Playing on the edge of the sea: a comparative analysis in Otariids and Odobenids

The role of play in the superfamily Otarioidea has not been widely explored. However, all play types found in other so-called “playful groups” (e.g., primates or canids) have been reported among sea lions, fur seals and walruses. Otariids and odobenids perform object play with animate and non-animate objects, such as kelp, rocks or seabirds. Locomotor-rotational play in otariids is mainly performed at sea, where animals exhibit complex and sophisticated movements such as pirouettes, torpedoes and somersaults. In the same family, play-fighting is the most common form of terrestrial social play, and is composed of competitive behavioral patterns that are exchanged between players. As in other mammalian species, in otariids play distribution follows a skewed bell-shape developmental curve, starting in infancy, peaking in juvenility and disappearing in adulthood. The distribution and modality of this behavior reflect the level of the sociality of a given species. In those species characterized by high levels of tolerance and maternal permissiveness, social play starts earlier in ontogeny. During play-fighting, play signals are displayed and exchanged between players to avoid escalating into aggression. In other mammalian taxa, the same signals have been reported and seem to serve the same purpose (e.g., Relaxed Open Mouth, “ROM”). Testing hypotheses on the evolution of play requires that many species with diverse habits (e.g., terrestrial, aquatic, arboreal) and kinds of sociality (e.g., despotic, tolerant) are studied using a comparative perspective. Herewith, the superfamily Otarioidea can be important to help understand this puzzling set of behaviors.