One was reportedly hit by a ship and the other died due to severe entanglement.
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The Marine Mammal Center says both whales were discovered on Friday, May 18. First, a fin whale surfaced near Jack London Square and was later towed to Angel Island State Park.
A team of nine scientists from the Marine Mammal Center, California Academy of Sciences and UC Davis performed a full necropsy Monday afternoon at Angel Island State Park.
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Scientists discovered fractures and dislocated vertebrae surrounded by massive hemorrhaging on both sides of the 45-foot juvenile female whale. The cause of death was determined to be vessel collision.
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On Friday afternoon, the Center received reports of a second whale carcass that washed ashore on Tennessee Valley Beach in Marin County. Scientists from the Center and California Academy of Sciences performed a full necropsy on the 36-foot adult female gray whale on Saturday morning, May 19.
They found linear lesions that looped around the back of the neck and along both front flippers, which are injuries consistent with an entanglement, said officials.
The team also found two lacerations on the animal's right side with multiple fractures to the skull, consistent with a ship propeller. The necropsy team concluded that these ship-related injuries were likely sustained after the animal's death.
"The deaths of these two whales highlights the direct negative impact humans can have on marine wildlife," says Dr. Shawn Johnson, Director of Veterinary Science at the Marine Mammal Center.
"The whale autopsy work the Center and its partners perform is critical to better understand the challenges these animals face and inform decision-makers so we can all safely share the ocean with marine wildlife," says Johnson.