast Asia. It inhabits the countries of India, Nepal, Bangladesh, Bhutan, China, Laos, Myanmar, Thailand, and Vietnam. Most specifically, the monkey is found east of the Brahmaputra River, in southwestern China (west and south of Yunnan), northeastern India (eastern Arunachal Pradesh, eastern Assam, Nagaland, Meghalaya, Manipur, Mizoram, Tripura states), eastern and western Myanmar, northern and western Thailand, Laos, and northern Vietnam. The monkeys have also been observed in the north along the Dihang River and its Tibetan tributary, the Ngagong.
There are two known subspecies: the Eastern Assamese macaque (Macaca assamensis pelops) and the Western Assamese macaque (Macaca assamensis assamensis), inhabiting the eastern and western portions of this range. The monkeys inhabit a range of altitudes from 656 to 9,022 feet (200 to 2,750 m), with some reaching up to 13,123 feet (4,000 m), showcasing their wide adaptability.
Assam macaques prefer dense forests, but have also been recorded in tropical and subtropical semi-evergreen forests, dry deciduous, and montane forests. While they can inhabit lower elevations, the western monkeys prefer higher land and seldom find a home in places lower than 3,281 feet (1000 m). In the wetter climates of the east, Assam macaques also prefer higher altitudes, with groups never going below 1,640 feet (500 m). In Laos and Vietnam, however, the monkeys prefer much lower altitudes from 656 to 1,312 feet (200-400m).
There are two subspecies of the Assam macaque, the Eastern Assamese macaque (Macaca assamensis pelops) and the Western Assamese macaque (Macaca assamensis assamensis). Primarily differentiated by their geographic distribution, the subspecies look quite similar to one another with one distinction: the Western Assamese macaque’s tail is much shorter than the Eastern Assamese macaque.
More research is needed to clarify the taxonomic status of some groups of Assamese macaques, particularly those in Arunachal Pradesh, India. Three different species have been named for groups of macaques in this province: the Arunachal macaque (Macaca munzala), the white-cheeked macaque (Macaca leucogenys), and the Sela macaque (Macaca selai). The IUCN Red List recognizes two of these species (M. munzala and M. leucogenys), though more work is needed to understand the relationships between these populations.
Size, Weight, and Lifespan
Assam macaques are sexually dimorphic, meaning males are larger than females. Interestingly, females of the Eastern Assamese macaque subspecies are smaller than Western Assamese macaque females.
The head-body length of a typical male Assam macaque can fall anywhere from 21 to 28.7 inches (53.2 to 73 cm), with an average of 24.3 inches (61.6 cm). The tail of the Eastern Assamese macaque tacks on another 7.5 to 9.8 inches (19 to 25 cm), with the Western Assamese macaque almost doubling in tail length at 10.6 to 18.1 inches (26.9 to 46 cm). The smaller Eastern Assamese female macaque measures in at about 17.2 to 22 inches (43.7 to 55.5 cm) with the tail an additional 6.7 to 8.9 inches (17.0 to 22.5 cm). The Western Assamese macaque female is 20.86 to 23.1 inches (53 to 58.7 cm) with a tail of 10.4 to 14.5 inches (26.5 to 36.98 cm).
The Western Assamese male macaque weighs in at about 22.9 to 25.3 pounds (10.4 to 11.5kg), and their females at 17.5 to 19.3 pounds (7.8 to 8.75kg). The Eastern Assamese male macaque has been recorded to be 17.4 to 36.4 pounds (7.90 to 16.50kg), with females weighing 10.8 to 19.4 pounds (4.9 to 8.8kg).
Assam macaques can live up to 31 years in captivity, but their lifespan in more natural settings has yet to be studied. Similar macaque species typically live 20 years in the wild.
Appearance
With golden brown to chocolate fur, Assam macaques vary in appearance. Some monkeys can look golden with lighter, pale fur, while another group can have darker, richer coloration. Their eyes can range from lighter green to amber. The pelage on their back is dense and fluffy, while their underside is sparsely covered with their pale, bluish skin peeking through. On the crown of their head, the fur can be smooth, tufted, or even form a little cap. The T-zone of their face, eyes, nose, and mouth, is quite bare but with prominent whiskers on their cheeks and chin.
Diet
A little less than half of the Assam macaque’s diet comes from fruits. Animal matter, like insects and lizards, is also consumed alongside leaves and some flowers. Macaques are notoriously adventurous eaters, adjusting their eating habits to their environment and seasons.
Assam macaques that live in human-populated regions consume fruit crops such as banana, orange, apple, mango, guava, papaya, lychee, cucumber, and tomatoes. Other items, such as bread, biscuits, snacks, rice, grams, groundnuts, and molasses, which are not naturally acquired, are either given by or stolen from people. Despite some reliance on crops, Assam macaques still prefer natural foods, plucking fruits from trees and breaking branches to reach their precious food sources.
