The annual return of beluga whales, Delphinapterus leucas, to traditional seasonal locations across the Arctic may involve migratory culture, while the convergence of discrete summering aggregations on common wintering grounds may facilitate outbreeding. Natal philopatry and cultural inheritance, however, has been difficult to assess as earlier studies were of too short a duration, while genetic analyses of breeding patterns, especially across the beluga’s Pacific range, have been hampered by inadequate sampling and sparse information on wintering areas. Using a much expanded sample and genetic marker set comprising 1,647 whales, spanning more than two decades and encompassing all major coastal summering aggregations in the Pacific Ocean, we found evolutionary-level divergence among three geographic regions: the Gulf of Alaska, the Bering-Chukchi-Beaufort Seas, and the Sea of Okhotsk (Φst = 0.11–0.32, Rst = 0.09–0.13), and likely demographic independence of (Fst-mtDNA = 0.02–0.66), and in many cases limited gene flow (Fst-nDNA = 0.0–0.02; K = 5–6) among, summering groups within regions. Assignment tests identified few immigrants within summering aggregations, linked migrating groups to specific summering areas, and found that some migratory corridors comprise whales from multiple subpopulations (PBAYES = 0.31:0.69). Further, dispersal is male-biased and substantial numbers of closely related whales congregate together at coastal summering areas. Stable patterns of heterogeneity between areas and consistently high proportions (~20%) of close kin (including parent-offspring) sampled up to 20 years apart within areas (G = 0.2–2.9, p>0.5) is the first direct evidence of natal philopatry to migration destinations in belugas. Using recent satellite telemetry findings on belugas we found that the spatial proximity of winter ranges has a greater influence on the degree of both individual and genetic exchange than summer ranges (rwinter-Fst-mtDNA = 0.9, rsummer-Fst-nDNA = 0.1). These findings indicate widespread natal philopatry to summering aggregation and entire migratory circuits, and provide compelling evidence that migratory culture and kinship helps maintain demographically discrete beluga stocks that can overlap in time and space.

Evolutionary explanations for mammalian sociality typically center on inclusive-fitness benefits of associating and cooperating with close kin, or close maternal kin as in some whale societies, including killer and sperm whales. Their matrilineal structure has strongly influenced the thinking about social structure in less well-studied cetaceans, including beluga whales. in a cross-sectional study of group structure and kinship we found that belugas formed a limited number of distinct group types, consistently observed across populations and habitats. certain behaviours were associated with group type, but group membership was often dynamic. MtDNA-microsatellite profiling combined with relatedness and network analysis revealed, contrary to predictions, that most social groupings were not predominantly organized around close maternal relatives. they comprised both kin and non-kin, many group members were paternal rather than maternal relatives, and unrelated adult males often traveled together. the evolutionary mechanisms that shape beluga societies are likely complex; fitness benefits may be achieved through reciprocity, mutualism and kin selection. At the largest scales these societies are communities comprising all ages and both sexes where multiple social learning pathways involving kin and non-kin can foster the emergence of cultures. We explore the implications of these findings for species management and the evolution of menopause. Interpreting gregarious behaviour in terms of cooperative strategies that maximize individual fitness, Hamilton 1 developed the theory of kin selection. This theory uses the concept of inclusive fitness to explain the evolution of social organization and cooperation where individuals indirectly enhance their fitness through positive effects on the reproduction of relatives. However, individuals can also derive benefits from associations with unrelated individuals where cooperation is conditional on the behaviour of the companion (i.e., reciprocity 2,3), always yields the highest benefit (i.e., mutualism 4,5) or results in shared fitness advantages from helping increase group size (i.e., group augmentation 6,7) which, for example, could lead to more effective group defense. In fluid aggregations, such as herds or flocks, benefits to the individual alone (e.g., reducing personal predation risk at the expense of other group members) may drive the tendency to associate with conspecifics 8,9. Thus, resolving the genetic relationships among group members is central to understanding the advantages of group living, the emergence of cooperative behaviour, and the evolution of social organization. The recent re-emergence of arguments for group selection theory, where kinship plays a minor role in social evolution 10,11 , and the debate these arguments have elicited 12 , as well as the growing evidence for culture in non-primate species 13-15 (defined as the acquisition or inheritance of knowledge or behaviours from conspecifics through social learning 13), has further heightened the intere...

The Bristol Bay stock of beluga whales (Delphinapterus leucas) is genetically distinct and resides in Bristol Bay year-round. We estimated the abundance of this population using genetic mark-recapture, whereby genetic markers from skin biopsies, collected between 2002 and 2011, were used to identify individuals. We identified 516 individual belugas in two inner bays, 468 from Kvichak Bay and 48 from Nushagak Bay, and recaptured 75 belugas in separate years. Using a POPAN Jolly-Seber model, abundance was estimated at 1,928 belugas (95% CI = 1,611-2,337), not including calves, which were not sampled. Most belugas were sampled in Kvichak Bay at a time when belugas are also known to occur in Nushagak Bay. The pattern of genetic recaptures and data from belugas with satellite transmitters suggested that belugas in the two bays regularly mix. Hence, the estimate of abundance likely applies to all belugas within Bristol Bay. Simulations suggested that POPAN estimates of abundance are robust to most forms of emigration, but that emigration causes negative bias in both capture and survival probabilities. Because it is likely that some belugas do not enter the sampling area during sampling, our estimate of abundance is best considered a minimum population size.Beluga whales (Delphinapterus leucas) are small cetaceans (≤5.5 m), that live in seasonally ice covered waters in arctic and subarctic regions. Populations are typically named for where they summer and, in Alaskan waters, five populations are commonly recognized by their summer ranges: Cook Inlet, Bristol Bay, eastern Bering Sea, eastern Chukchi Sea, and Beaufort Sea (Frost and Lowry 1990; O'Corry-Crowe et al.