Exploration of potential triggers for self-directed behaviours and regurgitation and reingestion in zoo-housed chimpanzees

The unique challenges faced by animals living in zoos can lead to the production of anxiety-related behaviours. In this study we aimed to understand what specific factors may cause chimpanzees to display these behaviours. In non-human primates, displacement behaviours, such as self-scratching and yawning, are considered markers of anxiety and stress, and Regurgitation and Reingestion […]

Do gorillas regurgitate potentially-injurious stomach acid during ‘regurgitation and reingestion?’

Regurgitation and reingestion (R/R) of foodstuffs is a common abnormal behaviour in captive western lowland gorillas (Gorilla gorilla gorilla) and certain other non-human primates, but it is not part of their normal feeding mechanism. It is similar to a behavioural problem seen in humans, human rumination syndrome (HRS), which can occur in association with anxiety […]

Implementing a low-starch biscuit-free diet in zoo gorillas: The impact on behavior

In the wild, western lowland gorillas travel long distances while foraging and consume a diet high in fiber and low in caloric density. In contrast, gorillas in zoos typically consume a diet that is low in fiber and calorically dense. Some items commonly used in captive gorilla diets contain high levels of starch and sugars, […]

The effect of a diet change on regurgitation and reingestion in captive chimpanzees

Captive chimpanzees regularly show abnormal behaviour, including regurgitation and reingestion (R/R). R/R may have several causes, among them a suboptimal diet. For this reason, the effect of a diet change towards a more fibre-rich diet on R/R was studied in the Amersfoort Zoo chimpanzee group comprising 15 individuals. In addition, the relationship with self-directed behaviour, […]

Behavioral and hormonal responses to the availability of forage material in Western lowland gorillas (Gorilla gorilla gorilla)

We investigated how forage material affects indicators of welfare in three male Western lowland gorillas (Gorilla gorilla gorilla) at the Detroit Zoo. In addition to their maintenance diet and enrichment foods, the gorillas generally received forage material four times a week. From this baseline, we systematically manipulated how much forage material the group received on […]