Arunachal Macaque, Macaca munzala
ARUNACHAL MACAQUE
Macaca munzala
Geographic Distribution and Habitat
The Arunachal macaque, scientifically known as Macaca munzala, is a recently described macaque species (2005) located in the westernmost region of Arunachal Pradesh, a state in Northeast India. Arunachal Pradesh sits at the foot of the Himalayas and is considered a biodiversity hotspot, boasting an extensive number of nonhuman primates and many other mammal and plant species. The region consists of many different kinds of forests, multiple hill ecosystems, and an extensive river system.
Arunachal macaques reside in the higher altitudes of the region, up to 11,483 feet (3,500 m) and as low as 6,500 feet (2,000 m). The monkeys tend to localize around Zemithang in the Tawan district of the state. Within this district, Arunachal macaques can be found in a westernmost area called West Kameng and in other regions of Arunachal Pradesh that border Bhutan and Tibet.
Since the discovery of the Arunachal macaque in 2005, there have been numerous studies that debate its existence. Using DNA and morphological (structural and biological) evidence, these scientists have concluded that the Arunachal macaque is actually the Assam macaque (Macaca assamensis). Additionally, the lack of research on this species makes it so that the delineation between species remains unclear. Conversely, with the recent discovery of the Sela macaque (Macaca selai), that accepts and requires the existence of the Arunachal macaque, there may be more work published about the validity of the species.
Size, Weight, and Lifespan
Arunachal macaques are sexually dimorphic, with males larger-bodied and with longer skulls and canines than their female counterparts. Little is definitively known about their exact size and weight. With only one individual that has been measured and based on other macaque species, the generally accepted adult male weight lies around 33 pounds (15 kg), and length is measured to be about 32.4 inches (82.4 cm) in total length with a tail of 10.4 inches (26.4cm). Taking these measurements, females are assumed to be slightly smaller. The lifespan of these monkeys is not documented but can be assumed to be somewhere around 20-30 years in the wild and up to 40 in captivity, in line with other species of macaque.
Appearance
Arunachal macaques are said to resemble Tibetan macaques (Macaca thibetana) but are larger bodied and stouter with shorter tails than other macaque species. Their fur is a dark to chocolate brown color, getting lighter as it reaches the upper torso and the ends of limbs. This fur ranges from light brown to olive and reflects the color of their hands and feet. Fur is long and dense in the upper torso but gets shorter and smoother towards the lower torso and trunk. Tails are dark chocolate brown in adulthood, but juvenile Arunachal macaques have virtually no fur on their tails.
The Arunachal macaque is identified by a small patch of pale-yellow set in a dark patch of fur. This patch has been found to change seasonally, with the yellow patch disappearing in the summer months, leading researchers to believe that some of their appearance may change with the seasons. Some monkeys also have a spike of hair on their heads, while others have a whorl or tuft of hair.
Their faces are a darker brown than their coat color, with a prominent dark patch on either temple. Their upper faces are noticeably wider than their muzzle, and their dark ears can be seen easily through their shorter fur. In many monkeys, there is a dark line just above the eyes that is more obvious in juveniles. The monkeys also have lighter fur around their collar compared to the rest of their bodies.
Diet
Similar to many other macaque species, Arunachal macaques are opportunists; they get food wherever they can find it. While they may be mainly herbivorous, their diet changes with their environment. One study found that the number of plant species consumed in the spring increased from 18 to 25, and the general food types increased from 18 to 36. In the winter, due to the scarcity of diverse plant foods, 75% of the monkeys’ diets consisted of just 2 plant species. One such plant is called Erythrina (a tree from the pea family), which comprises 72% of their diet in colder months. In the spring, the plant only constitutes 19% of the diet as the spring diet has much more variety, including the fruits of the Elaeagnus parvifolia (also called the Autumn Olive). In short, Arunachal macaques increase diet diversity when the climate is warmer and more plants are available.
Aside from seasonality, Arunachal macaques also eat leftover human food found in human-populated areas with garbage cans and open markets. They will also participate in crop raiding, destroying and eating crops cultivated by the people that reside in their habitat.
