Stump-tailed macaque

Macaca arctoides

TAXONOMY

Suborder: Haplorrhini

Infraorder: Simiiformes

Superfamily: Cercopithecoidea

Family: Cercopithecidae

Subfamily: Cercopithecinae

Genus: Macaca

Species: M. arctoides

Other names: bear macaque or stump-tailed macaque

Conservation status: Vulnerable

Life span: 30 years

Total population: Unknown

Regions: China, India, Burma, Bangladesh, Malaysia, Thailand

Gestation: about 6 months (177 days)

Height: 20.4 to 25.6 in (M), 19.1 to 23.0 in (F)

Weight: 21.8 to 22.5 lb (M), 16.5 to 20.1 lb (F)

Appearance

Aptly named after a few distinguishing characteristics, bear macaques or stump-tailed macaques have thick, long, dark brown fur covering their bodies and short tails which measure between 3.2 and 69 mm (.12 and 2.7 in). Stump-tailed macaques have bright pink or red faces which darken to brown or nearly black as they age and are exposed to sunlight. They are covered with long, shaggy fur, but their short tails and faces are hairless and they go bald with age.

Infants are born white and darken with age. Males are much larger than females, measuring between 517 and 650 mm (20.4 to 25.6 in) and weighing between 9.9 and 10.2 kg (21.8 and 22.5 lb). Females have an average height between 485 and 585 mm (19.1 and 23.0 in) and weigh between 7.5 and 9.1 kg (16.5 and 20.1 lb).

This sexual dimorphism extends to more than just body size; male stump-tailed macaques have elongated canine teeth compared to females, which are important for establishing dominance within social groups.

All macaques, including stumptails, have pouches in their cheeks to store food for short periods of time. They travel quadrupedally and usually on the ground for they are not very agile in trees. They are not known to swim, as do other species of macaques (Macaca).

RANGE

Stump-tailed macaques are distributed from northeastern India and southern China into the northwestern tip of West Malaysia on the Malay Peninsula. They are also found in Burma, Thailand, Vietnam, and far eastern Bangladesh. A study population was introduced to Tanaxpillo, an uninhabited island in Lake Catemaco, Veracruz, Mexico in 1974, where they range in semi-natural conditions.

There have been very few long-term studies of stump-tailed macaques in the wild and most information comes from the introduced population on Tanaxpillo or other captive settings.

HABITAT

In general, stump-tailed macaques are found in subtropical and tropical broadleaf evergreen forest. Found in different habitats at different elevations, they live in dense evergreen rainforests below 1500 m (4921 ft) and subtropical evergreen forest between 1800 and 2500 m (5905 and 8202 ft), depending on the amount of rainfall in the area.

They depend on rainforests for food and shelter and are not found in dry forests except where they range in the Himalayan region of India. They do not spend much time in secondary forests and only do so if they are bordering primary tropical forest.

The tropical flora on Tanaxpillo consists of evergreen trees, vines, shrubs, grasses, cacti and water plants and the stump-tailed macaques coexist with iguanas, lizards, frogs, snakes, mice, birds and insects, some of which are native to Mexico.

ECOLOGY

Starting the day at dawn, stump-tailed macaques spend the early morning, until midday, traveling and feeding. They are frugivore-omnivores and a significant part of their diet is devoted to fruits. They also eat seeds, flowers, leaves, roots, freshwater crabs, frogs, birds, bird eggs, and insects.

They also raid crops prefering corn and other cultivated fruits. During the middle of the day, the group stops traveling and rests in the shade, spending time on social activities such as grooming while juveniles and adolescents play. In the late afternoon foraging begins again as they travel to their sleeping site, usually large trees or cliffs.

The daily range of stump-tailed macaques is between two and three kilometers (1.24 to 1.86 mi), but they do not have to travel as far during the rainy season when food is more abundant. Home range is unknown but thought to be several square kilometers. Though they spend the majority of the day traveling on the ground, usually along the banks of rivers and streams, stump-tailed macaques also forage for fruit and leaves in trees and flee to trees when in danger.

In Mexico, stump-tailed macaques readily experiment with new foods, including native Mexican plants that would obviously not be encountered anywhere in their natural range in Asia. The Mexican stumptails hunt spiders, worms, snails, insects, frogs, lizards, birds and field mice and also search out turtle and bird eggs. Their diet is also supplemented by researchers in the form of a prefabricated pellet diet as well as assorted fruits and vegetables.

Potential predators of stump-tailed macaques include clouded leopards, leopards, dogs, and large raptors. When predatory animals are near, they respond by assuming threatening postures, shaking trees and branches, and baring their canine teeth in threat. No predation event has been recorded.

SPECIAL NOTES

Like some human males, stumptail macaques become partially bald as they age. This process of balding is similar to male-pattern baldness seen in humans because hair loss starts at the forehead and advances toward the back of the skull over time, but unlike humans, this pattern is seen in both male and female stumptails.

Researchers have studied balding in stumptail macaques and have developed treatments for baldness, namely minoxidil, or as it is commercially marketed, Rogaine. Minoxidil was originally developed as a drug to treat high blood pressure, but one of the side effects identified was excessive hair growth. Testing of the drug on stumptail macaques revealed hair regrowth and maintenance of newly regrown areas on balding scalps. By first testing its efficacy and safeness on nonhuman primates, researchers were able to develop the drug for human use.