FORMOSAN ROCK MACAQUE
Geographic Distribution and Habitat
The Formosan rock macaque, also known as the Taiwan macaque, is native to the temperate forests in the mountains of Taiwan. They are the only non-human primates native to Taiwan. The species also exists in parts of Japan due to a series of both deliberate and accidental introductions that occurred in the mid-20th century.
Size, Weight, and Lifespan
Male Formosan rock macaques are noticeably larger than their female counterparts. Males measure 18 to 21 inches (45-54 cm) in length and weigh about 13 to 20 pounds (6-9 kg). By comparison, females stand at around 16 inches (40 cm) and weigh 11 pounds (5 kg) on average. Both sexes have tails that are about 16 inches (40 cm).
The lifespan of the Formosan rock macaque has not been specifically studied; however, their closest relatives have been known to live into their 30s both in captivity and in the wild.
Formosan rock macaques sport a brown coat of fur in the summer and a gray coat in the winter. They have white or gray fur covering their chests. Their faces are naked and pink with large eyes and a long, flat nose. The macaque’s jaw is built for a diverse diet, featuring four large canine teeth and several strong molars.
Formosan rock macaques are one of the 45 species of monkeys found in the subfamily Cercopithecinae. This group, consisting of macaques, baboons, and vervets, can be characterized by their cheek pouches. Monkeys with cheek pouches can quickly take large amounts of food, store them in their cheeks, and retreat to a safe place to eat without having to worry about predators or thieves. Although this adaptation did not come about with humans in mind, cheek pouches are particularly useful when hurriedly raiding human houses or trying to get as much food as possible from a tourist.
These macaques have an incredibly varied diet. Fruits make up about half of their diet. Seeds, leaves, and insects also make up significant parts of their diet. Formosan rock macaques forage from up to 300 different plants. They have also been known to raid farms and houses for foods such as sweet potatoes and peanuts.
Behavior and Lifestyle
Formosan rock macaques are diurnal, that is, active during daylight hours. They prefer to spend most of their life on the ground and, as such, are quadrupedal, meaning they walk on all four limbs.
Formosan rock macaques, introduced to Japan, have been known to interbreed with the local Japanese macaques (more commonly known as snow monkeys) creating hybrids of the two species.
Ideally, Formosan rock macaques would live in groups of as many as 100 individuals living in a multi-male/multi-female system averaging about 20 males and 25 females. However, due to pressures from human activities, most live in much smaller groups today, averaging about 10 members on average. Some of these groups only feature one male, although all-male bachelor groups will temporarily join these groups during mating season.
There is a separate hierarchy of males and females in each group. If there are multiple males in a group, one male will attempt to establish dominance over all challengers. Female dominance is established through lineage, with the daughters of the dominant females taking precedence over the more distantly related females.
While foraging, the group stays in contact with one another through “gu” calls; the others respond with a “kyaw-kyaw” call. Macaques also communicate through facial expressions. A smile with clenched teeth is a gesture of submission, while an open mouth with covered teeth indicates aggression.
Mating season for Formosan rock macaques occurs between November and January. Female macaques give birth to a single offspring every one to two years after a pregnancy of 5 to 6 months.
Both males and females reach puberty at around 5 years of age. At that time, males will leave their group and usually join a bachelor group. Meanwhile, females will stay with their natal group for life. That said, it is possible for a low-ranking female to leave her group and form a new one where she’ll enjoy a higher ranking.
Females between the ages of 5 and 9 who are sexually mature but still young and inexperienced, typically only give birth every two years, as opposed to older females who tend to give birth every year.
Due to their diverse diet, Formosan rock macaques are invaluable seed dispersers for their environment. When they digest fruits or seeds—which combined make up two-thirds of their diet—they release the seeds in another part of the forest, spreading that plants’ genes and ensuring a more diverse ecosystem.
Natural predators of the Formosan rock macaque include clouded leopards and large birds of prey.
The Formosan rock macaque is listed as Least Concern by the International Union for Conservation of Nature (IUCN, 2015) thanks to their protected habitats and early success of policies implemented by the government. However, the rise in agriculture has proven to be a threat to these macaques, not just due to the destruction of their habitats, but also because they are now being viewed as pests who raid crops. They have also been hunted for food and captured for medical research. In 1989, the government of Taiwan estimated that 3,000 macaques were killed by humans each year.
In 1989, Taiwan adopted the Wildlife Conservation Act “to conserve wildlife, protect species diversity, and maintain the balance of natural ecosystems.” The act has proven to be a great success for Formosan rock macaques, who have seen their numbers rebound and were upgraded from Vulnerable to Least Concern by the IUCN in 2008.
Written by Eric Starr, November 2018