Macaques

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Macaques

Macaques are medium- to large-sized monkeys native to Asia and Africa belonging to the genus Macaca, family Cercopithecidae, order Primates. Macaques are usually various shades of brown, gray, or black in fur color, although golden and white color phases occur rarely. Approximately 16 species are known. Locomotion is mainly quadrupedal, and most species are terrestrial in habit, although they take readily to trees, and a few species are primarily arboreal. Body weights range from 8-40 lb (3.5 kg-18 kg) for adult males, and from 5-36 lb (2.5-16.5 kg) for females; thus they vary from the size of a small dog, such as a beagle, to a moderate-sized border collie or dalmatian. Tails in different species vary from small stub like tails in the Barbary macaques, or Sulawesi macaques, to long graceful tails 2 ft (70 cm) in length.

The most famous macaques are the rhesus monkey of India, Nepal, and China; the Japanese monkey of Japan; and the crab-eating or long-tailed macaques of Thailand, Malaysia, the Philippines, and Indonesia. All of these play an important part in the cultural history of their countries, and all are well represented in folk-tales, dance, drama, and religious beliefs. Also well-known in popular literature is the “Barbary ape,” properly called the Barbary macaque in North Africa and Gibraltar, and the “Celebes ape,” properly called the Celebes macaque, of Sulawesi, Indonesia. Both species were incorrectly called “apes” because their small stub-tails make them appear tailless, and in the case of the Celebes macaques, their black coats give them the appearance of small chimpanzees.

Macaques have the widest geographic and ecological ranges of any nonhuman primates. Their geographic range includes Morocco and Algeria in northwest Africa, home of Macaca sylvana, the Barbary macaque, to the broad expanses of Asia from Afghanistan to northern China, Japan, Taiwan, Philippines, Southeast Asia, and Indonesia as far east as Sulawesi and the Molucca Islands. No other group of nonhuman primates has such an extensive geographic range.

Ecologically, macaques live in a great variety of habitats from tropical rainforests of southeast Asia, to the agricultural plains of northern India, the deserts of Rajasthan, the arid mountains of Pakistan and Afghanistan, and even temperate snow-capped mountains of Japan, northern China, Nepal, and Morocco. Several species are also conspicuous commensal inhabitants of villages, temples, towns, and cities in Asia, especially the rhesus monkey in India and Nepal, the Japanese monkey, and the crab-eating monkey of Southeast Asia and Indonesia. One species alone, the rhesus monkey, Macaca mulatta, is both a close commensal associate of human populations in the crowded cities of India, and an inhabitant of cool pine forests in northern India.

The widespread ecological and geographic distribution of the macaques is a reflection of their great adaptability to different climates and habitats. Many species of macaques can tolerate wide temperature regimes, thrive on a great variety of natural or agricultural foodstuffs, and live in very different landscape settings from the mangrove forests of the Gangetic delta, to the steep slopes of the Himalayas. They readily adapt to people, can survive well in urban environments if allowed to steal food, but they can also exist without humans in completely natural habitats.

In food habits, macaques are mainly vegetarian, although some species have been observed to feed on insects for a small part of their diet. In forest habitats, macaques are known to consume parts of more than 100 species of plants, primarily fruits, but also buds, young leaves, twigs, bark, and occasionally flowers, and even roots. In agricultural habitats, where macaques live in close association with people, they are notable crop raiders, feeding on field crops such as wheat, rice, and sugar cane, and on garden crops such as tomatoes, melons, bananas, papayas, and mangos.

In commensal habitats such as towns, villages, temples, and roadsides, they also feed extensively on direct food handouts from people—food such as peanuts, rice, grams (a type of legume like a soybean), and even prepared foods including chapatis. In India, one study showed that a roadside group of rhesus monkeys in a populated portion of the Gangetic Basin east of New Delhi obtained 83% of its food from people, 10% from agricultural field crops, and only 7% from natural vegetation. In contrast, a forest-dwelling group near Dehra Dun obtained virtually all of its food from natural forest vegetation. Other forest-dwelling species such as the lion-tailed macaque of south India, Macaca silenus, obtain all of their food from natural vegetation, as do most of the Sulawesi macaques such as Macaca nigra and Macaca tonkeana. The latter, however, have taken to crop raiding recently as homesteaders and farmlands invade their natural forest habitats.

Macaques are intensely social animals, living in established social groups of just a few to several hundred individuals. A typical social group of macaques has 20-50 individuals of both sexes and all ages, consisting normally of approximately 15% adult males, 35% adult females, 20% infants, less than one year of age, and 30% juveniles one to four years of age. However, there is great variation in group sizes and structures.