Behavior and Lifestyle
Arunachal macaques are diurnal, meaning they are active during the day. During the day, they will spend a considerable amount of time foraging. One study observed that for 48% of their day, Arunachal macaques were found moving and foraging for food. In the colder months, the monkeys actually prefer feeding more, with up to 66% of their day preoccupied with their diet, compared to the warmer months. This increase in food attention when it’s cold could be attributed to the decreased biodiversity in colder weather or due to the need for more food during the winter. In other words, with less food available, monkeys need to spend more time searching for it, or they simply need more food to handle the harsh temperatures. Their other behaviors are also dependent on seasonal changes. While this study found that Arunachal macaques spend 36% of their day sitting and resting and 16% reserved for social interactions, in the warmer months, up to 51% of their day is dedicated towards both rest and movement. Across the board, they spend a lot of time and energy on searching for and consuming food, while spending a little less of their day resting and interacting with groupmates.
While they spend a majority of their day foraging on the ground, they tend to prefer the limbs of trees in the evening, resting in trees approximately 50 feet (15 m) above the ground. Like other macaque species, Arunachal macaques are quadrupeds (walking on all fours), having the ability to traverse across the ground and trees.
Local people call the Arunachal macaque Borang-Zala (Tshangla language: Forest Monkey), and Mun-Zala (Dirang Monpa language: Deep Forest Monkey)
1.96 million years ago, the Arunachal macaque population was split by the Sela mountain pass in Arunachal Pradesh. On one side of the pass, the Arunachal macaque evolved into the monkey we know today, but on the other side of the pass, the recently discovered Sela macaque (M. selai) had evolved.
Arunachal macaques are not unlike other types of macaques. They spend time looking for food, foraging, resting with friends, and interacting with groupmates. Groups can range from anywhere between 5 and 60 individuals, but typically fall around 20 monkeys. On average, the troops are 30.37% juveniles, 23.83% adult females, 18.22% infants, 11.53% adult males, 9.81% sub-adult females, and 6.23% sub-adult males. These groups are multimale and multifemale and are relatively peaceful. Aggressive interactions may occur, but the social hierarchy is not built on intimidation and aggression like some other macaque species. That said, while aggression isn’t holding a hierarchy together, a lot of the structures are similar across other macaque species. Arunachal macaques forge bonds through grooming and follow a matrilineal group structure, with the mother determining the status of the offspring.
Groups are clearly delineated socially amongst the species, but home ranges may overlap. Home ranges typically span from 17 to 136 acres (7–55 ha) with an average of around 40-70 acres (16-28 ha). When ranges do overlap, interactions are typically peaceful.
The Arunachal macaque communicates similarly to other macaque species, using body language, vocalizations, and facial expressions to communicate threats, food, or friendliness. While there have been no direct sources observing vocalizations from these monkeys, they are likely to follow similar vocalization patterns of other macaque species. However, there have been observations of facial expression, posturing, and object manipulation in the population that closely resemble other macaques. Whether they be used to indicate a threat, signal aggression, or yield in submission, a combination of all of these communication skills are employed on a regular basis. One of the most commonly observed activities is grooming, an affiliative behavior meant to strengthen bonds and communicate attachment and connection.
There have been no direct observations on reproduction in the Arunachal macaque, but it is appropriate to say their reproduction closely resembles other macaque species.
Macaque gestation periods range from 150-190 days, and a female may birth once every two years, typically with one or two infants at a time. Macaques also generally reach weaning at about the first year and reach sexual maturity in females between 2.5 to 3.5 years, with males maturing at 3 to even 6 years of age.
Arunachal macaques, following a similar social structure to other macaques, most likely have the mother as the primary caregiver. The mother will feed, groom, and ensure the baby’s survival until the baby can live on their own. In many macaque species, alloparenting, when other females take care of young, is present but has not yet been identified in the Arunachal macaque.
