The purple-faced langur normally has a ‘unimale’ social system, usually consisting of one resident adult male (sometimes two), one to seven adult females and a number of subadults, juveniles and infants (2) (5). All-male groups also exist, numbering from 2 to 14 individuals, which split up to forage during the day and reform at the sleeping site at night. The home ranges of all-male groups overlap the home-ranges of unimale groups, but home ranges of unimale groups almost never overlap one another. The resident male will defend his territory aggressively against other males attempting to take over the harem (5).
A single offspring is born after a gestation period of 195 to 210 days. From 12 to 20 weeks the infant becomes more independent of its mother, beginning to eat solid food and engage in social play. Weaning occurs at seven to eight months. This diurnal species is largely folivorous, but will also feed on fruit, flowers and seeds (5).