Life history of Hanuman langurs (Presbytis entellus). Reproductive parameters, infant mortality, and troop development.

Longitudinal data of reproductive parameters from two langur troops (Presbytis entellus) at Jodhpur, Rajasthan, India, are presented. Females can reach menarche at approximately 29 months of age and conceive about 5 months later. Gestation length is about 200 days, average cycling length is 24 days, and mean interbirth interval 15.3 months. Postpartum amenorrhea, which ranges from 80-140 days will be reduced to 23-80 days in cases of stillbirths or early losses of infants, a fact that bears consequences in regard to the discussion of infanticide and reproductive advantage. Troop development showed distinct differences in two neighboring troops, especially in number of surviving female infants until sexual maturity. Both troops taken together, 77.9% of the newborns reached the infant-II stage (6 months), 59.3% survived until their mother's next infant (average, calculated for the mean birth interval of 15.3 months), and only 35.9% completed the 2nd year of life.