Southern Pig-Tailed Macaque, Macaca nemestrina
SOUTHERN PIG-TAILED MACAQUE
Macaca nemestrina
Geographic Distribution and Habitat
Southern pig-tailed macaques (Macaca nemestrina), also known as Sunda, or Sundaland pig-tailed macaques, are South-Asian primates indigenous to Indonesia, Malaysia, Thailand, and Brunei. Introduced populations are also found on Tioman Island, the Natuna Islands, and Singapore.
Due to their proximity to the equator, Indonesia, Malaysia, Thailand, and Brunei experience consistently high temperatures and humidity. For instance, average daily temperatures typically range between 80 and 90 degrees Fahrenheit (26.6 to 32.2 degrees Celsius), and humidity levels fluctuate between 60 and 90%. The warm ocean waters surrounding these areas also lead to high evaporation rates, resulting in moist air and frequent heavy rainfall. Most precipitation occurs during the monsoon season, from June to September, and the seasonal wind pattern maintains tropical conditions.
While they naturally occur in lowland primary, secondary, coastal, swampy, and montane forests, they thrive in lowland and hill dipterocarp forests. Dipterocarp forests are tropical forests dominated by large trees of the family Dipterocarpaceae. In mountainous regions, southern pig-tailed macaques can be found up to 6,233.6 feet (1,900 meters), but they prefer drier, forested areas at the base of hills and slopes.
They can also be found near agricultural areas and on the edges and fringes of urban environments, which are strongly affected by habitat destruction and displacement. Although their geographic range is quite large, Southeast Asian ecosystems are rapidly declining, and the areas these primates occupy are heavily fragmented.
Before they were described as a full species in the early 2000s, southern pig-tailed macaques were considered a subspecies of Macaca nemestrina, which also included northern pig-tailed macaques (M. leonina) and Pigai Island macaques (M. pagensis).
Research suggests that they migrated to the Malay Peninsula from mainland Asia roughly 32,000 years ago. Over many generations, they spread into the surrounding areas of Southeast Asia, including Indonesia, Malaysia, Thailand, and Brunei.
Recent studies suggest that populations extending further into new territory are genetically distinct from the initial population. These findings hint at the existence of an unidentified southern pig-tailed macaque subspecies, but studies are needed to confirm these relationships.
Size, Weight, and Lifespan
Southern pig-tailed macaques are sexually dimorphic, meaning there are significant physical differences between males and females of the same species. Specifically, females tend to be lighter and smaller than males. Adult males have an average body length of 20.8 inches (52.4 cm) and weigh 13.7 to 32.0 pounds (6.2 to 14.5 kg). Adult females have a body length of around 18 inches (45.7 cm) and weigh between 10.4 and 24 pounds (4.7 and 10.9 kgs). Males also possess significantly larger canine teeth, measuring about 0.5 inch (1.2 cm), which they utilize as defensive tools during aggressive interactions.
In the wild, individuals typically live to about 26 years. Under highly managed captive conditions—such as in well-resourced, professionally run institutions—some individuals have lived to 35 years.
Appearance
As their name implies, southern pig-tailed macaques are uniquely recognizable by the way their tails resemble a pig’s, curling outwards and remaining half-erect at all times. It is black in color with a tan underside. These stubby tails are not prehensile, meaning they cannot grasp branches or other objects.
They have thick, layered black fur on their backs, featuring olive and brown color variations. Their undersides are covered in thinner, cream or white fur. At the top of the head, a dark brown to black patch of fur forms a noticeable crown. Because it contrasts with the lighter grayish-olive fur of the cheeks and forehead, it creates the appearance of a natural cap resting on the head. Their ears are slightly pointed and blend with the surrounding facial fur rather than standing out in a contrasting color. Their eyes are a beautiful shade of honey brown.
Extending from their mouths to their necks, southern pig-tailed macaques have internal cheek pouches that hold roughly the same amount of food as their stomachs! Serving as a hands-free way to transport food, this adaptation allows them to consume preferred resources away from potential predators or competition.
