Patterns of wounding in mixed-sex social groups of western lowland gorillas (Gorilla gorilla gorilla)

Death of a one-armed blackback male due to severe injuries in a group of wild western lowland gorillas (Gorilla gorilla gorilla) in Moukalaba-Doudou National Park, Gabon

The survival of limb-disabled primates in the wild has been widely reported. Nevertheless, their ultimate fate is little documented. It is important to understand the influence of limb disability on primate survival from a conservation perspective, as many African great apes suffer from limb injuries caused by entrapment in snares. Here, we report the death of a one-armed blackback male in a large one-male group of wild western lowland gorillas. The subject was a blackback male (14 years old) named Dodo, who lost his right forearm in August 2008. On 8 December 2019, Dodo was found to have suffered serious bleeding injuries to the front of his body, including large lacerations and puncture wounds. On 14 December his corpse was found in the forest. We provide evidence to suggest that his injuries were more likely caused by intraspecific aggression, though a predatory attack by a leopard could not be completely ruled out. His one-armed disability could have made him more vulnerable to attack from either a gorilla or leopard and led to his fatal injury. This report shows that a gorilla who had previously overcome a disability in one arm in childhood may die prematurely, in part, owing to this disability in young adulthood.

Survey of current group demographics and management practices of bachelor groups of western lowland gorillas (Gorilla gorilla gorilla) across North America

Recommendations for the successful management and maintenance of bachelor groups of western lowland gorillas (Gorilla gorilla gorilla) in zoological settings have been an increasingly prevalent focus within the zoological community. Over the past two decades, studies have examined the impact of various environmental factors on the stability of bachelor groups, proposed management strategies for bachelor groups, and compared behavioral trends between bachelor and mixed-sex groups. These studies have clearly demonstrated that bachelor groups are complex social units that require specialized management approaches. In this study, we aimed to assess the extent to which bachelor group management across North American zoos accredited by the Association of Zoos and Aquariums aligns with established recommendations. We distributed a comprehensive survey broadly encompassing habitat and housing, aggression and wounding, group demographics, feeding, and training to the 22 zoos housing bachelor groups as of 2019. We received completed surveys from 19 zoos, representing a total of 21 social units and 59 individual gorillas. We used descriptive statistics to represent the range of current management strategies across the surveyed population and ANOVAs to assess significant variation in key demographic variables. Our results demonstrate that a majority of zoos have adopted the best practices for the formation of social groups established by Stoinski et al. in 2004. However, there is much less standardization across zoos in protocols surrounding training and feeding. Additionally, important variables in the assessment of wounding, such as time of day and location, are often unknown or not observed by animal care professionals. We highlight these two areas as being of particular focus in developing and adhering to consistent protocols across institutions.

Is Chimpanzee (Pan troglodytes) Wounding Frequency Affected by the Presence Versus Absence of Visitors? A Multi-Institutional Study

Visitor effect studies have had inconsistent results, due in part to the inability to control for all confounding variables such as time of day, seasonal weather patterns, and so forth. This study represents the first instance where chimpanzee (Pan troglodytes) wounding frequencies were investigated across extensive time periods in the presence and complete absence of visitors, thus eliminating many visitor-related variables. Additional variables were eliminated through the zoo selection process, based on institutional responses to a 29-question survey, providing a novel approach to the question of visitor effects. The aim of this study was to determine if visitors were associated with a change in chimpanzee wound event frequencies across four 51-day time conditions, three of which occurred prior to the COVID-19 pandemic, and one during the first wave of pandemic-related zoo closures. We analyzed the archival records of 21 chimpanzees housed at three U.S. zoos. Due to the small number of wound events across all study windows, frequencies of “no wound” events were analyzed. A chi-square goodness of fit test was performed to determine whether the frequency of “no wound” events was equal between the “open” and “closed” trials. Results indicate that the frequencies did not differ, suggesting that chimpanzee welfare, as it relates to wounding, may not be adversely affected by zoo visitors.

Out of Sight, Out of Mind or Just Something in the Way? Visual Barriers Do Not Reduce Intraspecific Agonism in an All-Male Group of Nile Crocodiles (Crocodylus niloticus)

Simple Summary

The behavior of animals living in zoos and aquariums is influenced by the exhibits they live in, similar to how the behavior of animals in nature is influenced by the ecosystem they inhabit. In zoos and aquariums, changes in exhibit design can be implemented to modify the behavior of animals to ensure they are experiencing optimal welfare. Here, we evaluated if the addition of visual barriers—physical barriers placed at the surface of the water—reduce aggression amongst male Nile crocodiles living in a zoo. Both short- and long-term monitoring found that visual barriers did not reduce aggression within the group. While ineffective at reducing aggression, this study represents the first evaluation of exhibit design in relation to the behavior of a crocodilian species in a zoo or aquarium setting. As a commonly managed taxa in zoos and aquariums, it is imperative that their behavior and welfare are assessed systematically. We hope the methodologies and learnings from this study encourage future study of crocodilian behavior and welfare.

Abstract

Here, we evaluated if visual barriers could reduce intraspecific agonism in an all-male group of Nile crocodiles (Crocodylus niloticus) living in a zoo. Crocodiles were monitored for nearly 100 h, and four “hotspots” of aggression within their exhibit were identified. Within these four locations, visual barriers were placed at the surface of the water with the goal of reducing agonism by targeting sight lines associated with their species-typical minimum exposure posture, where crocodiles submerge their body but maintain facial sensory organs above the water line. Crocodile behavior was then monitored for 226 h, evaluating both short- and long-term effects of the visual barriers. In both observation periods, intraspecific agonism was unaffected by visual barriers. However, crocodiles were more likely to be on land and closer together, after the barriers were installed, showing the barriers affected nonagonistic behaviors. Monitoring of such unintended effects is significant to ensure no welfare concerns are created in any exhibit or husbandry modification attempt. Additionally, time of day and temperature were significant predictors of behavior, highlighting the importance of such factors in the analysis of reptilian behavior. While ineffective at reducing agonism, this is the first published study evaluating exhibit design and behavior of crocodilians in zoos and aquariums. The methodologies and findings here should provide useful information for future behavioral and welfare studies of this understudied taxa.