Group structure and individual relationships of sanctuary-living Grauer’s gorillas (Gorilla beringei graueri)
The study of individual social relationships and group structure provides insights into a species’ natural history and can inform management decisions for animals living in human care. The Gorilla Rehabilitation and Conservation Education (GRACE) center provides permanent sanctuary for a group of 14 Grauer’s gorillas (Gorilla beringei graueri), a critically endangered and poorly studied subspecies […]
Comparing Predictors and Outcomes of Higher Allostatic Load across Zoo-Housed African Great Apes
Stressors over the lifespan can contribute to physiological dysregulation, or allostatic load. Allostatic load has been studied in humans using allostatic load indices (ALIs) for over 25 years, but the same methods are rarely applied to other species. We constructed an ALI for zoo-housed western lowland gorillas, chimpanzees, and bonobos and tested potential predictors of […]
Gorilla Activities and Social Behavior: Assessing Changes Associated with Absence of Zoo Visitors, Zoo Attendance, Time of Day and Increasing Maturity
In this study we report on associations found between several variables and changes in gorilla behavior. Two groups of gorillas were observed, one was a family group and the other was a bachelor group. The zoo was closed to visitors for two periods during the COVID-19 pandemic which made it possible to document any differences […]
Comparing Space Use and Fecal Glucocorticoid Concentrations during and after the COVID-19 Closure to Investigate Visitor Effects in Multiple Species
We used the COVID-19 pandemic closure at the Saint Louis Zoo to examine visitor effects on space use and glucocorticoid levels in banteng, grizzly bears, polar bears, and western lowland gorillas. The study was divided into four six-week phases: closure in spring 2020, reopening in summer 2020, fall 2020, and spring 2021 as a seasonal […]
Urinary oxytocin and cortisol concentrations vary by group type in male western lowland gorillas (Gorilla gorilla gorilla) in North American zoos
Evaluating how primates in human care function within their social environment is important for understanding and optimizing their management and welfare. The neuroendocrine hormone oxytocin is associated with affiliation and bonding, suggesting it can be used to evaluate the affiliative nature of social groupings. When paired with cortisol concentrations, social stressors can simultaneously be assessed, […]
What’s not to like about Likert? Developing a nonverbal animal preference scale (NAPS)
Rating scales, such as Likert scales, are incredibly flexible and intuitive tools for measuring individuals’ rating of agreement with or relative preference for many types of stimuli. For humans, this typically involves ratings of agreement between end points representing distinct attitudes or beliefs; For example, strongly disagree to strongly agree. Nonverbal versions of Likert scales […]
Social proximities of developing gorilla males (Gorilla gorilla gorilla) in European zoos: the consequences of castration and social composition
In the European captive population of western lowland gorillas (Gorilla gorilla gorilla), the harem social structure and an even sex ratio at birth result in a surplus of males and consequent management difficulties. This study seeks to assess the socialization differences between captive juvenile and adolescent male gorillas according to their fertility status (intact vs […]
An investigation into keeper opinions of great ape diets and abnormal behaviour
Zoos are evidencing a shift in great ape diets to cultivated fruit-free to achieve a more wild-type nutritional composition (lower sugar, higher fibre). This study aimed to ascertain great ape keeper knowledge and opinions on the removal of cultivated fruit from great ape diets, to investigate feeding regimes currently in use and to understand the […]
Gorillas (Gorilla gorilla gorilla) Fail to Learn Abstract Cues of Differential Outcomes in a Novel Cognitive Bias Test
In order to assess mood state in three male western lowland gorillas housed in a bachelor group, we developed a novel version of a cognitive bias task. The background color of a touchscreen presented a conditional ‘if, then…” rule relating to outcomes involving differential amounts of food rewards. The gorillas struggled to reach a criterion […]
Visitor effects on anxiety in two captive groups of western lowland gorillas
There is growing interest in examining the effects that visitors have on the welfare of zoo primates. Most recently, the importance of evaluating the combined impacts of visitors and management practices on anxiety levels of these animals has been highlighted. Studies that take such an approach have the potential not only to highlight how visitors […]