Diet
As omnivores, southern pig-tailed macaques have a diverse diet consisting of plants and animals. That being said, they typically consume more plants. Animal products are opportunistically consumed when preferred vegetation is unavailable, or to fulfill nutritional needs and supplement their diet with protein.
Like humans, macaques have trichromatic vision. This capability allows them to differentiate between red and green colors, which is especially important for foraging. Particularly when searching for ripe fruits, enhanced detection of red or orange food items against dense, complex foliage that would otherwise camouflage them is critically important to their survival.
In peninsular Malaysia, they eat wild ripe and unripe fruits such as mangoes (Mangifera indica), wild figs (Ficus carica), rambutan (Nephelium lappaceum), durian (Durio zibethinus), and terap (Trapa natans). They also eat plant shoots, stems, leaves, flowers, fungi, and tree bark. When it comes to invertebrates, their diet includes swarming insects, grasshoppers, and spiders.
In agricultural lands, southern pig-tailed macaques are known to eat crops, in a behavior referred to as “crop-raiding.” This behavior serves as an optimal, high-energy foraging strategy, allowing them to exploit nutrient-rich human-cultivated foods. As forests are cleared for agriculture or commercial development, southern pig-tailed macaques lose their preferred resources. Because crops are easier to locate and gather than wild foods, the animals are naturally compelled to consume the agricultural products. Examples of crops they eat include: African oil palms (Elaeis guineensis), corn (Zea mays L.), eggplants (Solanum melongena), chilli pepper (Capsicum annuum), tapioca (Manihot esculenta), rice (Oryza sativa), papaya (Carica papaya), and banana (Musa × paradisiaca).
Though they typically spend about 20% of their time feeding and 10% of their time foraging, while in oil palm plantations, their feeding and foraging time doubles. Macaques tend to increase crop-raiding during seasons when their preferred fruits are unavailable or when wild fruit becomes scarce. While crop-raiding, they will also eat rats on the plantations, providing beneficial pest control to the farmers who may ultimately not want them on their lands.
Behavior and Lifestyle
Southern pig-tailed macaques are diurnal, meaning they are primarily active during the day and rest at night. Throughout the day, they utilize terrestrial and arboreal environments. While 50% of their daily activity occurs on the ground, they frequently climb trees. In fact, they are very skilled climbers, and often scurry up trees for foraging, or to escape predators. Their primary natural predators include tigers (Panthera tigris), clouded leopards (Neofelis nebulosa), reticulated pythons (Malayopython reticulatus), false gharials (Tomistoma schlegelii), and large birds of prey like Philippine eagles (Pithecophaga jefferyi).
Southern pig-tailed macaques do not build structures to sleep in at night. Instead, they find secure, sheltered locations that offer protection from predators and poor weather. In the wild, they prefer mature trees for rest periods, though they also sleep on or near fallen trees with thick vegetation. In urban environments, they look for elevated and secure locations. About 20% of their day is spent resting.
Their preferred mode of movement is quadrupedalism, meaning they frequently walk and run on four limbs. Occasionally, they will travel bipedally, or on two legs, using their hindlimbs, but only over short distances. They are naturally dextrous, and in urban environments, they can easily climb man-made structures such as power lines or roofs. Their strong limbs enhance their stability, allowing them to navigate tricky surfaces and difficult terrain.
On oil palm plantations, southern pig-tailed macaques are skilled rat hunters, occasionally killing as many as 3,000 rats per year! Their predatory behavior is a natural, biological pest control tactic.
Since rats are abundant on these plantations, macaques target them as a high-protein food source that supplements their primarily vegetarian diet. While some humans may consider macaques as pests themselves, macaques actually help reduce overall crop damage by preying on rats, which pose a more significant threat to agriculture.