Assam macaques, like all other members of their subfamily, have cheek pouches that allow them to store food long after they’ve put it in their mouths. This is a very effective form of food storage, allowing for multiple meals to be saved by shoving it in their mouths during one sitting!
Behavior and Lifestyle
Assam macaques are both terrestrial and arboreal, meaning they live on the ground and in the trees. However, Assam monkeys typically prefer their arboreal lifestyle but will descend to the ground when raiding human crops and encountering environments with fewer trees.
The monkeys are diurnal, meaning they are active during the day and sleep at night. Where and how they sleep is highly variable depending on their environment. In the limestone forests of Southwest Guangxi, China, monkeys make sleeping sites on cliffs. They have preferences for sleeping sites, but never use them more than a couple of times in case a leopard uncovers their location. Since they are vulnerable when asleep, Assam macaques have to pay close attention to where and how many times they sleep in a given sleeping site. These Assam macaques use their sleeping sites to avoid predators in addition to staying close to resource patches.
During the day, they spend the majority of their time feeding, traveling, resting, and grooming. In areas with more people and therefore more accessible food sources, the monkeys will redistribute their time to include less feeding and emphasize other activities like resting, traveling, and socializing. In the same population of Assam macaques in the limestone forests of China that sleep on cliffs, in seasons when fruit is abundant, these monkeys travel longer distances than in seasons when fruit is less common.
The Assam macaque is the most common and widespread monkey in Bhutan.
In Thai, the monkey is called ลิงอ้ายเงี๊ยะ or phonetically spelled: Li ngx̂āyngeī́ ya.
Assam macaques are social monkeys with multi-male and multi-female groups as large as 50 individuals, but averaging at about 20. The groups are governed by matrilines, meaning that families headed by females dictate the social hierarchy. Inside the social hierarchy, females of higher-ranking families tended to have access to higher-quality resources, and younger females of the matriline typically outranked the older females. Males tend to groom females more than the other way around, indicating that males try to win the favor of females. And rightfully so! If they had offspring with high-ranking females, their children would gain access to better resources.
Something that promotes social hierarchy stability is grooming. Assam macaques are social groomers, meaning to make nice, they will pick and poke at each other’s fur to rid their friends of parasites or bugs. Many scientists consider grooming as a form of “social currency”: an I-groom-you-so-you-groom-me system. This helps solidify the social hierarchy and enables interactions with group mates that don’t require resources like food or space, which can quickly turn sour.
While matrilines structure the overall social hierarchy, age is an important factor among males, with juveniles and adults exhibiting notably different behaviors. When a male Assam macaque reaches sexual maturity and enters adulthood, he leaves his natal group. In search of a new group, he may travel long distances before joining another group, where he begins at the bottom of the social hierarchy. Females, by contrast, remain in their natal groups throughout their lives and occupy stable positions determined by their mothers’ status.
Assam macaques live in regions that support many other nonhuman primate species, including several macaque species. In India, they are often confused by hunters with the rhesus macaque and may occur in areas where multiple macaque species overlap. Although Assam macaques rarely interact directly with other primates and typically reduce competition by relying on different food resources, there have been documented cases of individual rhesus macaques following Assam macaque groups. In 2025, scientists suggested that this unusual behavior may help rhesus macaques avoid shared predators, particularly leopards. By moving within Assam macaque groups, these bachelor males may reduce their risk of being targeted by predators.
Assam macaques, like many other macaque species, are strong communicators, employing a myriad of vocalizations, facial expressions, and body language to communicate with each other.
Assam macaques are talkers! One study found that the monkeys produced 12 different types of calls in order to communicate within their group, outside of their group, and with other species. Contact calls, or a call signifying you-see-me-I-see-you, were most commonly observed at 25.2%, followed by aggression calls at 19.9%. Submission calls, which are used when a lower-ranking monkey is on the other end of a higher-ranking monkey’s aggression call, were at 18.2%. Weaning calls, used by babies starting to learn to live on their own, accounted for 10.3% of all the calls of the group. Alarm calls, which are super important when communicating a threat, were at 7.8%. Food calls, for when monkeys are extra hungry (5.1%), and affiliation calls (5.0%), comprised just over 10% of all calls. The last 8.5% of all vocalizations from the group were calls for affiliation, copulation, and play.
To accompany their colorful language, Assam macaques also have a repertoire of facial expressions. Making eye contact, baring teeth, and lip smacking are all instances of communicating with group mates.
Eye contact with an open-mouth gape is used as a challenge, usually followed by an aggression call; it’s an invitation for a fight. The receiver of such animosity would typically respond with a submission call and teeth baring as a way to indicate their subordinate position and stop a fight from breaking out. Lip-smacking is a way of making friends. Assam macaques are social animals and use lip-smacking to break the ice. Younger monkeys will lip smack with each other, and males may lip smack with females and vice versa.
