Elizabeth Alter (Asst. Prof., York, Biology) was the lead author on a study by a distinguished team of American and Canadian scientists: “Gene flow on ice: The role of sea ice and whaling in shaping Holarctic genetic diversity and population differentiation in bowhead whales (Balaena mysticetus),” which appeared online in the new Wiley open access journal Ecology and Evolution on October 18. The study was picked up by Juliet Eilperin of the Washington Post in her October 18 article “Bowhead whales lost genetic diversity, study shows.” Alter earned her Ph.D. in biological sciences from Stanford University; her M.A. in environmental sciences, policy, and management from University of California–Berkeley; and her B.A. in organismal biology and anthropology from Yale University.
Alter’s coauthors on the bowhead whale study include scientists from the Wildlife Conservation Society in New York; the American Museum of Natural History; Fisheries and Oceans Canada, Winnipeg; Department of Anthropology and Archaeology, Memorial University of Newfoundland; Southwest Fisheries Science Center, California; Greenland Institute of Natural Resources; Applied Physics Laboratory, Polar Science Center, University of Washington; and the Department of Ecology and Evolutionary Biology, Yale University.
Reaching up to sixty-five feet in length and up to one hundred tons in weight, the bowhead whale is a baleen whale that lives in Arctic and sub-Arctic waters. The enormous arched head, which gives it its name, can break through ice up to two feet thick. The species was widely hunted for centuries by commercial whalers, who valued its long baleen, which was used in corsets and other items, and its thick blubber, the thickest of any species of whale. The bowhead whale may also be among the most long-lived mammal species. In 2007, aboriginal whalers on the Alaskan coast landed a whale carrying a valuable clue about the animal’s probable age: a harpoon point manufactured in the 1890s was imbedded in the whale’s blubber, indicating the animal may have survived an encounter with whalers more than a century before.
“Our study represents the first genetic analysis of bowheads across their entire range,” says Alter, “and also illustrates the value of ancient DNA in answering questions about the impact of changing climate and human exploitation on genetic diversity in bowhead whales.” The study employed hundreds of samples, including DNA gathered from whales over the past twenty years as well as genetic material extracted from ancient vessels, toys, and housing material made from baleen and bone that had been preserved in pre-European settlements in the Canadian Arctic.
The genetic analysis revealed differences between ancient and modern population diversity, including the recent disappearance of unique maternal lineages over the past five hundred years, the possible result of habitat loss during the Little Ice Age (a period of climatic cooling that occurred between the sixteenth and nineteenth centuries) and/or extensive whaling in the region.
Another finding of the study: the frozen—and seemingly impassable—inlets and straits separating Atlantic and Pacific populations appear to be little obstacle to the ice-savvy bowheads. The team found the whale populations in the two regions to be so related that individual whales must have been able to make the journey across the ice-choked Arctic, although the finer details on the directions whales traveled are still uncertain.
“The assumption that Arctic sea ice has separated bowhead whale populations over the past few thousand years is contradicted by the genetic analysis, which indicates that significant migration between Atlantic and Pacific populations has recently taken place,” said Dr. Howard Rosenbaum, director of the Wildlife Conservation Society’s Ocean Giants Program and a coauthor on the study. “The finding reveals much about the abilities of bowheads to find navigable routes through sea ice and helps illuminate hidden connections between populations.”
The authors point out that understanding the effects of shifting sea ice conditions and commercial whaling is important for future management decisions for the bowhead whale, particularly in light of the disappearance of sea ice due to climate change and increased shipping in the Arctic environment.
The bowhead whale has been protected from commercial whaling by the International Whaling Commission (IWC) since 1946. Currently, limited subsistence whaling by coastal communities on the Bering, Beaufort, and Chukchi Seas is permitted by the IWC. Bowheads are listed on Appendix I of CITES (Convention on International Trade in Endangered Species), a listing that completely prohibits international trade, and are listed as a species of “Least Concern” on the IUCN’s Red List of Threatened Species.