Macaca cyclopis

Geographic Distribution and Habitat

Formosan rock macaques, also known as Taiwan or Taiwanese macaques, are endemic to the island of Taiwan in eastern Asia. The first descriptions of this species from the 19th century reported a wider distribution than today. Once upon a time, these macaques were found along the island’s coasts, but a surge in human activity has since driven them into its more mountainous regions inland. Broadleaf evergreen forests are their preferred habitat, but populations of this adaptable species are also found in less desirable habitats, including mixed broadleaf-coniferous, coniferous, and bamboo forests. Some even survive quite happily in secondary-growth forests and small remnant forest patches.


Though endemic to Taiwan, some Formosan rock macaques have found themselves living in Japan, introduced by humans sometime in the last century. In some regions, they have hybridized with Japanese macaques (Macaca fuscata), also known as snow macaques, one of Formosan macaques’ closest living relatives. Molecular studies suggest these two species diverged some 380,000 to 440,000 years ago.

Formosan macaque geographic range. Map: IUCN, 2020

Size, Weight, and Lifespan

Formosan rock macaque males are generally larger than females. The average male weighs in at 22 pounds (10 kg) while the average female is only about 15 pounds (6.69 kg). Head and torso combined, males measure an average of 21 inches (54 cm) and females 19 inches (48 cm). But there is some overlap in size, with the largest females measuring 23 inches (58.5 cm). Tails are generally just a little bit shorter than their bodies.

The average lifespan of Formosan macaques is assumed to be similar to those of other macaque species, which is less than 30 years in the wild.


Formosan rock macaques have a distinctly “macaque” look. Their small bodies pack some muscle, especially those of males. Their tails are long and expressive, protruding prominently from their backends.

In a relaxed state, Formosan rock macaques can appear quite stately and dignified. Light red faces gaze out through tufted frames of fur that partly hide their ears. The skin on their abdomens has a subtle blue tint. Long, strong fingers protrude hairless and black from their long palms.

Compared to their snow macaque cousins—residents of Japan’s colder climates—Formosan rock macaques grow less fluffy fur that is more suitable for the tropical and subtropical regions of Taiwan. The color of their fur also changes seasonally, appearing dark gray in winter and turning a lighter, olive hue by summer.


Formosan macaques enjoy a smorgasbord of different foods. Fruits, berries, seeds, leaves, shoots, flowers, nectar, lichens, and even bark from the vegetarian staples of their diet, providing them with the vitamins and minerals needed to stay happy and healthy. Proteins and other nutrients come more reliably from munching on the insects and other small invertebrates they find. Larvae are a particular delicacy.

Formosan rock macaques have also been known to chow down on small amphibians, reptiles, and even birds. Reports from the 19th century, when macaque troops still lived along the coast, describe them eating mollusks and crustaceans.

The macaque troops in Shoushan show a strong preference for the fruit of Naves ehretia, which are small berry-like fruits said to taste like persimmons.

Behavior and Lifestyle

Formosan rock macaques are semi-terrestrial, spending their waking hours both in trees and on the ground. They are agile creatures adept at climbing and leaping, but most of the time they run on all fours. Reports from the 19th century describe these macaques darting around on inaccessible rocks and cliffs along Taiwan’s seacoasts. Today, they keep to the island’s hilly and mountainous forest and plains regions inland.

Macaques are well known for their adaptability and their go-getter attitudes. Indeed, Formosan rock macaques are not shy monkeys, and when it comes to dealing with humans, they are willing to push boundaries. To the frustration of locals, they regularly raid crops, digging up tasty sweet potatoes and peanuts and sometimes even entering people’s homes just to see what they can find. Obviously, this sort of behavior rarely bodes well for the monkeys.

Today—in part due to a controversial history of food provisioning the monkeys—many troops of Formosan rock macaques are accustomed to the presence of humans, routinely interacting with hikers and tourists. A lack of understanding on the part of the humans, however, can sometimes lead these (mostly) innocent interactions to take an unfriendly turn. Many macaques have learned to associate humans with delicious food, which they will go to great lengths to acquire. This creates tension that sometimes escalates to physical violence if their human targets are not careful.

Macaques tend to be food motivated, and some of the most interesting behaviors observed in Formosan rock macaques have to do with how they go about acquiring it. For instance, they carefully remove the unpalatable bristles from otherwise scrumptious caterpillars before plopping their meaty bodies in their mouths. Other times, they handle the caterpillars with a leaf, placing it on their palm and using it to rub the bristles off. Certain delicious insect larvae weave cocoons on the underside of leaves, but the material used to make the cocoons causes itching when contacted. To extract them, Formosan rock macaques have figured out how to roll the cocoon up inside the leaf so they can safely squeeze the tasty larvae out.

In one particularly noteworthy observation, a group of macaques found a hollowed-out log where a frog had laid its eggs. The eggs had hatched into tadpoles. The macaques ran their hands through the water, pushing the tadpoles to one end where they could more easily scoop up and eat them.

Washing food before consumption is also a popular ritual among this species.

