Hundreds of gray whales have starved to death along the Pacific coastline in recent years, and federal data confirms the population has not bounced back. Between 2019 and 2023, 690 gray whales were found dead across the United States, Mexico, and Canada in what the federal government designated an Unusual Mortality Event. Necropsies performed on a subset of those animals pointed to malnutrition as a common cause of death. Now, the latest population surveys show that abundance and calf production remain depressed, raising hard questions about whether the food supply in Arctic feeding grounds can still sustain the Eastern North Pacific herd.
Why starving gray whales still wash ashore after the mass die-off ended
The federal government formally closed the 2019–2023 gray whale Unusual Mortality Event, but the crisis it described has not resolved. In its official closure announcement, NOAA Fisheries acknowledged that abundance and calf productivity estimates continue to show depressed levels even after the UME period ended. In practical terms, fewer calves are being born, and the adult population keeps shrinking.
The connection between food scarcity and whale deaths is not speculative. During the UME, NOAA documented 347 strandings in the United States, 316 in Mexico, and 27 in Canada. Necropsy findings from a subset of those whales confirmed that starvation, not a single disease outbreak, was killing them. The pattern pointed upstream to the northern Bering and Chukchi seas, where gray whales spend summers gorging on bottom-dwelling amphipods to build the fat reserves they need for a roughly 10,000-mile round-trip migration.
A testable question sits at the center of this story: if reduced prey density in the northern Bering Sea is the dominant driver, then the years with the lowest calf counts should line up with the highest rates of adult emaciation recorded in the stranding network, regardless of total population size. That relationship would separate food-supply failure from a simple population correction. Federal datasets tracking both calf production and body condition exist, but the public record does not yet contain a formal analysis linking those two variables across the full UME timeline.
Necropsy evidence and population counts confirm a food crisis
The strongest evidence comes from two primary federal sources. A peer-reviewed study published in PLOS ONE examined gray whale carcasses recovered from December 2018 through 2021 and found that malnutrition and emaciation were major contributors to death rather than any single infectious agent. That distinction matters because it rules out a viral or bacterial epidemic and focuses attention squarely on the food web. Whales examined during the study showed depleted blubber layers and wasted muscle, consistent with animals that failed to gain enough weight during their Arctic feeding season.
Population-level data reinforces the necropsy findings. NOAA’s Southwest Fisheries Science Center conducted shore-based migration counts off California from December 2024 through February 2025, producing the most recent official abundance estimate for the Eastern North Pacific gray whale population. That technical memorandum provides the clearest snapshot of where the herd stands after years of elevated mortality. The numbers show the population continuing to decline after the downturn that began during the UME, with no clear sign that the herd has returned to pre-2019 levels.
NOAA’s closure report on the UME itself offered the bluntest official language. The agency stated that necropsy findings from a subset of the 690 stranded whales “supported malnutrition as a common cause of death.” Across the full event, the 347 U.S. strandings were spread along the West Coast from Washington to Southern California, with additional concentrations in Baja California lagoons where gray whales calve each winter. The geographic breadth of the die-off suggested that whales were arriving on their southbound migration already too thin to survive, rather than succumbing to localized hazards.
Those findings also help explain why strandings have continued even after the UME’s formal end. If the underlying issue is a chronic shortfall in prey, rather than a one-time shock, then the population can keep losing animals for years as weakened whales fail to complete the migration and reproductive output lags behind adult mortality. The closure of the UME reflects a procedural decision about how NOAA classifies unusual events, not a declaration that the ecological problem has been fixed.
Gaps in Arctic prey data and unresolved calf-count questions
Several pieces of the puzzle are still missing. Direct measurements of amphipod biomass or ocean temperature at primary gray whale feeding sites in the Bering and Chukchi seas do not appear in the publicly available federal reports tied to the UME or the latest abundance estimates. Without that data, researchers can describe the symptoms of food-web failure but cannot quantify how much prey has actually disappeared or map exactly where the shortfall is worst.
Full necropsy reports for the most recent strandings also remain limited. The PLOS ONE synthesis covers carcasses examined through 2021, leaving a gap of several years during which strandings continued. Any shift in causes of death over that later period, such as an increasing role for ship strikes or entanglement, is not yet documented in the same level of detail. That makes it harder to determine whether malnutrition remains the dominant driver or has become one factor among several compounding stresses.
Updated calf-production counts tied to the 2024–2025 abundance survey have not yet been published through NOAA’s gray whale condition and calf production portal, which pairs abundance and reproductive data in a single time series. Until those figures are released, the question of whether low calf output tracks adult starvation rates year by year cannot be answered with public data. Researchers can infer a connection from the combination of low abundance and poor body condition, but a rigorous statistical link between calf counts and emaciation rates remains to be drawn.
What is clear is that the Eastern North Pacific gray whale population entered 2025 in a weakened state. The latest abundance estimate shows a herd smaller than it was before the UME, and the best-available necropsy evidence points to a food supply that has not reliably supported the energetic demands of migration and reproduction. Until scientists can match those population trends to concrete measurements of prey availability in the Arctic, the precise mechanics of the crisis will remain partly unresolved, even as more underweight whales continue to wash ashore.
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*This article was researched with the help of AI, with human editors creating the final content.
