Table 3.

Beluga whale group types, their behavior and likely function, and the degree to which they are kin-based.

	Type of group	Proportion comprised of close kin	Composition	Behaviors and likely function	Original field description	Similar group types and behaviors in the literature
A	Mother–calf dyad	High	Mother–calf pair	All three mother–calf group types engage in behaviors likely related to natal care and possibly shared care of young	Adult–calf dyad	19,21,41
	Mother–calf triad	–	Likely mother with two calves		Triad
B	Mother–calf group	Intermediate	Likely coalescence of mother–calf dyads/triads, not all group members are close relatives		Adult–calf group
C	Juvenile-only group	Low	Calves of multiple ages and different maternal lineages	Behaviors likely indicate play and possibly reciprocal social learning	Juvenile-only group	19,41
D	Adult-male group	Low	Typically, between 2 and 15 whales; multiple maternal lineages	Coordinated behaviors suggestive of socio-sexual dominance, male reproduction	Adults-only group	21,23
E	Mixed-age group	Low	Typically, less than 10 individuals, of both sexes and all ages; multiple maternal lineages	Diverse behaviors that indicate social interaction, likely feeding, and travel	Mixed-age group	23
F	Adult-male herds	Low	> 50 to several hundred individuals; multiple maternal lineages	Diverse behaviors that indicate social interaction, predator avoidance, likely feeding and migration	Adult-only herd	45,46
G	Mixed-age herds	Low	> 50 to low thousands of individuals, of both sexes and all ages; multiple maternal lineages; limited evidence of preferential associations among maternal kin	Diverse behaviors including social interaction, feeding, and migration; dynamic internal grouping patterns	Mixed-age herd	16,45,46

A more detailed summary of beluga whale grouping types can be found in Supplementary Information.