Many of their facial expressions that can come off as aggressive also end up becoming affiliative based on the context of their interaction. One study found that after teeth chattering, an open-mouth facial expression, eyebrow raise, bared teeth, and lip smack were to follow. They found that these facial interactions were 56.2% of the time more likely to be associated with affiliative behaviors rather than aggressive behavior (43.8%). Overall, Assam monkeys can’t hide their expressions and use them as a way to convey important information.
Body language is also a great way to communicate. Posture is indicative of how ready a monkey is to fight. Just as we see people square up to prepare themselves for a boxing match, monkeys will make themselves look big before getting aggressive. Assam macaques also use their body to ask for grooming sessions by placing themselves in front of friends, with arms spread wide, ready to be groomed. They can also show their rear as a way of showing subordination, and dominant males will “mount” males that are subordinate to them. These are all ways that monkeys communicate and solidify their social hierarchy.
Reproduction is very seasonal for the Assam macaque. The time period of conceptions lasts through the winter months, with the majority confined to December and January. Births occur from April to June. Female age at first birth can range from 3.5 to 6.5 years, with an average of about 5 years old. Gestation, or pregnancy, lasts on average 164 days until the mother gives birth to a baby weighing in at about 14 ounces (400 g). The period between births for the mom is either one or two years.
Sexual swellings are very common among female Afro-Eurasian primates and are typically an indicator of reproductive status or fertility, but Assam macaques do not exhibit prominent sexual swelling patterns. However, the variation in these patterns varies significantly. Some monkeys show extremely prominent redness on their bottoms, while others show none at all. A study found that this had little to no bearing on their reproductive success, or how likely they were to reproduce.
Alloparenting exists in this species, meaning monkeys, other than the mother, help take care of her young. Males will even step in to take care of offspring that they don’t even know are their own. Because Assam macaques are polygynandrous, meaning both males and females will have multiple mating partners, the father is often unsure of who his genetic offspring are. Even with this ambiguity, Assam macaque fathers work to take care of offspring in the group just in the hopes that it’s their child.
Since Assam macaques eat fruits, they redistribute the seeds after consumption in the poop they leave behind. By eating insects and other animal prey, they help to keep populations of these in check so they don’t become pests. The other foods they consume turn into fertilizer after their body have processed them. The things Assam macaques leave behind in their habitats are crucial for maintaining biodiversity and a healthy ecosystem.
The International Union for Conservation of Nature lists the Assam macaque as Near Threatened (IUCN, 2015), appearing on the IUCN Red List of Threatened Species.
The population of the Assam macaque has decreased significantly over the last couple of years, with the IUCN Red List citing that in 2015, the Assam macaque population decreased by 20-25% with varying effects across regions. Monkeys in China and Myanmar experienced an almost 30% decline in their population, while their friends in India experienced a loss under the 30% mark, causing the overall percentage to equate to 20-25%. Since the study in 2015, the threats to their habitat and wellbeing have not ceased and continue to forcibly decrease the population.
Habitat loss is one of the greatest threats to the conservation status of these monkeys. One study from 2023 predicts that by 2070, almost 57% of the current suitable habitat for Assam macaques in the eastern regions will be gone, causing devastating effects on an already declining population. In all the locations where Assam macaques can be found, habitat loss occurs due to agricultural activities, mining, and rapid developmental activities, all in tandem with other regional threats.
In Myanmar, Laos, and Vietnam, these monkeys are hunted extensively for their skins and bones to create footwear or medicinal balms. These are lucrative sources of trade in these countries. In some cases, Assam macaques are hunted accidentally. People can legally hunt rhesus macaques in many countries where the Assam macaque resides, but due to similarities in fur coloration and size, mistakes are often made. Hunting and poaching of these animals pose a great threat to their populations. Already weakened by habitat loss, the active hunting of monkeys destabilizes social groups and decreases mating possibilities, causing lasting effects across generations.
The Assam macaque 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.
Assam Macaques are legally protected in all the countries in which they occur. In India, the Assam macaque is listed under Schedule II, part I of the Indian Wildlife (Protection) Act. In Bangladesh, it is listed as Schedule III in the Bangladesh Wildlife Preservation Amendment Act of 1974. In Myanmar, it is legally protected according to the 1994 Wildlife Protection Law. In Thailand, the species is protected by the Wildlife Protection Act of 1960. In Nepal, it is protected under the National Parks and Wildlife Conservation Act of 1973.
The Assam macaque is also found in many protected areas. Although most are found in India due to the protection and food they receive at temples, the monkeys also reside in protected areas of Thailand, Laos, Nepal, and Vietnam.
Even while residing in these protected areas, habitat loss and poaching still cause devastating effects on their populations. Scientists urge more widespread education on this species, especially in order to stop the misidentification of the species while hunting.
Many private conservation efforts and foundations have been turning their efforts towards this species as well; one example is the Rufford Foundation, which has been assessing the population in Langtang National Park, Nepal.
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Written by Nami Kaneko, Dec 2025