In the icy waters of Alaska’s Bristol Bay, a small and largely isolated population of beluga whales is quietly rewriting what scientists thought they knew about Arctic cetaceans. New research has revealed that these elusive white whales rely on a surprisingly flexible mating strategy – one that may help safeguard their genetic future in a changing ocean.

Belugas (Delphinapterus leucas) live in environments that are notoriously difficult to study. Ice cover, remote habitats, and turbid waters have long limited scientists’ ability to observe their social lives, leaving major gaps in understanding how belugas choose mates or raise their young.

Now however, a rare long-term study is offering unprecedented insight into the private lives of one of the Arctic’s most enigmatic species.

Led by researchers from Florida Atlantic University’s Harbor Branch Oceanographic Institute, the study is the first to uncover how wild beluga whales mate, who fathers which calves, and how these strategies shape genetic diversity in a small, isolated population.

Over 13 years, researchers – in collaboration with the Alaska Department of Fish and Game and the North Slope Borough Department of Wildlife Management – collected genetic samples from 623 beluga whales in Bristol Bay, an area home to roughly 2,000 individuals. With little evidence of movement between this and other beluga populations, the bay provided a rare opportunity to study a distinct group over time.

Alongside genetic data, scientists recorded social groupings and age structure, allowing them to reconstruct patterns of reproduction across multiple breeding seasons.

Because belugas are exceptionally long-lived – potentially surviving for many decades – the team focused on short-term mating strategies rather than lifetime reproductive success. They set out to determine whether belugas were polygynous, polyandrous, or something more complex.

Published in Frontiers in Marine Science, the findings challenge long-standing assumptions. Rather than a system dominated by a few competitive males, Bristol Bay belugas practice something called polygynandrous mating strategy, in which both males and females mate with multiple partners over several years.

As a result, reproductive success is moderately distributed across the population, producing many half-siblings and relatively few full siblings – a pattern that helps limit inbreeding and maintain genetic diversity despite isolation.

“What makes this study so thrilling is that it upends our long-standing assumptions about this Arctic species,” said Greg O’Corry-Crowe, Ph.D., senior author, a research professor of Wildlife Evolution and Behavior at FAU Harbor Branch and a National Geographic Explorer.

“Because males are much larger than females and appear to spend little time associating with mothers and calves, scientists believed belugas were likely to be highly polygynous, where males spend a lot of time competing for mates and only a few dominant males fathering most of the calves. Our findings tell a very different story.

“In the short term, males are only moderately polygynous. One explanation we think lies in their incredible longevity – belugas can live perhaps 100 years or more. Rather than competing intensely in a single season, males appear to play the long game, spreading their reproductive efforts over many years. It appears to be a ‘take your time, there’s plenty of fish in the sea’ strategy.”

Females, too, play an active role. Rather than mating with a single partner, females frequently switch mates between breeding seasons – a strategy that may reduce reproductive risk and increase the likelihood of producing healthy, genetically diverse offspring.

“It’s a striking reminder that female choice can be just as influential in shaping reproductive success as the often-highlighted battles of male-male competition,” said O’Corry-Crowe. “Such strategies highlight the subtle, yet powerful ways in which females exert control over the next generation, shaping the evolutionary trajectory of the species.”

The study found no clear difference between younger and older adults in terms of how many had calves at any given time. However, older mothers had more surviving offspring, suggesting that experience, condition, and mate choice contribute to long-term success. Most adults produced relatively few calves at once, reflecting slow reproduction and shared reproductive opportunities.

These findings have significant implications for conservation. When reproduction is spread across many individuals, populations are better buffered against genetic erosion, inbreeding, and reduced adaptability – risks that often threaten small or isolated groups.

“If only a few males father most calves, the effective population size becomes much smaller than the number of whales actually present,” said O’Corry-Crowe. “This loss of genetic diversity increases the risk of inbreeding and reduces the population’s ability to adapt to environmental change.

“Frequent mate switching combined with low reproductive ‘skew’ and possibly the active avoidance of mating with close relatives, may be effective strategies to maintaining the genetic health of relatively small populations.”

The research was carried out in close partnership with Indigenous communities in Bristol Bay, whose stewardship and knowledge were integral to the project.

“We cannot afford to be complacent. Small populations still face the dangers of genetic erosion. But we can be optimistic that beluga whale mating strategies provide evidence of nature’s resilience and offers hope for those working to save and recover small populations of any species,” said O’Corry-Crowe.

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