Southern pig-tailed macaques have a home range of about 0.232 and 3.20 square miles (0.6 and 8.28 square kilometers) and cover about 0.513 and 1.84 miles (825 and 2,964 meters) in a day. Daily travel distances change seasonally in response to food availability, temperature, and habitat quality. For example, during colder seasons with low food availability, they often travel less to conserve their energy, which is an effective low-cost strategy. The opposite typically occurs in warmer climates.
Led by an adult female, they live in multi-male, multi-female groups that consist of between 9 and 80 individuals. Larger groups often break into smaller groups of 2 to 6 individuals for the purpose of foraging, because it reduces the frequency of conflict at feeding sites. At night, the larger group reforms, and everyone comes back together. Long-tailed macaques (Macaca fascicularis) are also commonly associated with southern pig-tailed macaques in the wild, but they are usually only observed together while in coastal, mangrove, or suburban environments.
Social structure is very important for southern pig-tailed macaques, and both males and females have distinct, linear hierarchies. Linear hierarchies are social orders that feature “pecking orders.” A male’s position is determined by strength and his ability to compete, and young males must ascend from the lowest tier of hierarchy to prove themselves. Males are responsible for managing group conflict, so it is important that their respect is earned from others.
Females have inherited statuses, which means that the offspring of higher-ranking females are dominant over those of lower-ranking females. They enforce their social bonds through behaviors such as grooming, huddling, or food sharing. While males are typically physically stronger and dominant in direct contests, females utilize their social networks and bonds to compete against them. For example, it is not uncommon to see females forming alliances with each other to attack lower-ranking males over resources.
Macaques exhibit a diverse vocal repertoire, such as cooing, barking, grunting, and screaming. Different calls serve specific purposes, and vocalizations are often tied to social rank and dominance. Their vocalizations are often combined with facial expressions to form multi-modal signals, which combine two sensory types. For example, a “yawn”, or baring of teeth, from one male to another male serves as a visual warning to oncoming aggression. This is often accompanied by “kraa” sounds, fixed eye contact, and raised eyebrows.
As mentioned, macaques have long, sharp canine teeth that are utilized as a communication tool, primarily during intrasexual competition. Intrasexual competition is rivalry between members of the same sex for access to mates, resources, or status. This type of competition is most prominent in males and is used to threaten or intimidate other males. Females are more attracted to males with long canines and are likely to approach and mate with those that have significant canines. Biologically, long canines are interpreted as having good genes, which is why females are attracted to them. They want to pass those traits onto their own offspring.
Macaque grooming is another important communication skill as it maintains social structure and helps to establish alliances between group members. Macaques use their hands to remove dirt or insects from others’ fur. The act is known to relax individuals as the action has calming effects. Techniques are typically passed down from mother to offspring, so it is also common for closely related animals to groom one another. It is also frequently utilized by females in order to attract high-ranking males, and it can be traded for services relating to mating opportunities.
Southern pig-tailed macaques are polygynandrous, meaning both sexes mate with multiple partners. While dominant males often guard fertile females away from lower-ranked males, females choose their mates. When a female is ready to mate, she will present her backside to the male. With a swollen, bright backside, her fertility is very apparent. After a 6-month pregnancy, mothers give birth to one infant. The time between births is approximately two years. Newborns are covered with black fur, called a natal coat, that gradually transitions into their adult coloration. Their head retains the small, geometric black patch on top as they mature.
For the first 12 to 14 months of their lives, mothers nurse their young and eventually wean them off milk. Given their hierarchical social structure, the success of a strong mother-infant bond is extremely important. Weak bonds formed during this period can cause long-term consequences, such as heightened anxiety, chronic stress, or extreme aggression. For the infants affected, these negative behaviors can continue into adulthood, sometimes resulting in them repeating their parents’ patterns. By 1.5 years old, their diet resembles that of an adult. Once they become juveniles, between the ages of 1.5 and 3.5 years old, they are less dependent on their mothers for transportation and feeding. Until sexual maturity is reached, they spend most of their time playing with other juveniles and exploring their surroundings.
