The unexpected appearance of whale carcasses along the coast has been drawing attention. In March, a dead whale was discovered floating in San Francisco Bay, with seagulls gathered around like carrion birds. The following month, a whale washed ashore in Oregon, its body blending with the waves. In the same period, a young whale was found dead, entangled in driftwood in a river in Washington State, far from the sea.
By mid-August, this year had seen 187 gray whale deaths along the West Coast, stretching from Mexico to Alaska. Scientists are urgently investigating these incidents, aiming to prevent more fatalities in a species that has been declining, with gray whale numbers dropping by 35 percent from 2020 to 2025.
Steven Swartz, co-director of the Gray Whale Research in Mexico program, describes the situation as a “complete decline [and] a collapse of reproduction.” The dead whales found along the coast provide clues to the causes: many of them are severely undernourished, resembling “a bag of bones,” according to one scientist.
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This situation marks a tragic turn for a whale species that was once a conservation triumph. After being nearly wiped out by 19th-century whaling, the eastern North Pacific gray whale population had rebounded to about 20,000 by 1994, leading to their removal from the U.S. Endangered Species List. By 2016, the population had grown to approximately 27,000. However, by 2025, their numbers had dwindled to around 13,000 due to numerous strandings along the West Coast.
Researchers are working to unravel the reasons behind the increasing whale deaths by examining the stranded bodies for clues.
From Rebound to Population Plummet
Gray whales, recognized by their mottled skin, dorsal hump, pointed fins, and downward-facing mouths, can grow up to 49 feet long and weigh as much as 90,000 pounds. They undertake one of the longest mammal migrations, covering roughly 10,000 miles annually between Mexico and the Arctic. As they feed, these whales play a crucial role in the ecosystem by stirring nutrients on the ocean floor.
The strange occurrences of whale strandings intensified in December 2018. By 2019, the National Oceanic and Atmospheric Administration (NOAA) had declared an unusual mortality event, prompting an international investigation. Scientists conducted thorough examinations of the dead whales, measuring their bodies, checking for signs of starvation or injury, and analyzing their blubber and organs. Findings indicated that malnutrition was a common cause of death, with some deaths resulting from collisions with boats.
Thus, the whales were mostly dying due to food scarcity or boat strikes.
Although the unusual mortality event was declared over in 2023 as strandings decreased, gray whale deaths remain a concern. John Calambokidis from the Cascadia Research Collective notes that the situation has grown “more alarming.” Despite a slight uptick in population to 18,000, Aimée Lang from the NOAA’s Southwest Fisheries Science Center states that the overall decline continues.
Further evidence suggests that starvation is a key factor in these deaths, linked to changes in the Arctic Ocean’s environment.
How Melting Sea Ice Is Starving Whales
Gray whales primarily feed on the ocean floor, consuming sediment and invertebrates. They trap tiny amphipods, filtering the sediment through baleen plates. This feeding method is closely connected to Arctic sea ice and the algae that grow underneath it.
When algae die, they sink to the seabed, nourishing the crustaceans that gray whales eat. However, the rapid melting of Arctic sea ice due to rising temperatures disrupts this food chain.
Amanda Montañez; Source: National Oceanic and Atmospheric Administration (data)
A study published late last year in the ICES Journal of Marine Science examined decades of data on gray whale populations and Arctic crustacean biomass. The study, co-authored by Joshua Stewart from Oregon State University’s Marine Mammal Institute, found that the health of whales and crustaceans are closely linked. While gray whale populations have fluctuated in the past, Stewart notes, “We’re not seeing signs of the population quickly bouncing back like we did previously.” The ecosystem is no longer able to sustain the number of gray whales it once did, resulting in starvation.
Swartz explains that whales are depleting their energy reserves during migration and dying. He has observed an increase in underweight gray whales returning to their breeding grounds in San Ignacio Lagoon, Baja. There is also a decline in calf births. Lang, who monitors mothers and calves migrating along the California coast, reports that only 17 pairs were counted last year, with an estimated 85 calves born in 2025—a stark contrast to the 1,600 calves born in 2014.
Sign of Hope
Despite the bleak situation, there is hope for gray whales. Lang suggests that they could adapt to changing Arctic conditions by finding food in new areas. She notes that they’ve already shown “pretty amazing behavioral flexibility.”
Evidence indicates some gray whales are altering their behavior. A group known as the Sounders diverges from their northward route to feed in Puget Sound, while the Pacific Coast Feeding Group avoids the Arctic, feeding between northern California and British Columbia.
More whales seem to be adopting these alternative routes. Since 2018, gray whales have been spotted more often in San Francisco Bay, likely searching for food. However, the Bay’s heavy marine traffic poses a danger: at least 18 percent of the whales that entered between 2018 and 2025 died there, according to a recent Frontiers in Marine Science study; many were struck by ships. A new system using AI and thermal cameras is being tested to help ships avoid collisions with whales.
These solutions, however, do not tackle the main threat to gray whales. “The challenge with this case is that the lever we have to pull is slowing or reversing climate change,” Stewart states. “It’s something we know we need to do, but we haven’t done it.”
As gray whales start their southward migration with the change of seasons, scientists will closely monitor their numbers and health upon their return.
“The big question in all our minds is just, where’s the bottom?” Stewart wonders. “I hope they turn around soon.”
