TIBETAN MACAQUE

Macaca thibetana

Geographic Distribution and Habitat

The Tibetan macaque (Macaca thibetana), also commonly known as the Chinese stump-tailed macaque, Pere David’s macaque, Milne-Edwards’ macaque, or red-faced monkey, is an Afro-Eurasian monkey that lives in the Eastern regions of Tibet, east to the province of Guangdong and north to Shaanxi province in China. A few populations have also been spotted in the northeast part of India.

Living in subtropical evergreen and leaf-shedding trees forests and in low woods and bushy areas, these exceptionally large macaques live at elevations of 980 to 6,900 feet (300 to 2,100 m), although they can often be found at higher elevations, in rocky terrains. The climate in these regions is usually mild in the winter and hot and humid in the summer; however, because they live at such elevations, they enjoy milder climate in the summer but must withstand freezing temperatures in the winter, to which they are promptly adapted.

TAXONOMIC NOTES

Four subspecies of Tibetan macaque are officially recognized:

  • The Tibetan macaque, Macaca thibetana thibetana, found in northern and western Sichuan and southwestern Shaanxi;
  • The Macaca thibetana pullus, which lives in northern and eastern Fujian, eastern Jiangxi, southern Zhejiang, northern Guangdong, and Zhangjiajie in Hunan;
  • The Guizhou macaque, Macaca thibetana guizhouensis, found in southern and eastern Guizhou, northeastern Yunnan, and western Hunan;
  • The Huangshan macaque, Macaca thibetana huangshanensis, which inhabits southern Anhui in eastern China.
Tibetan macaque range, IUCN 2024

Size, Weight, and Lifespan

The Tibetan macaque is the largest macaque in existence. Males measure a whopping 24–28 inches (61–71 cm) on average, while females are typically 19–25 inches (49–63 cm) long. The size difference between males and females also brings about a substantial weight disparity. In fact, adult males can weigh up to 40 pounds (18.3 kg), whereas adult females are lighter, weighing around 28 pounds (12.8 kg). Subadult males weigh approximately 28 pounds (12.7 kg), subadult females around 17.6 pounds (8 kg), juveniles about 10.5 pounds (4.75 kg), and infants approximately 5.5 pounds (2.5 kg). They live a relatively long life: they can live up to 30 years.

Appearance

Thick brown fur covers these monkeys, protecting them from the harsh climate conditions of their habitat. Their fur is dark chocolate brown over their head, back, arms, and legs, sometimes verging on a charcoal, almost black, color. In contrast, their faces are brightened by light blond hair that matches their bellies. Most females have red skin around their small, round, brown-yellow eyes. Similarly colored skin makes their muzzles stand out. Males, on the other hand, have pink or brownish skin around their eyes and muzzle. Their noses lie flat on their hairless muzzles. Male Tibetan macaques between ten and fifteen years have darker brown fur, more facial hair, and are larger. In contrast, Tibetan macaque babies have lighter-colored fur that changes around the age of two.

The Tibetan macaque has a stocky build, with strong limbs. Both sexes have very short tails, between 2 to 3 inches (7.5 cm) long, which is why they are commonly known as the Chinese stump-tailed macaque.

Diet

Due to their sheer size and life in a frigid environment, Tibetan macaques have adapted to have complex foraging strategies. Tibetan macaques eat over a hundred plant species and show incredible seasonal and local adaptability; for example, macaques that live at higher altitudes have different feeding habits than those that inhabit lower places.

More than 50% of Tibetan macaques’ diet comprises fruit. They also feed on mature leaves, bamboo shoots, young leaves, flowers, stems, and tender shoots. Occasionally, they will even eat insects or bark, when food is particularly scarce. Their dietary preferences follow seasonal patterns: their diet is the richest in summer due to the higher variation of good-quality food available. In winter, they rely on the fatty seeds and starchy nuts of the Masson pine nut and the Eyrei’s chestnut tree, respectively. These are overall less nutritious but essential to survive the cold winters of the mountains they populate.

Hidden under their furry faces, Tibetan macaques are equipped with large cheek pouches that come in very handy when foraging, as they can be used to store extra food.

