The northern plains gray langur (Semnopithecus entellus ), also known as the sacred langur, Bengal sacred langur and Hanuman langur, is a species of primate in the family Cercopithecidae.
The fur of adults is mostly light colored, with darker fur on the back and limbs, and the face, ears, hands and feet are all black. Infants are brown. Body size excluding tail ranges from 45.1 cm (17.8 in) to 78.4 cm (30.9 in) long, and the tail length is between 80.3 cm (31.6 in) and 111.8 cm (44.0 in). Adult males weigh between 16.9 kg (37 lb) and 19.5 kg (43 lb) while adult females weigh between 9.5 kg (21 lb) and 16.1 kg (35 lb).
The range of the northern plains gray langur covers a large portion of India south of the Himalayas south to the Tapti River and the Krishna River.It is thought to have been introduced to western Bangladesh by Hindu pilgrims on the bank of the Jalangi River.
The northern plains gray langur is diurnal, and is both terrestrial and arboreal. Its natural habitats are subtropical or tropical dry forests and subtropical or tropical dry shrubland. Females groom members of both sexes but males do not groom others.
The northern plains gray langur can live in several different types of groups. It can live in groups of multiple males and females, one male and multiple females or multiple males with no females, and males can also live alone without a group. Single male groups are most common. Group size can exceed 100 monkeys. Upon reaching maturity, males typically emigrate from their natal group while females typically remain. Young adult females are typically dominant over older females. When a new male takes over a group it may engage in infanticide of young fathered by the previous male or males, but this is less common when the takeover occurs slowly over several months.