The Diana monkey (Cercopithecus diana) is often considered one of the most beautiful of the Old World monkeys. It is found in West Africa, from Sierra Leone to Ghana.
The Diana monkey ranges from 15.75 to 21.65 in (40 to 55 cm) long, excluding its tail. The tail is of a uniform 1.18 to 1.57 inches (3 to 4 cm) in diameter and 19.69 to 29.53 in (50 to 75) cm long. They are generally black or dark grey, but have a white throat. They have a crescent-shaped brow band, ruff and beard. The monkeys’ underarms are also white, and they have a white stripe down their thighs. The backs of their thighs, and their lower backs, are a chestnut color. Their fur is short and sleek in appearance. Adults weigh between 8.82 and 15.43 pounds (4 and 7 kg).
The Diana monkey is found in the prehistoric forests, and does not thrive in secondary forests. It is active during the day. It rarely comes down to the ground, but feeds at all levels of the canopy. They retreat to the upper levels of the trees at night, though it does not make nests. Its marked coloration allows a wide range of visual social signals. It also has a wide range of alarm calls, with different sounds for different predators. It is a noisy presence in the forest. It feeds mainly on fruit and insects, but will also take flowers. They also eat young, leaves, and invertebrates. Their predators consist of crowned hawk-eagles, leopards, chimpanzees and humans. The monkey has distinctive alarm calls for different kinds of predators
Individual Diana monkeys may live for up to 20 years. Groups consist of a single male with a number of reproducing females and their infants. In good conditions, adult females reproduce annually. Gestation lasts about 5 months, and the young nurse for a further six months. Normally only a single infant is born. They are born in a fairly well developed condition, with open eyes and able to grasp their mother. In zoo conditions, Diana monkey mothers appear anxious and possessive. They rarely let young infants leave them. As infants grow, however, they become very playful. Juveniles reach sexual maturity at an age of about 3 years. Daughters remain in their mothers’ social groups. The males leave their natal groups shortly before attaining sexual maturity.
The Diana monkey can carry diseases that can be communicated to humans, like yellow fever and tuberculosis. They are not important carriers of these.