DNA evidence is offering rare insight into the hidden social lives of beluga whales beneath the Arctic ice.
Beluga whales can disappear beneath Arctic sea ice for long stretches, which makes them far tougher to follow than many other whale species. That is why researchers have increasingly turned to genetics as a way to study what they cannot reliably watch.
Using DNA from belugas in Bristol Bay, Alaska, scientists pieced together patterns of reproduction and found that both males and females produce calves with multiple partners over the years, a mixing that could help this small, isolated population stay genetically viable.
“We still know very little about beluga whales, despite their immense popularity,” said Dr Greg O’Corry-Crowe of Florida Atlantic University, lead author of the paper in Frontiers in Marine Science. “The primary reason for this is the difficulty of studying a species that lives beneath the waves in the cold and often frozen north. But this is the challenge that makes discovery, when it happens, more exciting.”
Secrets of the ice
Instead of trying to document elusive mating behavior directly, the team treated DNA like a record of past relationships. Over 13 years, scientists from Florida Atlantic University and the Alaska Department of Fish and Game worked with Alaska Native subsistence hunters from Bristol Bay to collect small tissue samples from 623 whales.
With relatively little baseline knowledge about mating strategies in wild belugas, the researchers leaned on evolutionary theory and key features of beluga biology to frame predictions they could test against the genetic data. One clue is that males are significantly larger than females, while females typically can only have one calf every few years, a combination that often shapes which individuals win reproductive opportunities.
“We predicted that beluga whales had a polygynous mating system where a few of the most competitive and possibly largest males secure most of the matings within a season or even across a few seasons, and that they provide little or no parental care,” said O’Corry-Crowe.
But belugas are not solitary animals, and their social lives complicate that simple picture. They form large groups that regularly split up and recombine, a shifting structure that can repeatedly expose females to new potential mates. For that reason, the scientists also expected that females might mate with many different males across breeding seasons.
Playing the long game?
When the scientists looked at the results, they found that both male and female belugas had calves with different mates over the years. If calves had siblings, they usually only shared one parent. All belugas had a small number of calves, but there was more variation in males’ reproductive success: some males fathered slightly more calves.
“Beluga males were indeed polygynous, but, surprisingly, only moderately so,” said O’Corry-Crowe. “The three-dimensional aquatic environment likely limits a male’s ability to successfully court or corral multiple females. However, a long life may also be key. Belugas can live 90 years, possibly more. Male beluga whales may, therefore, play a long game of securing a few matings each year over a very long reproductive life!
“The female story is just as fascinating. The genetic profiling revealed that female belugas regularly switch mates across breeding seasons, also over a long reproductive life. This could be a bet-hedging strategy to limit the risk of mating with low-quality males.”
Surprising resilience
The scientists also found unexpectedly high genetic diversity and low levels of inbreeding, despite a small population of just 2,000 individuals. Comparing the results to other populations and historical samples from Bristol Bay indicates that this population’s genetic diversity is roughly equivalent to larger populations and has remained stable over time.
“A leading concern for small populations is that they tend to lose genetic diversity faster than large populations and the risks of inbreeding are higher,” explained O’Corry-Crowe. “We expected to find low diversity and high inbreeding, but we found something quite different. The mating system may explain this surprising finding. Frequent mate switching limits the number of highly related offspring in the population. This, in turn, reduces the risk of highly related individuals mating and producing highly inbred offspring. It also minimizes the risk of diversity loss. We cannot afford to be complacent, but we can be optimistic that beluga whale mating strategies provide evidence of nature’s resilience.”
The scientists warn that other populations could behave differently. Sexual dimorphism is comparatively low in Bristol Bay, which may indicate that mating depends less on competition between these males than it does elsewhere.
“To me, the differences in sexual dimorphism among populations of beluga whales could indicate that mating systems also vary, and this is something we are currently working on,” said O’Corry-Crowe. “We also can’t determine if females mate with multiple males within a season using genetics, as a female only produces one calf from one lucky male. But we are working on this, using drones at other locations to determine if we can observe mating behaviors in the wild. More on that soon…”
Reference: “Mating systems, parentage, and reproductive success of beluga whales in Bristol Bay, Alaska” by G. O’Corry-Crowe, L. Quakenbush, T. Ferrer, J. J. Citta and A. Bryan, 18 November 2025, Frontiers in Marine Science.
DOI: 10.3389/fmars.2025.1707758
Funding: Alaska Beluga Whale Committee, Alaska Department of Fish and Game, National Marine Fisheries Service, North Pacific Research Board, NOAA Research, Florida Atlantic University
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