April is the start of gray whales' northern migration, so finding dead whales on the shores of the bay is not unusual, but after four were found in the span of nine days just a few weeks ago, experts began to worry.
"It's concerning," Giancarlo Rulli of the Marine Mammal Center in Sausalito had said. "The fact that we've responded to four dead gray whales ... is concerning."
A video of the fifth dead whale was post to Twitter:
The first dead whale to be found was a 41-foot adult female gray whale at Crissy Field on March 31. That animal was towed to Angel Island for a necropsy. The cause of death was unclear — pathologists with the Marine Mammal Center found that the whale's condition was good, no illnesses were found, and in fact, the whale had a full stomach from a recent feeding, ruling out starvation or malnutrition.
The second, another adult female, was found April 3 at Fitzgerald Marine Reserve at Moss Beach. "That animal's cause of death, we suspect, was ship strike," Rulli said. "Our plan is to eventually head back out to that whale and take more samples."
A third dead gray whale was found in the Berkeley Marina on April 7, after moving around the bay on the changing tide. That animal was also towed to Angel Island and was being inspected near the remains of the first.
The fourth dead gray whale was discovered the next morning, April 8, at Muir Beach.
In 2019, at least 13 dead whales washed ashore in the Bay Area and scientists said they feared it was because the animals were starving and couldn't complete their annual migration from Mexico to Alaska. Biologists have observed gray whales in poor body condition during their annual migration since 2019, when an "unusual mortality event" was declared by the National Oceanic and Atmospheric Administration.
Malnutrition, entanglement in fishing gear, and trauma from ship strikes have been the most common causes of death found by the center's research team in recent years.
A necropsy of the whale found at Muir Beach revealed significant bruising and hemorrhaging to muscle around the whale's jaw and neck vertebrae consistent with blunt force trauma due to ship strike. But experts noted the whale was in good body condition based on the blubber layer and internal fat levels, the center said.
The Associated Press contributed to this report.
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