Arctic sea ice loss delays whale migration: study

Sea ice changes in the Arctic may delay the annual migration of some beluga whales in Alaska by up to a month, a new study has found.
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.
"If we are trying to understand how these species are going to respond to climate change, we should expect to see variability in the response across populations and across time. That may complicate our predictions for the future," Hauser said.
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, but researchers do not yet know if that delay is overall beneficial.
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, given that both populations frequent many of the same feeding areas and otherwise appear to have similar life histories.

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.
"This all suggests that beluga whales can respond to their changing Arctic conditions, although all populations will not necessarily respond the same," Hauser 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.
That means migration patterns that are inherited over generations are changing within the lifespans of multiple generations of whales, Hauser said.

The study was published in the journal Global Change Biology.