Behavior and Lifestyle

Tibetan macaques are diurnal creatures, meaning that they are mainly active during the daytime. They are most active in mid-morning and early afternoon, while in many regions they tend to enjoy a siesta at noon in the warm summer months. For example, in the Huangshan mountains, which are mostly rocky terrains, the sun scorches the rocks making them unbearable to the touch. During the hottest hours, the Tibetan macaques, who are mostly ground-dwelling primates, will seek refuge in shaded areas. These include tree trunks, roots, caves, and other cooler areas. In contrast, they act the complete opposite in the winter. When it’s sunny but cold, they will spend several hours soaking up the sun on exposed rocks. Conversely, they will also retreat into caves when it’s particularly stormy and snowy.

It is often in caves that they sleep at night. Other sleeping sites include trees, shrubs, and hillsides. What’s interesting is that they show an inclination for sleeping in proximity to their feeding sites. It’s not surprising given that Tibetan macaques spend about 29% of their time foraging; thus, sleeping near feeding sites and safeguarding them guarantees fewer intruders wandering about.

Tibetan macaques’ day includes a lot of sleeping as they rest for almost 32% of their day. They also move around their home range quite a lot (almost 27% of their time is spent moving), and they groom themselves and each other a great deal (7% of their day). Males spend more time resting compared to females, who instead move and groom significantly more. Juveniles, naturally, play a lot more than adults.

Tibetan macaques have virtually no natural predators since the large cats that used to live in these regions have been eradicated. They are, furthermore, quite aggressive and belligerent so they can defend themselves pretty well. Intraspecies aggression is quite common, especially among males, and given their impressive size and sheer strength, their fights often end in death.

Daily Life and Group Dynamics

Tibetan macaques live in male-dominated groups where an alpha male rules over younger male subordinates—often his offspring—and several females. However, their reign is short-lived: on average, it lasts for 10 months.

Group size varies a lot, but most groups consist of around fifty individuals. They live in relatively fluid social groups: the size and composition of their groups change depending on the various necessities of the troop. For example, Tibetan macaques tend to split into smaller groups when food is particularly scarce and move to other locations in search of better opportunities; when the troop becomes too large, Tibetan macaques part ways and form other groups. It is often lower-ranking members that split from the original group to move elsewhere.

Tibetan macaques live in groups that include multiple males and females. However, when juvenile males reach sexual maturity, around the age of 7, they leave their birth group. They either form a new group or challenge dominant males in neighboring groups to possibly become the leader. These challenges can be very violent and often result in severe injuries and even death. Unlike males, female Tibetan macaques generally remain with their birth group for life. Females also follow a hierarchical structure, led by a dominant female and several subordinates. However, because they tend to stay with their natal group, females are often blood-related and form very intimate relationships due to their familiarity with each other. They groom one another much more often because of this, and they even form cliques — that is, they gather with certain members more frequently than with others.

Their home range is quite impressive: it extends over 5.4 square miles (14.13 km²). They live in close proximity to another species of macaque, the rhesus macaque, Macaca mulatta. Nevertheless, their interactions are limited because they inhabit different areas of the same environment, considering that Tibetan macaques live at much higher altitudes. In some regions, they interact with other species, such as the golden snub-nosed monkey, Rhinopithecus roxellana, to form mutualistic relationships.

Communication

The Tibetan macaque is a highly vocal species that uses around twelve distinct calls. Their calls can be grouped into two categories: clear calls and harsh calls.

Five different calls are clear calls, and they owe their name to the fact that they are clearly organized and musical. In this group, we have coos, squawks, leap coos, weeping calls, and modulated tonal screams.

Tibetan macaques use so-called coo sounds during foraging and group movements. They are short, harmonic calls, probably used to reinforce group cohesion.

Leap coos are clear and tonal. They get their moniker from the fact that when heard, one can clearly spot a “leap” in frequency toward the end of the call. Adults use them when foraging, during group movements, and even in response to the presence of tourists. Juveniles, on the other hand, also use them during weaning.

Squawks are similar to coos, but they are plosive calls and are placed on top of a loud, messier background with lots of higher-pitched sounds. These are emitted by males during mating. Females also emit calls during mating, but unlike males, they’re quieter and much shorter in duration. These calls are not well understood but are often referred to as female copulation calls.

Weeping calls are also uttered by juveniles. Similarly to leap coos, they are uttered after being rejected or avoided by mothers who have started weaning their offspring.

Modulated tonal screams are uttered by subordinate males and females when threatened or attacked. They are not used by dominant males. They are clear and tonal, with separate and noticeable changes in their pitch and tone.

Harsh calls are instead atonal and jumbled up, meaning that they are often superimposed onto messier sounds.

