Why can’t the boys play nice? Investigating drivers of agonistic behavior in an ex situ blacktip reef shark (Carcharhinus melanopterus) bachelor group

Agonistic interactions are necessary in the animal kingdom for defining hierarchy, accessing resources, and improving reproductive fitness. Aquaria and zoologic institutions strive to provide appropriate conditions to support the health and well-being of all animals in their care, however, even the best husbandry practices cannot always prevent intraspecific conflicts that may result in injury or fatality. The presence of a bachelor group of blacktip reef sharks (Carcharhinus melanopterus) at National Aquarium provides a unique opportunity to gain insight into a lesser known body of elasmobranch research, agonistic behaviors in an all-male social structure and their driving factors. This study identified male social hierarchy and subject feeding as two potential drivers of agonistic behaviors and hierarchy as an influence on engagement during subject feeding. Recorded and live observations of behavior through a change in population, across event types, and differences in feeding schedule were utilized to determine the frequency of agonistic behaviors associated with these variables and the frequency of subject engagement during feeding. Results showed that the frequency of agonistic behaviors Dart and Parallel Swim were significantly greater before the death of subject ‘2’ in January 2023 and during subject feeding events. They also demonstrated frequencies of engagement during subject feeding events correspond to the last known dominance hierarchy. These findings create a foundation for assessing drivers of agonistic behavior and the viability of using feeding engagement data to determine hierarchical structure in male ex situ blacktip reef sharks.