An investigation into some effects of captivity on the behaviour of gorillas and chimpanzees in four British zoos

Abstract

This study, conducted at four British zoos over a period of four months, investigated some of the effects of captivity on the typical daily behaviour of 14 adult chimpanzees (Pan troglodytes) and 9 adult western lowland gorillas (Gorilla gorilla gorilla), focussing primarily on the influence of zoo visitors. Instantaneous time sampling was used to collect data on focal animals regarding ape behaviour, the apes' spatial location within the enclosure, and visitor characteristics (noisiness and crowd size). Apes were grouped into one of 10 categories for analyses, based upon which zoo they were from, their sex and whether they were dominant or non-dominant (males).Zoo animals are "on exhibit" for the whole of the zoo day, and are often unable to avoid the stares and noisiness of their human visitors should they want to. Zoo visitors, as a dynamic part of the captive environment, might be responsible for influencing the daily behaviour of the animals. This can have potential welfare implications and could also affect the zoo's success as a medium for conservation education. Four models were proposed based on the notion that apes experience some visitor characteristics as aversive and others as enriching. It was hypothesised that large or noisy crowds of visitors would affect the behaviour and spatial location of zoo- housed apes differently from small or quiet groups of visitors. The hypotheses were supported by the data. Results indicate that apes show various responses to visitors, with certain types of behaviour being affected in some species, age and sex classes, and not in others. From the data it is not clear whether the overall effects were enriching or aversive to apes, although some tentative suggestions have been made (based on the direction of changes in behaviour) suggesting that large or noisy groups of zoo visitors are an aversive presence.