Gorilla adaptations to naturalistic environments

Abstract

In the past few decades there have been increased investigations into the effects of captive environments on behavior. Simultaneously, zoological gardens have undergone a revolution in philosophy and design, resulting in a proliferation of “naturalistic” habitats. Complex environments such as these have been found to affect the behavior of captive animals favorably, including increasing reproductive and rearing success, encouraging the expression of species‐typical behavior patterns, and decreasing abnormal behaviors. In June 1988, Zoo Atlanta completed four naturalistic habitats for western lowland gorillas (Gorilla gorilla gorilla). These new habitats afforded a unique opportunity to study the adaptation of lowland gorillas to novel, naturalistic habitats. During the first year of habitation, a total of 451 hours of data were collected on 11 gorillas housed in three harem groups. Focal animal sampling with a behavioral change scoring system was used to obtain information on behavior, substrate, environmental components utilized, and location in sun or shade. Instantaneous scans at 15 minute intervals provided information on location and behavior of all individuals. Adaptation to the environments was assessed by using the indices of: time spent manipulating objects across the course of the study, the percent of the habitats utilized, and the dispersal of individual animals over the habitats. Trends in these behaviors indicated that exploration of the environments significantly decreased, but that this decline in exploration took over six months to occur. Several interpretations of these findings are presented including the unfamiliarity of these naturalistic habitats to these subjects.