The seven species of short-tailed macaques on the Indonesian island of Sulawesi ( Celebes) vary in appearance from the distinctive Celebes black “ape” (Celebes crested macaque) (M. nigra) at the northern end of the island to the less-specialized Moor macaque (M. maura) in the south. Most of the Sulawesi species are in danger of extinction. Crab-eating, or long-tailed, macaques (M. fascicularis) of Southeast Asia have whiskered brown faces; they live in forests along rivers, where they eat fruit and fish for crabs and other crustaceans. In the 1950s they were used extensively in studies that led to the development of the polio vaccine. Macaques in general, including the rhesus monkey (M. mulatta), are the monkeys most widely used in biomedical research. Rhesus monkeys are native to northern India, Myanmar (Burma), Southeast Asia, and eastern China, formerly as far north as Beijing. The Formosan, or rock macaque (M. cyclopis), is closely related to the rhesus monkey and lives only in Taiwan. Japanese macaques (M. fuscata) are larger, more muscular, and shaggy-haired, with pink faces and very short furry tails. These monkeys are important figures in myths and folktales and are seen in representations of the Buddhist adage “See no evil, hear no evil, speak no evil.”

Liontail macaques, or wanderoos (M. silenus), are black with gray ruffs and tufted tails; an endangered species, they are found only in a small area of southern India. Closely related to liontails are the pigtail macaques (M. nemestrina), which carry their short tails curved over their backs. Inhabiting rainforests (rainforest) of Southeast Asia, they are sometimes trained to pick ripe coconuts. Another close relative is the bokkoi (M. pagensis), found only on the Mentawai Islands of Indonesia.

Stump-tailed macaques (M. arctoides) are strong, shaggy-haired forest dwellers with pink or red faces and very short tails. Another short-tailed species is the Père David's macaque (M. thibetana), which lives in mountain forests of southern China; it is sometimes called the Tibetan macaque but is not in fact found there. Often confused with the stump-tail, Père David's macaque is in fact more closely related to the longer-tailed Assam macaque (M. assamensis) from the eastern Himalayan foothills and northern Myanmar. The bonnet monkey (M. radiata) and the toque macaque (M. sinica), from southern India and Sri Lanka, respectively, have hair on the top of the head that grows from a central whorl, in contrast to the short hair of the forehead and temples.

The genus Macaca is a primate classified in the family Cercopithecidae (Old World monkeys), along with baboons, mangabeys (mangabey), guenons (guenon), langurs (langur), and colobus monkeys.