Stump-tailed Macaque (Macaca arctoides)

Physical characteristics

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) (Fa 1989). 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 (Fa 1989; Rowe 1996; Groves 2001). 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) (Fa 1989). 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 Stump tails, have pouches in their cheeks to store food for short periods of time (Rowe 1996). They travel quadrupedally and usually on the ground for they are not very agile in trees (Rowe 1996; Srivastava 1999). They are not known to swim, as do other species of Macaques (Macaca) (Fooden 1990).


Habitat and Distribution

This Old World Monkey travels quadrupedally, usually on the ground, as it is not very agile in trees. It is generally found in subtropical and tropical broadleaf evergreen forests, in different elevations depending on the amount of rainfall in the area. It depends on rainforests for food and shelter, and is not found in dry forests except where it ranges in the Himalayan region of India, only spending time in secondary forests if it is bordering primary tropical forests. It is distributed from north-eastern India and southern China into the northwest tip of West Malaysia on the Malay Peninsula. It is 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 it ranges in semi natural conditions. Most information on the species comes from the introduced population on Tanaxpillo and other captive settings, as few long-term studies have been conducted on the stump-tailed macaque in the wild.

Ecology

Starting the day at dawn, Stump-Tailed Macaques spend the early morning, until midday, travelling 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 (Fooden 1990; Rowe 1996; Srivastava 1999). They also raid crops preferring corn and other cultivated fruits. During the middle of the day, the group stops travelling and rests in the shade, spending time on social activities such as grooming while juveniles and adolescents play (Fooden et al. 1985). 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 kilometres (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 kilometres (Srivastava 1999). Though they spend the majority of the day travelling 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 (Fooden 1990).  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 (Srivastava 1999; Cherty et al. 2002-2003). Like some human males, Stump Tail 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 Stump Tails (Uno et al. 1967). Researchers have studied balding in Stump Tail Macaques and have developed treatments for baldness, namely minoxidil, or as it is commercially marketed, Rogaine (Uno 1986). 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 Stump Tail Macaques revealed hair regrowth and maintenance of newly regrown areas on balding scalps (Uno 1986). By first testing its efficacy and safeness on non human primates, researchers were able to develop the drug for human use.

Reproduction

Stump-Tailed Macaques have low reproductive rates compared to other Macaque species. Females reach sexual maturity around four years of age and have an ovarian cycle lasting 30 days. Most mating occurs in October and November in the wild, during February and March in Mexico, and is not seasonal in captivity (Brereton 1994). Females begin to produce offspring between 4.5 and five years of age and will reproduce until about 17 years of age (Fooden 1990). Males reach sexual maturity around four years of age as well, but do not reach adult size until around six years.  Frequency of mating correlates with dominance rank among Stump-Tailed Macaques. The highest-ranking males monopolize receptive females while the highest-ranking females are also the most likely to do the most mating (Brereton 1994). Lower-ranking male Stump-Tailed Macaques use alternative methods to gain mating opportunities. One way they do this is by lagging behind with a reproductively active female as the group travels. When the dominant males are out of sight, the lower-ranking male mates with the female and the couple then moves to rejoin the group (Brereton 1992). Both males and females solicit mating, females by presenting their rumps to males and maintaining eye contact over one of their shoulders, and males by approaching a female, sitting next to her, and giving a "teeth chattering with grimace" display (Brereton 1994). During copulation, other members of the group harass the pair (Srivastava 1999). Gestation lasts 177 days and females give birth about every two years in the wild (Fooden 1990; Srivastava 1999).


