The effect of visitors on the behaviour of zoo-housed primates: A test of four hypotheses

Abstract

The effects of human visitors on the behaviour and welfare of zoo-housed primates have been extensively studied, and we know more about these effects in primates than in any other taxon. Nevertheless, it has proved difficult to detect an overall pattern in the responses of primates to visitors, as the presence of people can be stressful to the animals, but in some circumstances can be enriching, and in other circumstances the animals appear to be largely unaffected. Several potential causal factors have been suggested, namely that variability is due to species-specific differences, differences in visitor characteristics and behaviour, differences in housing and husbandry, or differences in individual characteristics of the animals, and these can be treated as four hypotheses to account for this variability in response. Here we test these four hypotheses using published data. A significant association was found between animal response and ecological category, such that small arboreal primates were most likely to be affected negatively. Visitor characteristics showed a significant association with animal response with noisy visitors having the most stressful effect. There was no significant effect of enclosure size or group size, though there was a significant association with enclosure type, such that animals in walk-through and semi-free range enclosures were more likely to show positive responses, though the small number of examples of these suggests treating this result with caution. Finally, individual differences were tested with gorillas, where there were sufficient data to look at individuals rather than animal groups. There was no significant effect of age or sex, but regression using all of the potential causal variables produced a significant model in which no individual predictor was significant, suggesting that it is the combination of predictors which influences the form of the response.