Fun Facts

Besides humans, Formosan rock macaques are the only primates found in Taiwan.

A drop in sea level and glacial advances around 300,000 years ago is theorized to have allowed Formosan rock macaques’ original ancestors to access the island.

Daily Life and Group Dynamics

Formosan rock macaques live in multimale-multifemale groups with generally fewer males than females. Long ago, large groups of up to 100 members were reported. Today, due to human activities, the average group has only 45 members. With their habitats dwindling and fragmented, many groups have come to more closely resemble uni-male systems with only two to ten members, the majority of whom are females and their offspring.

Typical of macaque species, Formosan rock macaque society functions according to strict hierarchies. While males are generally dominant to females, both sexes navigate their own separate hierarchies within the group. Dominance among females is established by birth while males vie for dominance with other males, trying to intimidate and fight their way up the social ladder. Males sometimes form coalitions in order to supplant a group’s dominant male. Access to food is at the center of both hierarchies, but mating is also an important factor for males.

Formosan rock macaques are generally territorial and protective of their groups; outsiders are not warmly welcomed. However, separate groups have sometimes been observed to share sleeping sites and to keep ranges that overlap significantly.

A group of Formosan rock macaques wakes together in the early morning. They begin their day with some social time, reestablishing their bonds after a long night’s sleep. They then set out to find food. On average, they spend roughly a quarter of their day traveling to their various foraging spots. Almost 50% of their waking hours are spent foraging. Between meals, they lay back and relax a bit. After digesting a little, they socialize. Adults take turns grooming each other and the children play. At dusk, the group settles down for the night, finding a tall tree or cliff to cozy up in where they are safe from predators.

In today’s Taiwan, with its heavily fragmented habitats, few Formosan rock macaque groups are able to avoid daily contact with humans. The macaques generally associate humans with food, and may even actively seek them out, approaching or harassing them to get it. Locals are not necessarily more likely to know how to deal with the monkeys’ antics than tourists, and it is not uncommon that human-macaque interactions grow tense or even occasionally violent.


Primates are social, and social creatures communicate. Formosan rock macaques use a variety of methods to share information with each other. Grooming and playing are tactile ways of growing and cementing the social bonds that make living in a social group pleasant and desirable.

For Formosan rock macaques, facial expressions, hand gestures, and other forms of body language send important cues to others about how an individual is feeling. A grimace, for instance, in which the lips are retracted and teeth clenched, communicates fear or aversion, while an open mouth with teeth covered shows aggression. Humans, with their own body signals, can easily misread those of macaques they come in contact with, which is often what drives agonistic interactions between the two primates.

Formosan rock macaques make a variety of vocalizations that can be used to communicate all kinds of information. The most basic of these are contact coos. To help keep track of everybody, everyone in the group regularly makes a special cooing sound. When young ones find themselves alone, they make a different type of coo that urges adults to come to their rescue. Another sort of coo is made when groups find themselves in agonistic encounters with outsiders. And, when group members find themselves completely lost, they emit another, very loud coo.

Greetings are also important in Formosan rock macaque society. A common greeting is used by everyone in the group to initiate contact. Other greetings are also used, which depend on individuals’ hierarchical relationship to another.

Infants and juveniles use a complex repertoire of sounds in order to communicate with their parents, including growls, rattles, roars, squeaks, squawks, and whines. A clucking sound signals that a young one is alone while a special vocalization known as a “gecker” is used when an infant feels ignored by its mother. Infants also make weeping sounds to get attention and babble during times of independent exploration.

It has been noted by researchers that the vocalizations Formosan rock macaques use most frequently are shorter than those they use more rarely. This phenomenon (known in linguistics as “the law of brevity”) is a feature their communication methods have in common with human vocalizations and language.

Reproduction and Family

Like other macaques, Formosan rock macaques are polygynous. This means they mate with many different partners. Mating isn’t just a free-for-all, however; a macaque’s place in the hierarchy determines with whom they can and can’t mate. Dominant males, for instance, typically monopolize any female in estrus, helping to ensure she bears his offspring. However, females may mate with up to five partners in a single day.

A female in estrus develops a swelling at her rear. She initiates copulation by presenting her swelling to a desirable male. The male then mounts and inseminates her. Mating peaks in the dry season, between September and February; most births occur during the wet season, between April and June.

Her pregnancy lasts an average of 162 days or about 5 months. Her newborn stays in close contact, clinging to her fur for the better part of a year. Though other females may offer occasional help, she alone remains his primary caretaker, nursing, grooming, and protecting him.

At the age of one, young macaques begin to gain a little independence. Over the next several years, they make further and further explorations of their environment, they begin playing with peers, and they practice the skills needed to make it in Formosan macaque society. At four years old, they enter a new subadult phase. During this phase, they continue to master their skills in the comfort of their natal group before leaving it forever.

When striking out on their own, males typically join temporary bachelor groups, which offer them protection and social bonds while they wait to join a new group. Sometimes members of these bachelor groups collaborate in order to supplant the dominant male of a group they wish to take over.

