Genetic Analysis Confirms Polygynandrous Mating in Bristol Bay Belugas

A recent scientific investigation has detailed a complex and flexible reproductive strategy utilized by a geographically distinct population of white beluga whales inhabiting Alaska's Bristol Bay. This finding confirms the species engages in polygynandry, a mating system where both male and female individuals associate and reproduce with multiple partners over extended periods.

This reproductive architecture was established through an intensive, 13-year genetic analysis involving the meticulous sampling of 623 belugas, which constitute approximately 2,000 individuals in the local stock. The data confirmed that mating success is distributed across several partners rather than concentrated in a few dominant pairings. This observed pattern of 'mate switching' functions as a critical mechanism to mitigate the risks of inbreeding that often challenge small, isolated populations.

Researchers suggest that the belugas' notably long lifespan contributes to the viability of this multi-partner approach, allowing for repeated partner assessment across many years. Beluga whales, *Delphinapterus leucas*, are known for their high sociality and complex vocalizations, factors that may facilitate the coordination required for such a system. The Bristol Bay population is recognized as genetically distinct from other North American beluga groups, making the preservation of its genetic health a significant conservation focus for regional marine mammal agencies.

From a female's perspective, alternating mates serves as an effective method for managing reproductive uncertainty, primarily by avoiding exclusive pairing with males who may possess lower genetic quality or be closely related. This dynamic offers a nuanced pathway to adaptive evolution within the changing marine environment, contrasting with strictly monogamous or polygynous systems.

The implications for conservation science are substantial, as this flexible mating behavior suggests an inherent biological mechanism bolstering the resilience of this vulnerable whale stock against potential genetic erosion. Genetic diversity is a primary predictor of a population's ability to adapt to stressors such as shifting prey availability, increasing ocean noise, or changes in sea ice extent within the Bering Sea ecosystem. The continued monitoring of these belugas remains essential to track how this behavioral flexibility interacts with ongoing environmental shifts in their habitat.