- Research has found that some bowhead whales in the Bering–Chukchi–Beaufort (BCB) population are no longer migrating to the northwestern Bering Sea in the winter but remain in the Canadian Beaufort Sea.
- These migratory shifts are occurring as sea ice declines in the region due to climate change.
- These changes could mean that bowhead whales become more susceptible to ship strikes, underwater noise, and entanglements, and that Indigenous communities may not be able to rely on bowhead whales for nutrition and cultural subsistence.
- However, this bowhead population is currently not threatened, and these changes may not be fully impacting Indigenous communities yet.
A population of bowhead whales living in the western Arctic has long followed the same migration patterns. But new research suggests that climate change and the subsequent melting of sea ice are altering their movements, raising concerns about the future impacts on these whales and the Indigenous populations reliant on them for nutrition and cultural subsistence.
Researchers used acoustic data, as well as traditional knowledge, aerial surveys and satellite tagging, to examine the shifting distribution and movement of the Bering–Chukchi–Beaufort (BCB) population of the bowhead whale (Balaena mysticetus). These whales typically spend the winter in the northwestern Bering Sea, the northern span of the Pacific Ocean, between Alaska and Russia. They then move northward through the Bering Strait from April and May to reach the Chukchi and western Beaufort seas in the Arctic. From there, they shift toward the east to spend the summer in the Canadian Beaufort Sea. From August to October, they usually move westward toward the Chukotka Peninsula in Russia before eventually returning to the northwestern Bering Sea for the following winter.
But now, these patterns may be shifting.
Drawing on acoustic data from whale songs and non-song calls, the study found that some bowhead whales from the BCB populations were no longer returning to the northwestern Bering Sea as usual. Instead, they remained in the Canadian Beaufort Sea over the winter.
“That’s a huge shift in the winter habitat for these whales,” study lead author Angela Szesciorka, a researcher at the Marine Mammal Institute at the University of Oregon, told Mongabay. “In terms of how concerned we should be, it remains to be seen. The Arctic is changing pretty rapidly, and we’re starting to see these changes. But we don’t quite yet know the broader impacts.”
While the impacts have yet to be fully revealed, the authors suggest that sea ice decline could lead to more vessel traffic and fishing activity in this part of the Arctic that could affect the whales with ship strikes, underwater noise, and entanglements. It’s also possible that the whales’ shifting migration patterns could impact Indigenous communities who depend on the whales. On the other hand, the study noted that this delayed winter migration might give the whales better access to nutrient-rich foods and decrease their chances of being hunted by killer whales (Orcinus orca).
Besides the BCB population of the bowhead whale, there are three other populations: the Eastern Canadian–Western Greenland (ECWG) stock, the East Greenland–Svalbard–Barents Sea (EGSB) stock, and the small and genetically distinct Okhotsk Sea (OKH) stock. The global wildlife conservation authority the IUCN classifies the bowhead whale in general as a species of “least concern,” but it considers the EGSB and OKH subpopulations endangered.
Henry Huntington, an independent researcher focused on Arctic Ocean conservation, who was not involved in the study, said it was surprising that the bowhead whales stayed in the Beaufort Sea over the winter, an area usually packed with ice at that time of year.
“We know bowheads are very good at finding their way in the ice, but the idea that they might be spending the whole winter there is pretty shocking to me,” Huntington told Mongabay. “I guess we knew that was possible, but now that we’re seeing it … yikes.”
Huntington said he doesn’t believe the bowhead whales’ shifting migration patterns are currently having a significant impact on most Indigenous communities but acknowledged this could change in the future.
“I think the place of biggest concern would probably be at the southern end of the range,” he said. “So in the case of Alaska, we’re talking about St. Lawrence Island in the northern Bering Sea. The previous pattern of understanding had been that the majority of the whales went south of St. Lawrence Island in the wintertime, so [they] came past in the fall, went past again in the spring, giving people two chances to go after the whales. With some of the recent findings … a lot of the whales are not going that far south.”
Szesciorka said that while the study revealed that sea ice decline was affecting migrations, the BCB bowhead population was doing well, with numbers “believed to be higher than they were pre-commercial whaling.”
“There’s a good number of them, and the hunters taking them for subsistence are also very successful … so it’s not all doom and gloom,” Szesciorka said. “We’re trying to understand how things are changing, but it doesn’t necessarily mean it’s all for the worse.”
Elizabeth Claire Alberts is a senior staff writer for Mongabay. Follow her on Twitter @ECAlberts.
Banner image: A bowhead mother and calf in the Arctic Ocean. Image by NOAA / National Ocean Service via Flickr.
Audio: Bowhead whales in the Arctic sing hundreds of complex songs
Citation:
Szesciorka, A. R., & Stafford, K. M. (2023). Sea ice directs changes in bowhead whale phenology through the Bering Strait. Movement Ecology, 11(1). doi:10.1186/s40462-023-00374-5