Sexual maturity is reached between the ages of 3 and 5 years old. Females remain with their troop for their entire lives, but males eventually disperse to find a new troop. Once found, he will join the troop at the bottom tier and attempt to work his way up the rankings.
As omnivorous primates, they play a crucial role as key seed dispersers, consuming a wide variety of fruits and seeds throughout their environment. When eating these products and moving them across their home range, they disperse seeds through defecation, dropping, or spitting. By transferring seeds away from their parent plants, macaques allow the plant to grow and mature in new environments. Because they travel often and thrive in many different ecosystems, their actions as seed dispersers evidently diversify their range and encourage forest regeneration. Where deforestation and habitat destruction have caused fragmentation and degradation, these behaviors are especially critical.
Since they also consume insects, invertebrates, and small vertebrates, pig-tailed macaques also act as natural pest controllers in agricultural areas. In addition to hunting rat populations, they actively forage for insects by tearing them away from tree foliage. This is particularly advantageous on oil palm plantations because it reduces the need for farmers to use chemical pesticides on their crops.
The International Union for Conservation of Nature lists southern pig-tailed macaques as Endangered (IUCN, 2022), appearing on the IUCN Red List of Threatened Species. This classification is based on a suspected population reduction of more than 50% over the course of the last 33 years.
Southern pig-tailed macaques are very sensitive to habitat disturbance and deforestation, making them an especially vulnerable species. From 2013 to 2017, Malaysia lost 11.3% of its primary forest and 16.8% of tree cover, likely due to increased mining activities and continued timber and logging production. Oil palm plantations are not suitable habitats for them, and lowland tropical rainforests are rapidly being converted to large-scale oil palm production centers. The establishment of oil palm plantations not only causes a loss of habitat biodiversity, but it also contributes to habitat fragmentation and environmental pollution through chemical fertilizers or pesticide runoffs. Because of this, macaques have experienced a 10% decline in local site occupancy in heavily disturbed and clear-cut forest sites, and infants have high mortality rates.
Crop-raiding is increasing human-wildlife conflicts for macaques. Harassment by farmers and dogs results in higher rates of injury or death, exposure to predators, and heightened stress. They are also hunted, trapped, and illegally sold as pets, for use in biomedical research, and for human consumption. Southern pig-tailed macaques have a generally negative public perception by communities living alongside them. From 2013 to 2018, the Department of Wildlife and National Parks of Peninsular Malaysia received an average of 298 complaints annually about these monkeys, largely due to crop-raiding.
Southern pig-tailed 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.
In Peninsular Malaysia, they are protected under the Wildlife Conservation Act of 2010, in Sabah under the Wildlife Conservation Enactment of 1997, and in Sarawak under the Wildlife Protection Ordinance of 1998. “Protected” indicates that hunting, keeping, or trading of that species is forbidden without a license. Hunting for food is a traditional practice amongst indigenous gatherers in Malaysia, and Schedule 6 of the Wildlife Conservation Act of 2010 provides hunters with an exception.
In Thailand, they are not specifically listed on the Wild Animal Preservation and Protection Act, B.E. 2562. Nevertheless, they are given the general protection of wildlife, which restricts hunting and capture in all protected areas and forest lands.
In 2024, the People for the Ethical Treatment of Animals (PETA) petitioned the U.S. Fish and Wildlife Service to list southern pig-tailed macaques under the U.S. Endangered Species Act (ESA) because their populations declined by at least 50% between 1989 and 2022. Their petition cited that this decline is due to habitat loss, increased trade, and the high demand and use in the United States for biomedical research. Ultimately, the petition was rejected by the U.S. Fish and Wildlife Service.
To protect this species, the effectiveness of protected areas should be assessed. Scientists from the Macaca Nemestrina Project are working to better understand the distribution, abundance, and ecological threats to the species.
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Written by Brooklynne Mitchell-Arno, January 2026