Zoo animals often seem to ignore the presence of human visitors, but new research suggests that is not always the case for captive gorillas, which repeatedly become agitated and anxious when large numbers of people approach their exhibit.
The research, published in the current journal Applied Animal Behavior Science, is the first analysis on the influence of visitors on the behavior and welfare of zoo-housed gorillas.
"We noticed more behaviors suggestive of relaxation, such as increased resting, during low visitor density, and more behaviors suggestive of agitation, such as repetitive rocking, group-directed aggression and self-grooming during high visitor density," said the study's author, Deborah L. Wells.
Wells, a senior lecturer in the School of Psychology at Queen's University Belfast, Ireland, explained to Discovery News that she studied six western lowland gorillas housed together at Belfast Zoological Gardens in Northern Ireland. The gorilla group includes both wild-born and captive-born males and females of different ages.
The gorillas were observed for four hours a day on 20 busy days, when the average number of visitors was around 1,288. The gorillas also were observed on 20 quiet days, usually on weekdays when an average of six people visited the zoo.
During these periods, Wells documented known gorilla behaviors, such as standing, sitting, resting, grooming, aggression, playing, walking, running, climbing, socializing and banging on the viewing window. She also recorded "abnormal" behavior, like repetitive teeth clenching, body rocking and spinning.
Visitors seemed to have no effect on basic behaviors, such as standing, walking and socializing.