ASSAM MACAQUE

Macaca assamensis

Geographic Distribution and Habitat
The forests of southeast Asia are home to the Assam macaque (or Assamese macaque). Their homes span over nine countries from Vietnam to Nepal. In Tibet, they are also known as Himalayan macaques or hill monkeys.

These Old World monkeys live in all types of dense primary forests, from the dry to the tropical. They move both through the trees and on the ground, and live on mountain ranges from the Himalayas to the limestone cliffs of Nongangg, China.

While they live in a variety of lowland and highland types of forest, they have not adapted to live in secondary forests or disturbed habitat. They have been known to frequent semi-provisional protected sites (where humans have altered the landscape) such as temples.

Subspecies are the eastern Assam macaque (M. a. assamensis) and western Assam macaque (M. a. pelops), which have different distribution ranges separated by the Brahmaputra River.

Assam macaque range, IUCN 2020

Size, Weight, and Lifespan
Certainly not the largest species of macaques, Assam macaques are about the size of small to medium dogs. Sexually dimorphic, males can range up to 28.7 in (73 cm), females to 23 in (59 cm). Males weigh between 22 and 32 lbs, (10–14.5 kg) and females between 17 and 26 lbs (8–12 kg).

Eastern Assam macaques have shorter tails than western Assam macaques, but for both it averages around half the length of their body. The tail length is unique to the individual.

They have been known to live up to 31 years in captivity, but their longevity in the wild is unknown. Similar macaque species often live to be over 20 years old in the wild.

Appearance
Adults have red skin, which can give their hairless face a red-purplish hue. They have amber or light green colored eyes. Their pelage can be any combination of golden, reddish, light grey, or dark brown. They often have white fur on their bib and belly. Some appear to have the hair on their head parted in the middle. They have faces more expressive than some movie stars.

Photo credit: Rachid H/Flickr/Creative Commons

Diet
Eating everything from fruit to 55 types of leaves, seeds, bark, and flowers, these macaques will adjust their diet based on their habitat. Opportunistic eaters, they technically are omnivores.

In areas where fruit is seldom available, Assam macaques eat mostly new leaves. In areas where humans may feed them (such as in temple sites), they eat what humans give them more than what they can forage naturally. Where human agriculture has impacted their habitat, they have been known to raid crops (corn, oats, wheat). 

One study, noting the difference between wild and semi-provisional groups, found that wild macaques ate mostly fruit, whereas the semi-provisional ate primarily human food. In areas where humans are interacting with this wild species, there can be interspecies conflict and the possibility of disease transmission. The conflict and the possibility of contagion goes both ways, both for humans and macaques.

Like other species of macaque, Assam macaques have cheek pouches in which they store food to eat later, so they may shove way more in their mouth than they can eat at one time.

 

What Does It Mean?

Disturbed Habitat:
A temporary change in environmental conditions that causes a pronounced change in an ecosystem.

Frugivore:
An animal who feeds on fruits.

Folivorous:
Having a diet that consists of leaves.

​​Natal group:
The group into which an animal is born.

Old World monkey:
Monkeys native to Africa and Asia.

Omnivore:
An animal or person who eats food of both plant and animal origin.

Pelage:
The fur, hair, or wool of a mammal.

Polygynandry:
A mating system in which both males and females have multiple mating partners during a breeding season.

Primary forest:
Also termed old-growth forest, virgin forest, or primeval forest—a forest that has attained great age without significant disturbance and thereby exhibits unique ecological features and might be classified as a climax community, an ecological community in which populations of plants or animals remain stable and exist in balance with each other and their environment.

Secondary forest:
A forest that has regrown after a major disturbance, such as fire or timber harvest, but has not yet reached the mature state of primary forest.

Sexually dimorphic:
When males and females have different characteristics (size, color, etc.) other than their reproductive organs.

Subcaudal:
Situated under the tail.

​​Vestigial:
A part of the body that in the course of evolution, has degenerated and become functionless; the last small part that remains of something that once existed.

Visit the Glossary for more definitions

Behavior and Lifestyle
​The Assam macaque works during the day and sleeps at night. They are primarily arboreal, spending most of their time up in the trees—but they can also walk on the ground when necessary, on all fours (quadrupedally). They tend to travel less than other macaques and stay closer to their home range. Their daily work is finding food, which is the primary activity. Resting is also vital; they spend a fair amount of time taking a break between grooming, traveling, playing, and dealing with the drama of conflict and sexual behaviors. Like the characters in a high school drama, maintaining important social connections is a way of life.

Daily Life and Group Dynamics 
It’s safe to say that the social hierarchy for all primates is a relatively complex system with somewhat baffling rules to the non-initiated. The macaque is no different. Scientists using all types of theoretical models try and decipher the codes of macaque interactions.

However, it is possible—maybe even probable—that observation changes behavior. Assam macaques, with their tendency to generally keep away from disturbed habitats or secondary forests, may have different behavior when they are observed by researchers studying populations near religious temples or protected areas frequented by humans. Thus, it is important to note that in describing some of the more detailed observations of daily life and the group dynamics of Assam macaques that these are groups that are more habituated to humans.

All macaques are matrilineal—meaning that hierarchy is based on a female-determined family structure that continues through generations. While it does not appear that there is one dominant female, there are dominant families led by females. Assam macaques live in multi-female, multi-male groups (known as troops), which can number as high as 50 individuals. Depending on the subspecies and habitat, the average number in a troop varies either between 10 and 15, or in the mid 20s. Females stay in their natal group for life. Younger females of dominant families have more social standing than older females from subordinate families, and the older females may defer to the younger with greater position. Younger males, however, are generally subordinate to older males, regardless of family. Males, unlike females, leave the group to which they were born when they reach maturity.

