A dead whale washed ashore on the coast of Playas de Rosarito on the afternoon of Monday, May 4. Municipal authorities launched a multi-agency response to investigate the animal’s cause of death.
The city government coordinated with federal, state, and local agencies, including Mexico’s Secretaría de Medio Ambiente (Secretariat of Environment), to manage the scene and begin an investigation. Officials have not yet identified the species or released details about the whale’s size or condition.
Possible Causes Range From Natural Death to Human Impact
Authorities said the investigation will examine several possible causes of death. These include natural causes, a vessel strike, or entanglement in fishing gear. A necropsy is expected to provide more answers, though results may take weeks to complete.
The Rosarito coastline sits along the Pacific migration corridor used by gray whales, which travel between feeding grounds in Alaska and breeding lagoons in Baja California Sur. The typical migration season runs from December through April, and a whale appearing on Rosarito’s shore in early May falls at the tail end of the northward journey back to colder waters.
Gray Whale Deaths a Growing Concern on Pacific Coast
The discovery comes during a period of heightened concern over gray whale mortality along the entire Pacific coast. In April 2025, a 50-foot gray whale washed ashore in Huntington Beach, California, with no visible signs of physical injury. Researchers with the Pacific Marine Mammal Center performed a necropsy and sent samples to a lab for further testing.
Observers who track the annual gray whale migration have reported historically low numbers in recent seasons. The gray whale population, once removed from the U.S. endangered species list in 1994, has experienced periodic die-offs known as Unusual Mortality Events.
Beached whales can temporarily restrict access to sections of shoreline while authorities work to examine and remove the carcass. Rosarito’s beaches draw large crowds of visitors and residents year-round, and officials may cordon off the area near the whale while the investigation continues.
The story was first reported by Zeta Tijuana.