Arunachal macaques are herbivorous, meaning the seeds they pass through digestion from the fruits they eat inevitably end up on the forest floor. They are participating in the biodiversity of Arunachal Pradesh. While many predators live in Arunachal Pradesh, such as dholes (Cuon alpinus), Asiatic black bears (Ursus thibetanus), and snow leopards (Uncia uncia), none are recorded to actively prey on specifically Arunachal macaques, but have been found to eat other monkeys before.
The International Union for Conservation of Nature lists Arunachal macaques as Endangered (IUCN, 2015), appearing on the IUCN Red List of Threatened Species.
A study in 2008 showed 35 active and distinct troops populated with 569 individuals. Since then, another study has claimed there may be fewer than 250 mature individuals. Little is known about the exact number of Arunachal macaques that live in Arunachal Pradesh, but evidently, the population is declining and will most likely continue to do so.
The biggest threat to the Arunachal macaque comes in the form of retaliatory killings and some hunting by humans. Arunachal macaques are known to raid crops alongside other macaque species residing in Arunachal Pradesh. They are extremely destructive, causing financial distress and economic loss to farmers. In retaliation, Arunachal macaques are killed with snares, bows, or guns.
Aside from retaliatory killings, Arunachal macaques are sometimes hunted. While the trade of Arunachal monkey meat does not appear to exist, some non-local government employees will engage in hunting.
With both of these combined, one study found that in one year, one village killed 54 Arunachal macaques, causing a devastating blow to an already dwindling population.
Arunachal macaques 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.
Arunachal macaques have not been directly observed on protected land, but it is uncertain whether they are present in Mouling National Park.
Since their discovery, there have been many recommendations to reduce the number of retaliatory killings and efforts to encourage a peaceful coexistence in human-populated areas. It has yet to be seen what the exact effects of these efforts on the Arunachal macaque population are, but they are most likely decreasing the number killed each year. While this is a step in the right direction, scientists are still encouraging more community and conservation plans that have yet to be put in place.
- Arunachal Pradesh Wikipedia
- Macaca munzala Animal Diversity Web
- New macaque species discovered in Arunachal Pradesh, Nature.com
- IUCN redlist Arunachal macaque
- Uttara Mendiratta, Ajith Kumar, Charudutt Mishra, Anindya Sinha. Winter ecology of the Arunachal macaque Macaca munzala in Pangchen Valley, western Arunachal Pradesh, northeastern India. Am. J. Primatol. 71:939–947 (2009). https://doi.org/10.1002/ajp.20734
- Ghosh A, Thakur M, Sharma LK, Chandra K. Linking gut microbiome with the feeding behavior of the Arunachal macaque (Macaca munzala). Sci Rep. 2021 Nov 9;11(1):21926. doi: 10.1038/s41598-021-01316-0. PMID: 34754005; PMCID: PMC8578487.
- Kumar, R. S., Mishra, C., & Sinha, A. (2007). Foraging ecology and time-activity budget of the Arunachal macaque Macaca munzala – A preliminary study. Current Science, 93(4), 532–539. http://www.jstor.org/stable/24099220
- Sinha, A., Datta, A., Madhusudan, M.D. et al. Macaca munzala: A New Species from Western Arunachal Pradesh, Northeastern India*. Int J Primatol 26, 977–989 (2005). https://doi.org/10.1007/s10764-005-5333-3
- Sarania B, Devi A, Kumar A, Sarma K, and Gupta AK. Predictive distribution modeling and population status of the endangered Macaca munzala in Arunachal Pradesh, India. Am J Primatol. 2017; 79:e22592. doi:10.1002/ajp.22592.
- Avijit Ghosh, Mukesh Thakur, Sujeet K. Singh, Ritam Dutta, Lalit K. Sharma, Kailash Chandra, Dhriti Banerjee, The Sela macaque (Macaca selai) is a distinct phylogenetic species that evolved from the Arunachal macaque following allopatric speciation, Molecular Phylogenetics and Evolution, Volume 174, 2022, 107513, ISSN 1055-7903, https://doi.org/10.1016/j.ympev.2022.107513.
Written by Nami Kaneko, Jul 2025