In an unusual spate of gray whale deaths, another animal was found in San Francisco Bay, this time on Muir Beach Thursday morning.
April marks the beginning of the gray whale’s north migration. So it’s not uncommon to find dead whales on the shores of the bay, but four in nine days is an anomaly.
“It’s about that,” says Giancarlo Rulli of the Marine Mammal Center in Sausalito. “The fact that we responded to four gray whales dead … is worrying.”
The first was a 41-foot adult female gray whale that alerted beach goers at Crissy Field on March 31. This animal was dragged to Angel Island for an autopsy. The cause of death was unclear – pathologists from the Marine Mammal Center determined the whale was in good condition, no diseases were found, and in fact the whale had a full stomach from recent feeding, which ruled out starvation or malnutrition.
The second, another adult female, was found Saturday at the Fitzgerald Marine Reserve in Moss Beach. “We suspect that the cause of this animal’s death was a ship strike,” says Rulli. “Our plan is to come back to this whale at some point and take more samples.”
A third dead gray whale was found at Berkeley Marina this week after moving around the bay during changing tides. This animal was also towed to Angel Island and is currently being inspected near the remains of the first animal.
“Our team is currently divided into two parts,” says Rulli, as pathologists examine and sample both animals at Muir Beach and Angel Island.
There was also an increase in dead gray whales around the waters of San Francisco in 2019, despite half of the causes of death for these animals being classified as malnutrition, a cause that has not yet been clarified for any of the four whales this week.
“These studies are so critical that we can find out why these animals wash ashore dead and how we can live together safely in their ocean home,” says Rulli. “This is an unusual death event for gray whales. In the past two years, an increasing number of dead whales have washed ashore.”
Human interaction, usually in the form of a ship strike or entanglement, is a common cause of whale deaths, although only one of the four was pronounced dead that week as a result of that trauma.
The deaths have resulted in the Marine Mammal Center facing one of the busiest times due to COVID-19 while prioritizing human health and safety.
“Because of the pandemic, we’re using smaller teams than normal, and that’s more than 40-foot whales. These surveys take hours,” says Rulli. “It can take some time to find out what happens.”
The increased deaths aren’t the only unusual whale activity in San Francisco Bay this year. In mid-March, a hump was discovered near Tiburon, something that had never happened so early in the year before.
The center encourages all residents of the bay who discover more dead (or live) whales to report the sighting to the Marine Mammal Center immediately.
“The data and research are so critical that we can rule out or rule out the cause of human interaction,” said Rulli.
The cause of death of the last two whales is expected to be reported on Friday.
SFGATE reporter Joshua Bote contributed to this story.