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Cetacean Strandings and Response

Stranded whales, dolphins and porpoises provide opportunities to learn about these marine mammals that rarely come ashore and contribute to baseline data about the health of our ocean.

Since 1982, The Marine Mammal Center has responded to more than 600 strandings of cetaceans, a classification of marine mammals that includes whales, dolphins and porpoises. These responses include live strandings as well as animals that have washed ashore post-mortem.

The Center is the primary responder for live whale, dolphin and porpoise strandings along 600 miles of the central and northern California coastline, although whale strandings, in particular, are relatively rare. The Center typically responds to five to six whales per year, mostly in the spring months during migration season.

More frequently when a cetacean stranding is reported, the animal has unfortunately already perished. In those cases, the Center works closely with partners in the Marine Mammal Stranding Network that are the primary responders for dead marine mammals. Researchers perform a necropsy on the carcass to determine the cause of death and collect samples that can help further knowledge of marine mammals and their health issues.

When human impacts—such as ship strikes or entanglements—are noted as a cause of injury or death, we use this information to help raise awareness about these issues and effect change. In 2013, changes were made to the mile-wide shipping lanes into San Francisco Bay to reduce traffic in areas whales are known to frequent, thanks to data from The Marine Mammal Center and other members of the Marine Mammal Stranding Network.

Even when a cause of death is unable to be determined, what researchers learn from a necropsy—including basic measurements, age, sex and diet—will contribute to greater understanding of these species that are difficult to study in the wild.

Fast Facts:

  • Spring is migration season for whales along the California coast and therefore is also peak whale stranding season.
  • Ultimately, the most common cause of stranding remains “undetermined.” Typically, a carcass is too decomposed to determine a cause of death. Other causes of death may include trauma due to ship strike or inflicted by other species, entanglement and disease.
  • When it comes to human impacts, ship strikes are a leading cause of whale mortality, along with entanglement in fishing gear. Large whales are vulnerable to collisions with all vessel types, sizes and classes throughout the world's ocean. In California, ship strikes of gray whales are the most commonly reported, followed by fin, blue, humpback and sperm whales.
  • One whale carcass can provide samples for more than a dozen scientific studies, including genetics research, toxicology, diet studies, satellite tag placement methodology and more.
  • The Center responded to a record 28 whales in 2000, including 25 gray whales during an Unusual Mortality Event for the species.


  • Report sick and injured marine mammals to The Marine Mammal Center by calling our 24-hour hotline at 415-289-SEAL (7325).
  • Maintain a safe distance of at least 50 feet and keep dogs away.
  • The Marine Mammal Center is a nonprofit facility and depends on donations from members of the public to respond to and care for animals, including stranded cetaceans.
  • Visit to help the Center perform its life-saving work and sign up for our monthly e-newsletter.
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