The assessment of animal welfare relates to investigations of how animals try to cope with their environment, and how easy or how difficult it is for them to do so. The use of rigorous scientific methods to assess this has grown over the past few decades, and so our understanding of the needs of animals has improved during this time. Much of the work in the field of animal welfare has been conducted on farm animals, but it is important to consider how the methods and approaches used in assessing farm animal welfare have been, and can be, adapted and applied to the measurement of welfare in animals in other domains, such as in zoos. This is beneficial to our understanding of both the theoretical knowledge, and the practicability of methods. In this article, some of the commonly-used methods for measuring animal welfare will be discussed, as well as some practical considerations in assessing the welfare of zoo animals.

Research indicates that regurgitation and reingestion (R/R) is a relatively common behaviour in zoo-housed great apes, with most work to date carried out on Western lowland gorillas Gorilla gorilla gorilla and Chimpanzees Pan troglodytes. It is an abnormal behaviour because great apes are not anatomically adapted to regurgitate their food as part of their normal feeding processes, and because this behaviour is not seen in members of the species living freely in the wild, in conditions that would allow a full behavioural range. In this article, I give an overview of the published literature on R/R in great apes, which suggests that this behaviour is probably multifactorial and may be linked to inappropriate feeding environments (e.g. in terms of nutritional composition of the diet and/or presentation of food), and possibly also social and other factors as well. A similar behaviour to R/R, known as rumination disorder, can also occur in another great ape species, humans, in whom it is classified as a feeding and eating disorder, and there are potential consequences to people's physical health as a result of oral acid. There have been no known studies to date to identify whether or not similar health consequences can occur in non-human great apes, but the regurgitant has been found to be significantly more acidic in gorillas than the food they ingested originally, meaning it is potentially injurious in non-human great apes. There is much that is not yet known about this behaviour and how to reduce or eliminate it when it does occur, as the research indicates that there are a range of factors involved, and these can vary by individual animal. More research into this behaviour is clearly needed to ensure that zoos and sanctuaries are providing the best possible care for these animals, and I make some suggestions for future research directions.

23Chimpanzees in laboratory colonies experience more wounds on week days than on weekends, which 24 has been attributed to the increased number of people present during the week; thus the presence of 25 more people was interpreted as stressful. If this were also true for primates in zoos, where high 26 human presence is a regular feature, this would clearly be of concern. Here we examine wounding 27 rates in two primate species (chimpanzees Pan troglodytes and ring-tailed lemurs Lemur catta) at 28 three different zoos, to determine whether they correlate with mean number of visitors to the zoo. 29Wounding data were obtained from zoo electronic record keeping system (ZIMS™). The pattern of 30 wounds did not correlate with mean gate numbers for those days for either species in any group. We 31 conclude that there is no evidence that high visitor numbers result in increased woundings in these 32 two species when housed in zoos. 33Keywords: aggression, captivity, visitor effect, animal welfare.