A necropsy was completed Tuesday morning by scientists from The Marine Mammal Center and its partners at the California Academy of Sciences on the gray whale at Ocean Beach in San Francisco.
They found the cause of death to be blunt force trauma likely attributable to a ship strike. The animal, stranded on Ocean Beach on Monday, was the ninth gray whale to wash onto the shores in the Bay Area this year. The scientists discovered multiple fractures on the animal’s skull and upper vertebrae and significant bruising in the surrounding area consistent with injuries resulting from a collision.
The Marine Mammal Center identified the whale as a 41-foot adult female in the early stages of decomposition. The team of scientists noted its blubber layer was thinner than expected, which indicated it had been in poor health.
According to the center, an increased number of gray whales have been spotted this year. Representatives said that biologists have observed the species to be in poor condition as it migrates north, possibly because of its shifting food sources.
Center officials speculated that over-fishing and water temperature changes associated with climate change might be contributing to reduced prey availability for gray whales.
Dr. Padraig Duignan, chief research pathologist at the center, said that malnutrition might correlate with the relatively high number of beached whales this year.
Duignan said in a statement:
“As gray whale migration season enters its final stages of the season, adult female gray whales and their calves with low body reserves are the last to migrate northward to their feeding ground in the Arctic. … These mother whales are worn out and running on empty, making them even more susceptible to negative human interactions, including ship strikes and entanglements.”
Officials at the Golden Gate National Recreation Area are currently coordinating the removal of the whale’s remains from Ocean Beach, said representatives of The Marine Mammal Center.