Patterns of visually observable behaviour and vocalizations in groups of female sperm whales

In groups of female and immature Physeter macrocephalus off the Galapagos Islands multivariate analysis showed the rates of performing visually observable activities and vocalizing to be largely represented by an axis termed Sociality. About 3/4 of the time sperm whales engaged in relatively stereotyped foraging for food, diving regularly, moving steadily, appearing only briefly at the surface in small clusters, and making regularly spaced trains of "usual' clicks. However, for periods which usually lasted either about one or about five hours, and often in the afternoon, the whales would aggregate at the surface, usually in large, slow-moving clusters, often making patterned series of clicks called "codas'. There was considerable variation in the behaviour observed, and sounds heard, during these periods of Aggregation. Results are consistent with the hypothesis that a primary function of periods at the surface is the maintenance of social bonds. -from Authors