Visitor effects on three groups of zoo-housed primates

Visitors are an integral part of the zoo environment, and their presence may have a significant impact upon the animals housed in the zoo. In order to determine what effects visitors may have on zoo primates, I conducted studies on three species of primates in two zoos: Sulawesi crested macaques (Macaca nigra) at the Buffalo Zoo, Olive baboons (Papio anubis) at the Metro Toronto Zoo, and Western lowland gorillas (Gorilla gorilla gorilla) at the Metro Toronto Zoo. In the macaques study, I tested predictions for several hypotheses: that visitors cause stress for the monkeys, that visitors are enriching, that visitor-induced stress decreases monkey play, that play reduces visitor-induced stress, that visitor attention-getting behaviors (AGBs) increase visitor-directed aggression by the monkeys, and that visitors cause the monkeys to stay out of sight more often. In the baboon and gorilla studies, I tested the same predictions as with the macaques, but I also included the following: that social affiliation is suppressed by visitors, that social affiliation is a means of coping with stress caused by visitors, and that visitors cause increased intragroup aggression. I used all-occurrences sampling to record the frequencies of self-directed behaviors (SDBs) as a stress indicator, the rate of play bouts and aggressive episodes, visitor attention-getting behaviors (AGBs), and behaviors that the animals directed toward visitors. I also used scan sampling at 5-minute intervals record the number of visitors and decibel level, the presence of each animal, and whether each individual was engaging in affiliative behaviors. In the macaque study, I found little evidence of a relationship between visitors and either SDBs or play. The macaques tended to spend a smaller proportion of each session outside as the proportion of scans in which visitors were present increased. When visitors performed greater numbers of attention-getting behaviors (AGBs), the macaques tended to be more aggressive toward visitors, and the macaques were more likely to exhibit this type of aggression following AGBs than expected by chance. For the macaques, it seems that while visitors did not appear to influence play or rates of stress indicators, the results suggest that visitor behavior could have an impact upon welfare by increasing the macaques' likelihood of behaving aggressively. In the baboon study, I found that while there was some indication that the baboons engaged in social affiliation less as the average number of visitors increased, they also tended to play more as visitor presence, numbers, and decibel level increased. I also found that there was a positive relationship between baboon SDBs and visitor AGBs (though not other visitor variables), as well as a positive relationship between intragroup aggression and visitor numbers. For the baboons, it appears that visitors had a small, though potentially significant, impact on baboon welfare. In the gorilla study, I found that the gorillas performed fewer SDBs and played more when crowds were large. I also found that both SDBs and visitor-directed aggression increased as the rate of AGBs increased. The gorillas also tended to affiliate less with one another on days when the adjacent children's climbing structure was open. For the gorillas, it appears that visitors may have both positive and negative effects on the gorillas' welfare, with visitor AGBs being a crucial factor in the nature of that relationship. Because each study group was located in different enclosures at two zoos, was subject to unique management practices, and comprised a different species, it is not surprising that the results varied across groups. However, the overall results showed that visitors potentially have a negative impact on welfare, though it is possible that they also had a positive impact on the gorillas under certain conditions.