The majority of whales that live surrounded by members of their own species are odontocetes (toothed whales). They are divided into two types of social organizations: fusion-fission societies and matriarchal groups. As a rule, smaller species tend toward the former and larger species toward the latter.
The majority of dolphins exhibit fusion-fission societies. Groups are constantly forming (fusion) and separating (fission). Encounters between dolphins can number in the thousands! This type of social group is rather unstable: a gathering can last from a few minutes to several days.
In Atlantic white-sided dolphins, which can be observed in the Gulf of St. Lawrence, each individual is part of a small group of individuals with which it associates over the long term. They are usually members of the same family. Each individual is also part of an enormous secondary group that is formed and unformed according to their needs.
Compared to the dolphin system, matriarchal groups in sperm whales and killer whales are much more stable. Several generations of related females form the core of the group. They are accompanied by their offspring. In sperm whales, these family groups constitute vocal clans that can comprise thousands of whales. Sperm whales of the same clan share the same vocal patterns that are believed to be acquired through cultural transmission. One clan may live in close proximity to another, but they do not associate with each other.
Females spend their entire lives with their family group. As for bulls, they leave the group before reaching sexual maturity and form temporary groups of males or remain alone.
Long-term social groups like these have certain cognitive benefits. In Hudson Bay, researchers have found that long-term social connections facilitate the learning of complex behaviours such as long-distance migration in belugas.
Last updated: July 2019
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