Some bowhead whales are making a comeback. Others aren’t, and the difference may come down to where ships couldn’t go and what those unreachable waters protected.
A new study published in Proceedings of the National Academy of Sciences finds that thick Arctic sea ice once acted as a natural barrier to industrial whaling, limiting how far ships could travel and which habitats they could reach. Some whale populations were partially shielded from the most intense hunting simply because they lived in places that were harder and riskier to access.
Those populations are now recovering the fastest, while others that were more exposed remain far behind.
“Our analysis discovered that bowhead whale populations with ancestors who found refuge in these protective zones, hidden behind hazardous sea ice barriers, are recovering more quickly today,” said senior author Damien Fordham in a press release.
How Industrial Whaling Spread Across the Arctic for Bowheads
Bowhead whales were hunted at an enormous scale before modern conservation existed.
To trace how that pressure unfolded, researchers turned to historical ship logs, reconstructing more than 700 whaling voyages and tens of thousands of days at sea. The records map where fleets traveled and how hunting moved across the Arctic.
Commercial whaling dates back to the 1500s along the coasts of eastern Canada, then spread as European and American fleets joined the hunt. By the late 1700s and 1800s, ships were traveling thousands of kilometers in search of whales, driven by demand for blubber oil used to light homes and power industrial machinery.
At least 250,000 bowhead whales were killed before commercial whaling faded in the early 1900s, with some years seeing more than 2,000 taken across the Arctic.
As whales became harder to find, whalers kept pushing north, moving from the easiest waters into deeper parts of the Arctic and following the edges of sea ice, where whales gathered in large numbers. Within about a century, they had reached nearly every major bowhead habitat.
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How Sea Ice Protected Some Bowhead Whales
By pairing ship records with reconstructed ice conditions, the researchers found that dense ice slowed travel, reduced hunting success, and blocked access altogether. Whalers rarely ventured into areas with heavy ice cover, and when they did, their chances of landing a whale dropped.
Bowhead whales tend to gather along the edges of sea ice, where food is easier to find. These zones drew whalers in, but weren’t always safe to reach.
That mismatch shaped where hunting pressure built up. Waters with moderate ice were heavily hunted, while regions behind thicker ice saw far less activity.
These harder-to-reach zones became de facto refuges, allowing whale populations to hold on while others declined. Some of the largest refuges formed in parts of the Canadian Arctic and near Alaska, while other regions, including the Sea of Okhotsk, had fewer.
Why Some Bowhead Whale Populations Are Recovering Faster
More than a century after commercial whaling ended, bowhead whale populations are recovering at very different rates.
Today, only two of the four populations are clearly rebounding. Those in Alaska and between Canada and West Greenland have increased more than fivefold from their lowest levels. Others, including those near East Greenland and in the Sea of Okhotsk, remain small, numbering in the low hundreds.
Populations with access to ice-protected refuges were never pushed as close to collapse, giving them a stronger base once hunting stopped. In contrast, those who were more exposed faced longer, more intense exploitation, leaving them with a slower path to recovery.
“It underscores the need to consider historical threats dating back centuries when designing recovery plans for species that were pushed to the brink of extinction and remain vulnerable today,” Fordham concluded in the press release.
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