FEMALE DOMINANCE RELATIONSHIPS AMONG CAPTIVE WESTERN LOWLAND GORILLAS: COMPARISONS WITH THE WILD

Female dominance relationships were studied among three family groups of western lowland gorillas (Gorilla gorilla gorilla) housed in large enclosures at Howletts Wild Animal Park, in Kent, England. In common with gorillas in their natural habitat, the Howletts gorillas forage throughout the day on low nutrient foods. However, the latter differ, at least from mountain gorillas (Gorilla gorilla beringei), in that they also have relatively frequent access to high nutrient, high energy novel food items which are patchily distributed in time and space, and defendable. It was predicted that, despite these differences, the Howletts females would resemble mountain gorillas in forming adult female dominance hierarchies (determined from supplant interactions) in which older females that have lived in the group the longest are dominant to younger females, more recent to the group. The comparison was made with mountain gorillas as they are the only gorilla subspecies for which such data exist for wild-living populations. As predicted, an age/tenure-based dominance hierarchy was found to be the case for those groups at Howletts where there was considerable variation between the females' ages and length of group tenure. As gorillas and chimpanzees resemble more closely each other in forming age/tenure-based dominance hierarchies than they do other female-transfer primate species, it is proposed that the gorilla-chimpanzee pattern may have common phylogenetic origins. In addition, the order of progression of gorillas into their indoor living quarters appears to be a good indicator of supplant-dominance relationships among adult group members. It was also found that, despite being removed from their natural habitat, dominant males in captivity still lead their groups during group travel in the same manner that do males in the wild: either at the head, or bringing up the rear. Though primate social behaviour may be flexible depending on immediate context and life history variables, this flexibility may well remain within evolutionarily defined parameters, leading to species-typical patterns in general social interactions.