Migratory culture, population structure and stock identity in North Pacific beluga whales (Delphinapterus leucas)

Abstract

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.

Group structure and kinship in beluga whale societies

“…These findings, in concert with the discovery of closely related individuals returning to the same summering location years and even decades apart, are compelling evidence of natal philopatry to migration destinations where the strong mother-calf bond may facilitate the cultural learning of migration routes 40 . However, it must be noted that herds also contain large numbers of unrelated individuals 39,40 and the potential preferential association of matrilines (or even just close kin) beyond mother-calf pairs within these large seasonal aggregations has not been investigated. Furthermore, there is almost no information on the possible role of kinship in smaller groupings.…”

“…On the face of it, beluga whales seemed to fit this model; they form multi-generational groupings 16,21,23 , females have long post-reproductive lifespans 46,62 , and the prolonged period of maternal care seems the likely conduit for social learning and the emergence of migratory culture 40 . Our study did find that close kin, including close maternal kin, regularly interact and associate.…”

“…Several genetic studies have revealed a strong tendency for beluga whales to remain in their natal subpopulation or population [35][36][37][38][39][40] . When viewed with the current study's findings this provides more insight into the social, ecological and demographic scales at which beluga whale societies may be operating.…”

Persistent Mü̈llerian duct syndrome in a beluga whale Delphinapterus leucas

“…The beluga whale taken by a subsistence hunter from Utqiagvik, Alaska, most likely belonged to the Eastern Beaufort stock (O'Corry-Crowe et al 2018). Based on body length and white skin coloration, the male was mature with an estimated age of at least 15 yr (Burns & Seaman 1988).…”

Whale tear glands in the bowhead and the beluga whales: Source and function

“…The beluga, Delphinapterus leucas (Pallas, 1776), used in this study were captured over the summer of 2017 (Table ) in northern Alaska. The belugas from the population that spend the summer season in the eastern Chukchi Sea (O'Corry‐Crowe et al, ) are harvested by subsistence hunters from the village of Point Lay on the Chukchi Sea and samples are collected under a NOAA‐NMFS permit. This harvest is regulated by the Alaska Beluga Whale Committee, and permitted under the U.S. Marine Mammal Protection Act.…”