When there is conflict between group members, they may show signs of stress by taking time to themselves and abstaining from group activities. Reconciliation, when it happens, is offered by the aggressor. Females show a tendency to reconcile more frequently with females with whom they have a prior relationship, or have a positive social position, while males may reconcile regardless of prior relationship or social standing.

It is rare that macaques form interspecies groupings, but in a recent (June 2019) case, Assam macaques had formed a troop with male rhesus macaques. The rhesus spent more time foraging for food on the ground, whereas the Assam macaques spent more time in the trees and cliffs, meaning they didn’t necessarily compete for food. Also, while the rhesus seemed interested in female Assam macaques, this feeling was not reciprocated. There was no inter-breeding. The rhesus and Assam macaques were group buddies, benefiting both species by providing more protection for potential predators.

Communication
Communication in all primates is multi-sensory. Using gestures, facial expressions, voice, smells, and touch, macaques communicate everything from familial affection to place in a social hierarchy. Like all macaques, the Assam macaque has a wide variety of call types. The most frequent types are contact calls (like: “Hey, where you?” “Up here!”). They have vocal calls identified for within the species, outside the species, when infants are weaning, and when they are angry, playful, or any rainbow of emotions. They also communicate much through their facial expressions.

Facial expressions can mean different things to macaques than they do to humans, but they are very different expressions than those that have evolved in human culture. In tourist locations this has led to some trouble where humans try to interact with or feed them: What can be interpreted as smiling or blowing kisses can actually mean “get away or I’ll bite you.”

One study found that the more facial expressions exhibited, the more tolerant the species of macaque. The particular facial expressions of Assam macaques in their natural environment are not widely observed, but with the more relaxed dominance style of this species, it is safe to say that they, like all macaques, have an incredible variety of expressions by which they communicate based on the complexities of their relationships.

Reproduction and Family
Reaching sexual maturity at 5 years of age, males leave the group in which they were born while females stay. Males leaving their natal group to join a different troop helps to prevent in-breeding and assures more diversity of partners. In their mutli-male, multi-female troops, Assam macaques are polygynandrous.

Females have subcaudal swelling during menstruation, but it is less pronounced in Assam macaques than other species of macaque. Furthermore, the size or visibility of swelling has not been found to have any bearing on status or fertility. One study surmised swelling might be a vestigial trait that is no longer relevant.

Breeding for the Assam macaque is seasonal, but that season depends on the location of the troop. Generally, breeding falls in between October and February. After a gestation period of 165 days, mothers have one offspring weighing about 14 oz (400 gm). Infants are born between April and June. Time interval between births varies between 14 and 23 months.

Males are very invested in caring for the infants. Males may form strong relationships with females and associate with the raising of the infant for more than one breeding season—even though there is no guarantee that they are the parent of the offspring. Males form relationships with infants and can be protective of them against others in the group and may behave as if they are the father, and have success in breeding in further seasons. Or, a male may form a relationship with a mother and her infant one season and this will lead to breeding in subsequent seasons. Scientists, like the rest of us, refer to this as a “friends with benefits” scenario.

Photo credit: Charles J Sharp/Creative Commons

Ecological Role
The diet of the Assam macaque varies according to their habitat. They can be mainly frugivores or consume mostly new leaves (showing folivorous tendencies). Their consumption of what food their habitat has to offer and returning it to the earth in the form of a perfectly fertilized seed (i.e., pooping seeds) makes them essential to the growth and health of the forest.

Conservation Status and Threats
The Assam macaque is listed as Near Threatened by the International Union for the Conservation of Nature (IUCN, 2015), appearing on the IUCN’s Red List of Threatened species, with populations decreasing. Even over their wide distribution of habitat, Assam macaques are threatened over most of their range. More than half the populations live outside protected areas.

The largest contributing factor to their decreasing population is habitat loss due to logging and commercial and residential development—but there are other factors as well. They are hunted where they may disturb crop yields. Their skulls were observed in the front of houses in northeastern India as presumed talismans to ward away the “evil eye” against the household.

The Nepal population of Assam macaques is already considered Endangered as they are living in a smaller and fragmented patch of land and already battling dwindling numbers.

In Thailand, Assam macaques are only protected in temples (where they may interact with humans).

They are hunted for their skin in Myanmar. People use the skin of these incredibly social primates to make footwear and accessories. Also in Myanmar, a 30% decrease in forest cover over the past 30 years has led to a terrible loss to this macaque’s habitat.

In Laos PDR and Vietnam they are hunted for food and to make glue and a medicinal balm. The population has decreased over 35% and is expected to continue to decrease (again, the last assessment was in 2008).

They are also threatened by invasive species and diseases.

Conservation Efforts
Assam macaques are listed in the 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 wild animals and plants does not threaten their survival. Assam macaques are legally protected in every country in which they live. While legal protection may not mean much as far as actually preventing them from being hunted, it is at least a start.

Assam macaques have been seen in at least 41 different protected areas or parks, and there are current calls for more areas of protection.

More studies are being conducted about the Nepalese population of Assam macaques, which are under the greatest risk of extinction, in order to better conservation efforts.

References:

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Written by Laura Lee Bahr, June 2020