Between 2016 and 2020, the estimated population of eastern North Pacific gray whales plummeted by nearly a quarter, from almost 27,000 individuals to around 20,500. The origins of the decline are so far a mystery. Much of the early research points to climate change, which is rapidly warming the Arctic Ocean and may be reducing the quantity or quality of whales’ food supply. But scientists can’t rule out other factors, including the possibility that the whale population grew too large and is simply correcting itself.
Experts up and down the coast are urgently investigating because these mammals, with their 12,000-mile migrations, are critical barometers of ocean health. Gray whales are known for being a robust, adaptable species. Trouble for them could indicate much bigger problems—including along their feeding grounds on the sea floor, a crucial part of the marine food web and an area that scientists know relatively little about because it's so logistically difficult to study.
“They’re sentinels for what’s going on in the North Pacific ecosystem writ large,” says Sue Moore, a research scientist at the University of Washington who is helping lead NOAA’s probe.