Humpback whale survival at risk in North Pacific due to extreme heat waves

The effects of climate change are seriously threatening the survival of humpback whales in the North Pacific

by Lorenzo Ciotti
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Humpback whale survival at risk in North Pacific due to extreme heat waves
© Mario Tama / Staff Getty Images

The effects of climate change are seriously threatening the survival of humpback whales in the North Pacific.

According to a study published in the journal Royal Society Open Science, between 2012 and 2021, the number of humpback whales in this area decreased by 20%, from 33,000 individuals to just over 26,600. This would be due to the progressive increase in anomalous heat waves.

According to the authors of the study, the future of the species no longer seems so certain.

Ted Cheeseman, a whale biologist and doctoral candidate at Australia's Southern Cross University, said around 7,000 whales died mostly from starvation.

“It's not just whale food that has declined. A warmer ocean produces less food, particularly due to the decline or migration of phytoplankton, the basis of the entire ocean food chain. It's a much stronger signal than we know we waited," he told.

From 2014 to 2016, the strongest and longest marine heat wave on record devastated the northeast Pacific, with temperature anomalies sometimes exceeding 3-6°C, altering the marine ecosystem and the availability of prey for the large cetaceans.

Humpback whale
Humpback whale© Sean Gallup / Staff Getty Images Sport
 

About humpback whales

Humpback whales are widespread in waters all over the world, with the exception of some areas near the equator, in the high Arctic and in some closed seas. Their winter breeding grounds are located around the equator, while their summer feeding grounds are located in colder waters, even near the polar ice caps. Humpback whales undertake large-scale migrations between feeding and breeding grounds, often crossing the open ocean. Some specimens have traveled up to 8,000 kilometers in one direction.

In the North Atlantic there are two distinct wintering populations, one in the West Indies, between Cuba and northern Venezuela, and the other in the waters of Cape Verde and northwestern Africa. During the summer, West Indian humpback whales congregate off New England, eastern Canada, and western Greenland, while the

Cape Verde population congregates around Iceland and Norway.

The North Pacific hosts at least four breeding populations: off the coast of Mexico (in an area that includes Baja California and the Revillagigedo Islands), in Central America, in Hawaii and in the area between Okinawa and the Philippines. The Mexican population feeds between the Aleutian Islands and California, particularly in the Bering Sea, the northern and western Gulf of Alaska, between southern British Columbia and northern Washington, and between Oregon and California.

During the summer, Central American humpback whales are only encountered off Oregon and California. In contrast, Hawaiian humpback whales have a very extensive feeding ground, but most of them head to southeastern Alaska and northern British Columbia.