Parental care

Macaque mothers are the primary caregivers for their offspring, though all of the females in the group direct attention to infants and will approach, play with, carry, groom and protect them, especially if they are born to a high-ranking mother. By protecting a high-ranking female's infant, a lower-ranking female may expect rewards of tolerance and reduced aggression by the high-ranking female (Estrada & Estrada 1984). High-ranking adult males also direct some attention towards and give protection to infants within the group. This may be because higher-ranking males have more chances to mate with females and because there is increased likelihood that infants in the group are their offspring, males have some interest in protecting them from danger (Bauers & Hearn 1994). Stump-Tailed Macaques are considered permissive mothers compared to other species, and early on they allow the infant to independently explore the surrounding environment (Maestripieri 1995). They may be this lenient because other group members are interested in infants but never treat them roughly or "kidnap" them as is seen in other macaques (e.g., M. nemestrina and M. fascicularis) (Bauers & Hearn 1994). Stump-Tailed Macaque infants are dependent for the first nine months of life, after which they are weaned, and become increasingly independence until adolescence, at 18 months (Srivastava 1999).

Communication

Communication between Stump-Tailed Macaques largely takes the form of vocal or gestural signals. Frequently seen gestures or postures are used to reinforce the dominance hierarchy and reconcile after aggressive interactions. "Hindquarter presentation" is the most common gesture seen among Stump-Tailed Macaques and is displayed by subordinates to appease dominants. Other submissive signals include "bared-teeth," "lip-smack," "teeth-chatter," and "present-arm," in which one arm is put directly in front of the face of the dominant individual to be bitten (Maestripieri 1996).

Vocal communication is also important among Stump-Tailed Macaques. The most common vocalization is the "coo" heard in a variety of contexts, but especially relevant as group members maintain contact with each other while foraging and when approaching one another to initiate friendly interactions such as grooming or huddling (Rowe 1996). "Basic grunts" are another ubiquitous signal among stump-tailed macaques; they are commonly heard between animals who are greeting one another, after aggressive interactions and when one animal is interested in another (Bauers 1989). Alpha males use a "roar" when displaying against predators or threats. Infants use "trilled-whistles" as a signal of distress to their mothers when they are out of visual contact with them or if they need to be retrieved because they cannot descend a structure that they have climbed (Bauers 1989; Maestripieri 1995).

Conservation status

Habitat disturbances affecting this species' survival include selective logging, timber and firewood collection for charcoal, building roads, dams, power lines and fisheries, deliberately set fires, fragmentation, and soil loss/erosion. These animals are hunted and traded for food, sport and traditional “medicine,” and accidental mortality due to trapping occurs. There is a local trade for bones, meat for food and the live animals as pets (Molur et al. 2003). 

In India much of its habitat is affected by Jhum cultivation (shifting or slash-and-burn) (Srivastava and Mohnot 2001). It has also been indiscriminately hunted to the brink of extinction over almost its entire distribution in this country (Srivastava and Mohnot 2001).

In Vietnam, this species is heavily targeted for use in traditional “medicine,” both in country and for trade with China. Within Lao PDR, Vietnam and Cambodia, hunting levels for food is also very high. Habitat loss is a relatively lower threat compared to hunting (R. Timmins pers. comm.).

In Myanmar, logging and timber extraction are major threats. Commercial rubber plantations, hunting, and trade of animals parts with China are all major threats to this species.

In China, hunting and habitat loss have reduced in population of this species, and it is locally extinct in some places.

In Thailand, habitat loss is a major threat, while hunting is prevalent, but not a significant threat to the species (R. Boonratana pers. comm.).

Conservation Actions

Internationally, this species is listed under Appendix II in CITES. Regionally, India lists it as schedule II under the Indian Wildlife (Protection) Act, 1972 (Srivastava and Mohnot 2001) amended up to 2002. The species is also protected in national wildlife acts of Lao PDR, Vietnam, Thailand, and Myanmar.

Stump-tailed macaques are found in a number of protected areas throughout their range, including: Balpakram National Park, Gibbon Wildlife Sanctuary, Mehao Wildlife Sanctuary, Murlen National Park (India); Huay Kha Khaeng Wildlife Sanctuary, Phu Khieo Wildlife Sanctuary (Thailand). They may possibly occur in Namdapha Wildlife Sanctuary and Pakhui Wildlife Sanctuary (India), and in Nam Ha National Biodiversity Conservation Area (Lao PDR).

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