Grey Whale Death Toll in Mexico Reaches Record Levels in 2025
Scientists cite Arctic disruption and La Niña among leading causes
As of mid-April 2025, a total of 84 grey whales have been found dead in Mexican waters — a troubling number for a species that migrates more than 9,000 kilometers from Alaska each year to breed and give birth along the coasts of Baja California Sur.
This figure surpasses the 83 whale deaths recorded in 2019 and nears the 2020 peak of 88 during the height of the Unusual Mortality Event (UME), which led to the loss of 40% of the Eastern North Pacific grey whale population — approximately 690 individuals.
Dr. Jorge Urbán Ramírez, lead researcher of the Marine Mammal Research Program (PRIMMA-UABCS) at the Autonomous University of Baja California Sur (UABCS), confirmed that the 2025 death toll could still rise, as several grey whales remain in the Gulf of California, including waters off La Paz, Cabo San Lucas, and nearby coastal areas, as the whale watching season comes to a close.
In a recent meeting with scientists who have monitored the UME from 2019 to 2023, researchers reiterated that the leading cause of this persistent mortality trend stems from oceanographic disruptions in the Arctic, particularly in the Bering Sea where changes in sea ice coverage have drastically impacted the whales’ feeding grounds.
These environmental changes, believed to be driven by climate change, have led to higher sea temperatures in the whales’ traditional foraging areas, resulting in a decline in prey availability. As a consequence, many whales arrive in Baja’s breeding lagoons malnourished and weakened, further contributing to lower reproductive success.
Adding complexity to the situation is the atypical distribution of whales observed this season. Cold-water upwelling caused by La Niña has shifted the whales’ presence southward, away from their traditional breeding sanctuaries such as Laguna San Ignacio, Ojo de Liebre, and the Bahía Magdalena complex. This forced the whales to expend more energy migrating farther in search of suitable temperatures — a critical stressor during an already vulnerable life stage.
Researchers warn that the combination of Arctic ecosystem instability, climate variability, and increased migration demands poses a continued threat to the recovery of the grey whale population.
This ongoing crisis underscores the need for greater international research cooperation and conservation action to understand and mitigate the environmental factors impacting these iconic marine mammals.
Source: PRIMMA-UABCS
