Preliminary observations on the ecology and behavior of the Capped Langur,Presbytis pileatus,in the Madhupur forest of Bangladesh

Between the rainy season months of July and November 1976, the author censused and intensively studied for 50 hr the capped langur,Presbytis pileatus, in the Madhupur Forest, Bangladesh. Transects were made in the forest to provide tree girth and height measurements. The predominant tree species is sal,Shorea robusta. The mean group size for capped langur troops observed in excess of 1 hr was 8.7, and that for troops censused for less than 1 hr, 7.5. Troops were primarily unimale, but one all-male band of four and a solitary adult male were sighted. The adult sex ratio of females to males was 2:1. The equivalent ecological density for intensively studied troops was 92 individuals/km². Estimated ecological biomass was equal to 716.5 kg/km². A daily activity profile shows that the capped langur has a bimodal feeding schedule. Midday is clearly a rest period. Adult males spend much time in sentinel behavior and an unusual penile display is described. Instances of intergroup antagonism are detailed. Fighting was observed on one occasion. Vocalizations are described by context of emission.