Females may also choose to leave their natal group when they reach adulthood, but it’s more common that they remain. On average, a female is four or five years of age when she has her first birth, and she usually becomes pregnant again around the same time her latest offspring is weaned.

Ecological Role

Formosan rock macaques play important ecological roles in local food chains and, as fruit eaters, help to disperse seeds. When macaques consume fruit, the seeds pass through their digestive tracts and drop to the forest floor in their feces, often far from where it was ingested.

Formosan rock macaques are occasionally hunted by large birds of prey, but cloud leopards are by far their most significant natural predator.

Conservation Status and Threats

The Formosan rock macaque is classified as Least Concern by the International Union for Conservation of Nature (IUCN, 2015), appearing on the IUCN Red List of Threatened Species. At the moment, populations are stable—possibly even climbing.

This classification, however, may only represent the big-picture situation while glossing over more particular local trends. After all, habitat loss and fragmentation are more problematic in some regions than in others. Agricultural development and other human activities have already driven this species from the coastal areas where it was once prevalent. Furthermore, logging interests have increased and continue to degrade Taiwan’s once vibrant forests.

While this species has proved itself adaptable, the resulting forest fragmentation will gradually create genetic bottlenecks, a condition in which a species’ population is reduced in size (i.e., by a cataclysmic event, habitat fragmentation, etc.) limiting the genetic diversity of the species. When gene flow slows or halts, primates become more vulnerable to disease, parasites, and birth defects. This trend intensifies generation by generation until so few individuals are viable that procreation itself comes to a screeching halt.

A significant factor for Formosan rock macaques’ conservation is their proximity to humans. Some groups have become so accustomed to human presence that it’s almost second nature to seek them out in the hopes of acquiring free food. In some instances, macaques have even grown reliant on handouts. Proximity also puts both macaques and humans at risk of contracting zoonotic diseases, not to mention interactions between the two species are not always peaceful.

The current classification of this species is also representative of an era in which Formosan rock macaques enjoyed protective status in Taiwan. But, in 2019, the country’s Forestry Bureau downgraded the species’ status from “protected species” to “general wildlife”—arguing that their numbers were stable and their habitats well managed. Since the downgrade, farmers frustrated by crop-raiding macaque troops have killed the monkeys with impunity, and the number of macaques kept in captivity as pets have risen significantly. Reports catalog a host of cruel and unusual treatment of captive macaques. Captors chain them along hiking trails for the entertainment of tourists or abuse them in other ways. One man deprived his macaque prisoner of water, convinced that it would keep the macaque from getting too big.

Advocates for the macaques originally warned that downgrading their protections would lead to these trends. They have also accused the Forestry Bureau of caving to the demands of farmers who consider them pests. The lift of protections has caused a great deal of confusion among the general population. This highlights the need for more education about the importance of coexisting peacefully with Taiwan’s special macaques.

Conservation Efforts

The Formosan rock 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.

In Taiwan, this species was once listed as a “protected species” under the country’s Wildlife Conservation Law, an act that helped their populations to stabilize. Since being downgraded to “general wildlife” in 2019, however, problems with killing and capturing Formosan rock macaques appear to have increased drastically. We won’t know how bad the situation really is until more research has been conducted, but advocates say it is safe to assume that the trend is worse than it appears outright. The fallout of lifting these protections is a prime example of how important it is to maintain these laws. Stable populations shouldn’t justify the loss of protections for a rare and valuable species whose well-being (not to mention their very existence) hangs in the balance.

In reaction to the situation following the 2019 downgrade, local advocates have created hotlines to call and report any macaque-related incidents that may require intervention. While working tirelessly to have the original protections reinstated, they have already been successful at passing legislation to ban the ownership and trade of macaques in Taiwan, effective as of September 2022. Now, anyone keeping a macaque in captivity without proper registration will be heavily fined.

Luckily, Formosan rock macaques reside in several protected places including five national parks, twelve nature reserves, and eleven major wildlife habitats and refuges, which all provide adequate space and habitat. Still, the steep rise in keeping macaques as pets since the 2019 downgrade suggests that keeping on top of enforcement is paramount for the well-being of this species.

The Association for Coexistence with Macaca cyclopis (ACMC) is an important advocate in Taiwan for Formosan rock macaques. Run by Lin Mei Yin, this 20-year-old organization works to end prejudice against the macaques through education. They visit schools and run a Youtube channel, spreading a message that stresses that macaques are not pets and should not be killed for any reason. They also lead educational hikes in Shoushan to visit the macaques that live along one of Taiwan’s most popular hiking trails. This encounter gives students first-hand experiences of the macaques in a guided setting in which they learn strategies to peacefully coexist with them. Since its founding, Lin has conducted hundreds of speeches and has led over 700 guided tours, altogether influencing over 10,000 people. Hers was perhaps the loudest voice opposed to the downgrade of Formosan rock macaques’ protective status in 2019, and she continues to work to reverse the legislation.


Written by Zachary Lussier, January 2023