The ice that once saved bowhead whales is vanishing beneath them

The Bering-Chukchi-Beaufort group is by far the largest, with more than 17,000 whales. They migrate through the Bering Strait between Canada and Russia in spring, heading about 1,500 kilometers north, and come back south in the fall. 

The East Canada-West Greenland group now has about 11,000 whales. As the name suggests, this group travels more than 2,700 kilometers to the far north of Eastern Canada in the summer and back in the fall, straying as far east as Greenland. The last two populations have only a few hundred whales each.

Bowhead whales follow sea ice, moving north as the ice begins to thin and crack. The whales are following the opening ice in search food. 

When hunting was at its peak, some the whales found refuge behind areas of thick sea ice where whaling ships couldn’t go, says Nicholas Freymueller, an extinction biologist at Adelaide University in Australia. Freymueller and his colleagues reconstructed the whaling results from more than 700 whaling trips (tracking 72,000 days of whaling) to find out exactly where whales were killed. 

The whale populations in Eastern Canada, and off the coast of Alaska in the Bering Sea may have bounced back because they had more refuges avainable, says Freymueller. But the East Greenland- Svalbard- Barents group was hunted for centuries longer than others, while the Okhotsk group had little sea ice to hide behind when whaling ships came calling. That might be why their populations remain so small, he explains.