Researchers from University of Washington (UW) finds that as Arctic sea ice takes longer to freeze up each fall due to climate change, a population of belugas mirrors that timing and delays its migration south by up to one month. In contrast, a different beluga population, also in Alaska, that migrates and feeds in the same areas does not appear to have changed its migration timing with changes in sea ice, researchers said.

“The biggest take—home message is that belugas can respond relatively quickly to their changing environment, yet we can not expect a uniform response across all beluga populations,” said lead author Donna Hauser, from UW. Two genetically distinct beluga populations spend winters in the Bering Sea, then swim north in the early summer as sea ice melts and open water allows them passage into the Beaufort and Chukchi seas.

There they feast all summer on fish and invertebrates before travelling back south in the fall.

The Chukchi beluga population’s response to follow sea ice timing and delay migration likely means the whales are opportunistically feeding later into the fall. On one hand, the whales might be gaining valuable food resources, but they also risk getting blocked from their migration path south if the ice quickly freezes up and catches them off guard.

In contrast, the Beaufort beluga population’s apparent indifference to sea ice timing is surprising, Hauser said. Perhaps the Beaufort whales have a tradition of feeding elsewhere that requires they move away earlier in the fall, regardless of sea ice characteristics, she said.

Researchers, however, note that when they do see changes, they are happening quickly — within a 10—year span for whales that often live to be over 60 years old.