The Frequency of Solitary Behaviors in Captive Odontocetesis Modulated by Environmental and Social Factors

The number of welfare-oriented studies is increasing in animals under human care, including odontocetes. However, validated welfare indicators are lacking for captive odontocetes. We studied the effect of several conditions (moment of the day, social grouping, public presence) and stimuli (enrichment, perturbations) on the solitary behaviour of Yangtze finless porpoises (Neophocaena asiaeorientalis asiaeorientalis), East-Asian finless porpoises (N. a. sunameri) and bottlenose dolphins (Tursiops truncatus). The frequency of solitary play increased in the three groups in positive conditions and decreased in negative contexts, which confirms that play is a useful indicator of welfare for captive odontocetes. Jumping seem to be indicative of stress for finless porpoises but could be ambiguous for bottlenose dolphins: indicating both positive and negative excitation. Stereotypical behaviours for Yangtze finless porpoises and environment hitting behaviours for bottlenose dolphins could indicate mild stress or frustration. Vigilant behaviours are not clear indicators since a high frequency could reflect boredom, but a low frequency was observed in poor social conditions. Finally, we suggest that environmental rubbing should be investigated further since our results for this behaviour were not clear.