Beluga whales (Delphinapterus leucas) have social systems to rival our own, according to new research led by marine biologists from the Harbor Branch Oceanographic Institute at Florida Atlantic University.
O’Corry-Crowe et al analyzed the relationship between group behaviors, group type, group dynamics, and kinship of beluga whales in 10 locations across the Arctic. Image credit: Lisa Barry / NOAA / NMFS / AFSC / MML.
The beluga is a species of toothed whale that lives in Arctic and subartic waters and occupies a wide range of habitats from shallow estuaries and embayments to deep glacial fjords and open pelagic habitats.
These creatures are one of two members of the family Monodontidae, along with the narwhal, and the only member of the genus Delphinapterus.
Also known as the white whales or the sea canaries, they are distinctive for their white color and sophisticated vocal repertoires.
At birth, belugas are dark gray to brownish gray. They whiten increasingly as they age, reaching the pure white stage between 5 and 12 years of age.
They have a small bulbous head with only a very short beak, no dorsal fin, small rounded flippers, and flukes that often have a convex trailing edge.
Adult belugas are less than 5.5 m (18 feet), and large animals may weigh up to 1.6 metric tons. Calves average about 1.6 m (5.2 feet) at birth.
Belugas exhibit a wide range of grouping patterns from small groups of 2-10 individuals to large herds of 2,000 or more.
Some beluga populations undertake long annual migrations, returning each summer to traditional summering grounds where they congregate in coastal waters to feed, raise their young, and undergo an annual molt.
Like killer whales (Orcinus orca) and African elephants (Loxodonta africana), belugas were thought to form social bonds around females that primarily comprise closely related individuals from the same maternal lineage. However, this hypothesis had not been formally tested.
“Our research will improve our understanding of why some species are social, how individuals learn from group members and how animal cultures emerge,” said lead author Dr. Greg O’Corry-Crowe, a researcher in the Harbor Branch Oceanographic Institute at Florida Atlantic University.
For the study, Dr. O’Corry-Crowe and colleagues used field observations, mtDNA profiling, and multi-locus genotyping of beluga whales to address fundamental questions about beluga group structure, and patterns of kinship and behavior.
The scientists conducted the study at 10 locations, in different habitats, across the species’ range.
They found that belugas formed a limited number of group types, from mother-calf dyads to adult male groups, and from mixed-age groups to large herds. These same group types were consistently observed across population and habitats.
Furthermore, certain behaviors were associated with group type, and group membership was found to often be dynamic.
Given their long lifespan (approximately 70 years) and tendency to remain within their natal community, these results reveal that beluga whales may form long-term affiliations with unrelated as well as related individuals.
“It also has implications for traditional explanations based on matrilineal care for a very rare life-history trait in nature, menopause, which has only been documented in a handful of mammals, including beluga whales and humans,” Dr. O’Corry-Crowe said.
Beluga whale groupings beyond mother-calf dyads were not usually organized around close maternal relatives.
The smaller social groups, as well as the larger herds, routinely comprised multiple matrilines.
Even where group members shared the same mtDNA lineage, microsatellite analysis often revealed that they were not closely related, and many genealogical links among group members involved paternal rather than maternal relatives.
“This new understanding of why individuals may form social groups, even with non-relatives, will hopefully promote new research on what constitutes species resilience and how species like the beluga whale can respond to emerging threats including climate change,” Dr. O’Corry-Crowe said.
The findings were published in the journal Scientific Reports.
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G. O’Corry-Crowe et al. 2020. Group structure and kinship in beluga whale societies. Sci Rep 10, 11462; doi: 10.1038/s41598-020-67314-w
