Wanderers Between Harems and Bachelor Bands: Male Hanuman Langurs (Presbytis Entellus) At Jodhpur in Rajasthan

Abstract

Abstract 1. Life-histories of individually identified males of an Asian colobine monkey, the Hanuman langur, were followed in order to understand mechanisms and functions of social processes associated with the formation of male bands, especially the degree of cooperation and competition among males. 2. The monkeys belonged to a geographically isolated population which is subject of a field-study in Rajasthan, India, spanning more than 15 years. The population consists of 27-29 one-male / multi-female troops ('harems'; average 39 members, home ranges up to 1.3 km2) and 12-14 all-male bands (average 12 members, moving ranges up to 20 km2). Females are highly philopatric, whereas males transfer from bisexual troops into male bands. Harem holder residencies average 27 months (range 3 days to more than 74 months). No male achieved residency in more than one troop, suggesting that residency is associated with a distinct peak in a given male's resource holding potential. The proportion of infants sired by extra-troop males is minimal. The dispersal pattern of langur males seem to reflect a long-lasting effort to achieve reproduction. This goal is tied to the necessity to rise through the ranks of a male band to the top of its dominance hierarchy, because only the highest ranking males can replace current harem holders during male band invasions into the home range of bisexual troops. 3. The age-class composition of seven male bands with a mean membership of 3-25 individuals was studied in detail. The longitudinal fluctuation in membership was less pronounced than the differences between bands. This reflects ecological conditions in the moving range of a given band which determine a ceiling in the number of members. The bands contained 27% juveniles, 23% subadults, 13% young adults, 30% prime adults and 9% old males. At any given time, in each band lived at least one individual who was of at least young adult age. Immatures often followed elder males during daily travels, but not