They have given their name to the rhesus antigens found in their blood in 1940, which has enabled doctors to determine different blood groups in humans. Rhesus monkeys were also the first primates to be rocketed into space.

Subspecies
Three subspecies.

Life span
Rhesus monkeys live for about four years in the wild, although in captivity, they can live for up to 30 years.

Statistics
Body length: 45-64cm, Tail length: 19-32cm, Weight: Males 6.5-12kg, Females 5.5kg.

Physical description
Rhesus monkeys have brown fur, and the adults have a red face and rump. The under-parts are lighter brown-coloured, and the hair on top of the head is short.

Distribution
Rhesus monkeys live in Afghanistan, India, Thailand and Southern China. They have been introduced to Florida.

Habitat
Rhesus monkeys prefer forest habitats, including semi-desert, dry, deciduous, bamboo, and tropical woodland up to 3000m.

Diet
They feed on seeds, roots, buds, fruit, invertebrates, bark and cereals.

Behaviour
Rhesus monkeys live in multi-male, multi-female troops. There is a matrilineal hierarchy (females lead the troop), although males are dominant to females. Males are peripheral to the group and are replaced every few years. Group size depends on environmental characteristics. In areas, where there is little water, groups of 200 may form. Rhesus monkeys are diurnal. They spend a significant proportion of their time on the ground.

Reproduction
After a gestation period of 135-194 days, females give birth to one infant, which weighs about 450g at birth.

Conservation status
Rhesus monkeys are classified as Lower Risk by the 2000 IUCN Red List.