The macaques living in temperate environments such as northern India, China, and Japan, have mating seasons, usually in the late fall (September-December), with most births occurring in the spring and early summer (late March-July). Gestation periods average around 160 days, varying from 145-186 days. Usually only one young is born at a time. Twins are rare. In different species and different populations, 30-90% of the adult females give birth to one young per year. Infant macaques are carefully cared for, nursed, and protected by the mother for many months, and weaning usually occurs nine to 12 months after birth when the next infant is born. Infants are bright-eyed and active but remain in close contact with the mother for several weeks. After six to eight weeks, they begin to explore on their own, leaving their mother briefly, beginning to play with other infants in games of wrestling and chasing. They return to their mother, however, when she shows signs of moving. They ride with her wherever she goes, at first clinging to her belly, but after several months, they often ride on her back.

After one year of age, macaques pass from infant dependency on their mother to a juvenile status, where they associate more frequently with other juveniles. This is the period of most active rough and tumble play. They become sexually mature at three to five years of age. Females normally stay within the social group to which they were born, whereas young adult males often disperse and try to enter other social groups. This can be a time of aggressive activity, and not all males successfully enter new groups. Some may become solitary, and continue attempts to join social groups for many years. If successful adulthood is reached within a social group, macaques have a normal longevity of 20-25 or even 30 years.

The reproductive potential of some species, such as the rhesus monkey, enables populations to grow at rates of 10-15% per year if all environmental conditions are favorable. Other species, especially the forest dwelling lion-tailed macaque and some of the Sulawesi macaques, however, have much lower reproductive rates, and their populations are actually endangered.

Macaques have been subjects of great scientific interest for many years in both field and laboratory studies. Field studies have focused on their fascinating ecology, behavior, and adaptations to a wide range of habitats. Laboratory studies of behavior have involved research on intelligence, learning, social development, and communication. In research at the University of Wisconsin, and Cambridge University, England, for example, it has been shown that the maternal-infant bond is essential for normal behavioral development. Without proper mothering, young macaques fail to develop all the social and communicative skills for successful life in a social group. Some of these social deficits may be relieved with adequate peer group experience, but in any case, the overwhelming importance of the social environment is evident. Adult males do not participate in infant care, except in a few species and occasional individuals. The Barbary macaque is notable for adult males taking an active role in carrying and holding infants, and even in rhesus macaques, where infant care is normally the sole province of the mother, occasionally an adult male will show interest in holding infants. This is rare, however. Usually, fatherhood is not readily recognizable—mating behavior of most macaques is promiscuous, and a female may mate with more than one male in an estrous cycle.

Macaques have a number of basic similarities in anatomy and physiology to humans, and for this reason they have been used extensively in biomedical research, vaccine development, and pharmaceutical testing. The rhesus monkey was the primary subject, for example, in research, development, and testing of polio vaccines and in discovering principles of human blood antigens such as the Rh factor. Rhesus monkeys have also been valuable as research subjects in cardiovascular diseases, cancer, immunology, toxicology, orthopedics, cerebral palsy, and a variety of infectious diseases. Macaca nigra has been important in diabetes research, and Macaca nemestrina in research on retro-viruses and AIDS. The use of primates in biomedical research is a controversial subject, strongly opposed by animal rights groups, but generally supported as necessary and beneficial by most biomedical scientists, providing adequate safeguards are taken to assure humane treatment and proper care.

The extensive uses of macaques in biomedical research, along with habitat loss and other ecological pressures, have severely depleted the numbers of some species. Certain conservation measures have resulted in some recoveries of declining populations, however, especially of rhesus and Japanese monkeys. The rarer species of macaques, including the lion-tailed, Celebes, Celebes black, and Mentawai macaques, are seriously endangered, however, mainly because of habitat losses. Strong action on conservation protection is needed for these species, as well as for many other non-human primates.

Whenever groups of macaques are displayed in zoos they form popular exhibits with their active patterns of social interaction: grooming, maternal care, infant and juvenile play, and occasionally, adult conflict and aggression. We can often see reflections of our own personalities in their behavior. In Asia, these similarities have been encoded into rich cultural attachments, especially in Hinduism, Buddhism, and the religions of China, where macaques play an important role in religious traditions and folklore. In both India and China, for example, macaques and other primates enjoy the status of gods capable of defeating evil and restoring justice to human life. Throughout the world, macaques enrich our lives in many practical and intangible ways.