Rhesus macaque

Appearance

The Rhesus macaque is brown or grey in color and has a pink face, which is bereft of fur. Its tail is of medium length and averages between 20.7 and 22.9 cm.

Adult males measure approximately 53 cm on average and weigh about 7.7 kg. Females are smaller, averaging 47 cm in length and 5.3 kg in weight. Rhesus macaques have on average 50 vertebrae. Their intermembral index is 89%. They have dorsal scapula and a wide rib cage.

The Rhesus macaque has 32 teeth with a dental formula of 2.1.2.3/2.1.2.3 and bilophodont molars. The upper molars have four cusps: paracone, metacone, protocone and hypocone. The lower molars also have four cusps: metaconid, protoconid, hypoconid and entoconid.

Naming

The name "rhesus" is reminiscent of the Greek mythological king Rhêsos. However, the French naturalist Jean-Baptiste Audebert who applied the name to the species, stated that it had no meaning.

Distribution

Rhesus macaques are native to northern India, Bangladesh, Pakistan, Nepal, Burma, Thailand, Afghanistan, Vietnam, southern China, and some neighboring areas. The Rhesus monkey has the widest geographic ranges of any nonhuman primate, occupying a great diversity of altitudes throughout Central, South and Southeast Asia.

Behavior

Rhesus macaques are diurnal animals, and both arboreal and terrestrial. They are quadrupedal and, when on the ground, they walk digitigrade and plantigrade.

In psychological research, Rhesus macaques have demonstrated a variety of complex cognitive abilities, including the ability to make same-different judgments, understand simple rules, and monitor their own mental states.

Habitat

Inhabiting arid, open areas, Rhesus macaques may be found in grasslands, woodlands and in mountainous regions up to 2,500 m in elevation. They are regular swimmers. Babies as young as a few days old can swim, and adults are known to swim over a half mile between islands, but are often found drowned in small groups where their drinking waters lie. Rhesus macaques are noted for their tendency to move from rural to urban areas, coming to rely on handouts or refuse from humans.

Reproduction

Adult male macaques try to maximize their reproductive success by entering into consort pairs with females, both in and outside the breeding period. Females prefer to mate with males that will increase the survival of their young. Thus a consort male provides resources for his female and protects her from predators. Larger, more dominant males are more likely to provide for the females.

The breeding period can last up to 11 days, and a female usually mates with four males during that time. Male rhesus macaques have not been observed to fight for access to sexually receptive females, although they suffer more wounds during the mating season. Female macaques first breed when they are four years old, and reach menopause at around 25 years of age. Male macaques generally play no role in raising the young but do have peaceful relationships with the offspring of their consort pairs.

Mothers with one or more immature daughters in addition to their infants are in contact with their infants less than those with no older immature daughters. This is because the mothers may pass the parenting responsibilities to her daughters.

High-ranking mothers with older immature daughters also reject their infants significantly more than those without older daughters, and tend to begin mating earlier in the mating season than expected based on their dates of parturition the preceding birth season. Infants farther from the center of the groups are more vulnerable to infanticide from outside groups. Some mothers abuse their infants which is believed to be the result of controlling parenting styles.

Food

They are mostly herbivorous feeding on mainly fruit, but also eating seeds, roots, buds, bark, and cereals. It has been estimated that they consume around 99 different plant species in 46 families.

During the monsoon season, they get much of their water from ripe and succulent fruit. Macaque living far from water sources lick dewdrops from leaves and drink rain water accumulated in tree hollows. They have also been observed eating termites, grasshoppers, ants and beetles.

When food is abundant, they are distributed in patches and forage throughout the day in their home range. They drink water when foraging and gather around streams and rivers. Rhesus macaques have specialized pouch-like cheeks, allowing them to temporarily hoard their food.