Public expectations for upholding welfare standards in all animal-based industries are as high as ever. Zoos experience a unique level of public scrutiny: they have their standards of care on display, open to judgement. In order to address public concerns over animal welfare, some zoos actively embrace the newest developments in animal welfare science. Studies indicate over and over again that zoo visitors care both about animal welfare and conservation efforts. But what effect do zoo visitors themselves have?

In this review, two Australian researchers carried out an audit of the available literature on the effects visitors have on the well-being of zoo animals. Past research in this field showed that the most common approach is to assess behavioral changes in response to different visitor conditions. Aggression, avoidance, and stereotypies have all been used as indicators of negative welfare states, associated with fear and stress, while exploratory, play, and affiliative behaviors have been interpreted as indicators of positive welfare states.

The conclusion of this overview is that there are findings across the entire range of possible effects: negative, neutral and positive, with the former dominating. The differences may be explained by several factors: 

• The way animals cope with stress is highly subjective, often dependent on the individual’s temperament and previous experiences.
• There is huge variation in the number of species housed at zoos. This leads to challenges in understanding species-specific factors that influence an animal’s response to humans. 
• Zoo species are often captive wild animals – they have not gone through the thousands of years of domestication that farmed and companion animals have. Therefore special means of evaluating the effects are needed.

Some examples of the negative effects include koalas disturbed when exposed to ‘loud’ crowds, chimpanzees avoiding foraging, grooming, and play, pumas and wolves becoming less active, and more. The researchers highlight that negative effects can be a result of the often unpredictable and intense auditory and visual behavior of the visitors. 

On the other hand, neutral responses may be a result of zoo animals becoming habituated to visitors, resulting in perceptions of visitors as a non-threatening part of their environment. Hopefully, this process does not come at a cost of repetitive acute or chronic stress. Although many species are reported to breed successfully and live longer than their wild counterparts, there are many who fare worse than expected, showing susceptibility to chronic stress related illnesses. There are also a few studies showing that visitors act as a positive stimuli for zoo animals, those these results are less conclusive.

Several studies across many species show that the ability for an animal to control its exposure to visitors can help in coping with the stress. Some studies actually highlighted that having options can be more important than using them. Another interesting finding was that covering the viewing windows with camouflaging net led to a combined effect of visitors perceiving a gorillas’ exhibit more positively, while also altering visitor behavior: people were quieter, more relaxed; they banged less on the glass and spoke less. 

Of course, there are many factors that may influence an animal’s response to visitors, including species evolutionary traits, individual animal traits, and the environmental set-up of the enclosure. The researchers report that it was difficult to draw any conclusions about the impact of species traits because of the disproportionate representation of studies across taxa – with most studies being carried out on non-human primates. Furthermore, there was a large variation in the methodology used to assess animal welfare.

The zoos, ostensibly conservation-oriented institutions, could benefit from learning that the way animals are presented to the visitors has an effect on how animals’ status is seen. For example, chimpanzees shown in the presence of humans implied that wild populations of chimps are stable, with a significant amount of visitors expressing their willingness to have one for a companion animal. However, viewers were more likely to describe the animals as “happy” when shown in the absence of people.

This review highlights that there is a need for more research into this topic, and that it needs an organized approach to evaluate such impacts. The research that already exists shows that visitors have an effect, and it’s mostly negative. This understanding should be applied like the precautionary principle, to either safeguard welfare when visitors might have a negative impact. Meanwhile, animal advocates should feel empowered to demand zookeepers not to compromise on the welfare of the animals at the gain of visits. There are clear indications that some animals feel distressed due to the presence and behavior of zoo visitors, an issue that can be addressed via not exhibiting such animals for people or, at the very least, by implementing changes in enclosure construction.