Rhesus monkey

Rhesus monkey (Maccaca mulatto), monkey found in southern and south-eastern Asia. Its use in medical and behavioral research led to the discovery of the Rh factor, a substance found in human red blood cells. Rhesus monkeys measure 18–25 in (48–64 cm) and weigh from 9–22 lb (4–10 kg) with a tail of 7–12 in (18–30 cm). They live in deserts, farm areas, forests, mountains and swamps. They eat birds, fruit, insects, leaves, roots, and farm crops.