Social play varies among species and individuals and changes in frequency and duration during ontogeny. This type of play is modulated by environmental changes (e.g., resource availability). In captivity, cetaceans and their environment are managed by humans, and training sessions and/or public presentations punctuate the day as well as other frequent or occasional events. There is a lack of research on the effects of environmental events that occur in captivity and might affect dolphins' behavior. We studied the context in which nine bottlenose dolphins (Tursiops truncatus) played socially and the events that could potentially impact this social interaction. The dolphins' social play behavior was significantly more frequent and lasted longer in the morning than in the afternoon and was present before and after interactions with their trainers with a non-significant tendency to be more frequent before and after a training session than a public presentation. In an experimental paradigm using familiar environmental enrichment, our results demonstrated that environmental enrichment tended to increase social play duration whereas temporary noisy construction work around the pool and display of agonistic behaviors by members of the group significantly decreased it. These results contribute to better understand the social play distribution in captive bottlenose dolphins and the impact of different events within their daily lives. Since play decreases or disappears when animals are facing unfavorable conditions, the evaluation of social play may relate to the animals' current well-being. We suggest that social play has potential to become an indicator of bottlenose dolphins' current welfare state.

Research on the welfare of captive odontocetes has increased in recent years, but has been mostly focused on bottlenose dolphins (Tursiops truncatus). Few studies investigated potential welfare indicators using quantitative data linked to a range of conditions or stimuli that are thought to impact the animals’ emotional state. Since odontocetes are social animals that engage in various social interactions, these interactions might inform us on their welfare state. We investigated pectoral contact laterality and the effect of the context on several social behaviors in three groups of captive odontocetes (Yangtze finless porpoises, YFPs: Neophocaena asiaeorientalis asiaeorientalis; East-Asian finless porpoises, EAFPs: N. a. sunameri, and bottlenose dolphins, BDs). Animals exhibited patterns depending on the time of the day for most of the social behaviors we analyzed; social separation was associated with lower rates of social behaviors for the two analyzed groups (YFPs and BDs), the accessibility to several pools was associated with higher rates of social behaviors for BDs. The effect of enrichment, disturbances and public presence was less clear and strongly depended on the group, the type of enrichment and disturbance. Our results confirm that captive odontocetes’ social behaviors are influenced by the context, and that, depending on the group, some of them, such as pectoral contacts, other body contacts, agonistic interactions or social play exhibit consistent patterns across contexts. Monitoring these behaviors might be useful to adapt the captive management to each species and group. The different responses among the three studied groups confirm that species and groups react differently to a stimulus and therefore, management decisions should be species/group specific. We recommend that more studies should be conducted to validate our findings in other groups of odontocetes under human care.

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