Squeals, noisy screams, growls, compound squeaks, pants, and the previously mentioned female copulation calls are all harsh calls.

Squeals are uttered by submissive members during intra-group aggression. Squeals are usually made of different frequencies combined.

Noisy screams are used in different situations, for example, during in-group aggression, foraging, or when the group is separated. As the name suggests, they resemble screams as they are harsh, atonal, and can be either very short, almost explosive, or incredibly long.

Growls are calls that Tibetan macaques use during aggression, dominance displays, and, surprisingly, while waiting for food. Barks are also emitted during aggression, but they’re mostly emitted by higher-ranking individuals attacked or threatened by lower-ranking ones. They’re often heard at the end of other aggressive calls.

Compound squeaks are mixed or compound explosive sounds, often emitted during serious aggression. Young Tibetan macaques also use them while being weaned.

Pants are very quiet, breathy calls, used during harassment and aggression within the group.

As an incredibly despotic species, it is no surprise that many of these calls are used during agonistic encounters—uttered in response to threats and violence or as a way to deter aggressors. However, many of these calls are also employed during foraging and traveling. Females, in particular, are much more likely to call other group members when searching for food. Nevertheless, even female Tibetan macaques tend to be of a tyrannous nature compared to some other macaque species.

Besides vocal communication, visual cues play an important role in the lives of Tibetan macaques. For example, approximately 39% of decision-making regarding group movement is accompanied by visual signals such as glances and pauses. In other words, visual cues are often used to “recruit” individuals and coordinate movement from one place to another.

Finally, physical contact, such as grooming, embracing, and genital touching—in males in particular—plays a significant role in friendly and peaceful interactions. Higher-ranking females are particularly sought after when it comes to grooming; they’re often followed by lower-ranking females in a fan-like fashion. Tibetan macaques spend up to 20% of their day grooming each other.

Reproduction and Family

Tibetan macaques are seasonal breeders. Although they mate all year round, they mainly reproduce between July and December, with births peaking around January and April. Males reach puberty around the age of 6 or 7, which is when they leave their group; females, on the other hand, reach sexual maturity by the age of 5. Interestingly, female Tibetan macaques don’t show any initiative when it comes to mating: it is rather the male who will approach the female and try to have sexual intercourse. During the mating season, high-ranking males court sexually ready females by following them, feeding with them, and resting with them for as long as two weeks. Opportunistic low-ranking males often mate with females during this time. Tibetan macaques usually give birth to a single baby, although twin births happen. They are weaned around 12 months old.

Tibetan macaques are very interested in their babies. Sometimes unrelated adults will pick an infant and bring it to another to do what’s known as bridging, an absolutely fascinating and mind-blowing behavior among Tibetan macaques: an infant is held by two macaques, usually by his or her limbs, to form what looks like a bridge. It only lasts for a few seconds because immediately after, the two macaques will start grooming each other and completely ignore the baby. In this scenario, the baby is an instrument used to facilitate positive social interactions. All social ranks and both sexes form bridges; even young adolescent Tibetan macaques do occasionally. Nevertheless, besides the novelty use of infants, babies are raised solely by their mothers.

Ecological Role

As herbivores gluttonous of fruit, Tibetan macaques contribute to spreading plant seeds in their home range. They live at such high altitudes where few other species can be found; thus, their role in maintaining a balance in these areas is of vital importance.

Conservation Status and Threats

The Tibetan macaque is classified as Near Threatened by the International Union for Conservation of Nature (IUCN, 2015), appearing on the IUCN Red List of Threatened Species. Significant habitat loss has been threatening the species for the last 30 years. Fortunately, deforestation has been decreasing, stabilizing their status.

Agriculture, logging, and housing are leading threats to the species’ survival. Trapping and hunting, with locals consuming their meat, is also a serious concern. Tourists also pose a serious threat. Human disturbance may be one of the reasons why Tibetan macaques are much more hostile towards one another. Indeed, the aggressive behavior of Tibetan macaques increases significantly with the presence of humans.

Conservation Efforts

Tibetan 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.

These creatures live in protected areas such as the natural preserves in the Sichuan province of China (Wolong, Tangihe, and Heizhugou), and the Valley of Wild Monkeys at Huangshan. Education remains the most important tool to combat habitat destruction and avoid worsening the conditions of these animals.

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Written by Mirko Cerrone, September 2024