The role of touch in marine mammal sociality: a review and future directions

While social living has many advantages, it also has significant challenges associated with differences in individual interests, abilities, and intentions. Individuals in social species rely on diverse behaviours and signals across senses to mediate their relationships. In some species—particularly primates—touch plays a key role in establishing, affirming, and repairing social bonds. However, the degree to which touch is involved in pro-social behaviours in mammalian taxa is poorly understood. Marine mammals have unique adaptations to different levels of aquatic life and environments and display diverse social structures. They, therefore, represent a valuable source of comparison to deepen our understanding of the behavioural mechanisms that enable social living. Here, we examined current trends in research on social touch in marine mammals and evaluated existing evidence for its affiliative functions. Because of the logistical challenges associated with observing touch in species that spend most of their lives underwater, only a few odontocete species and captive populations dominate the existing literature. The prevalence of tactile interactions outside the mother-infant relationship is influenced by a species’ social structure. Still, we found that touch was involved in mediating a range of relations, from ephemeral and presumably anonymous to life-long individualized social bonds. We suggest leveraging emerging technologies, complemented by different behavioural data across modalities, long-term monitoring, and ensuring comparability to expand and deepen our understanding of how animals mediate their social relationships.