“That’s the question that we’re all asking,” said Moe Flannery, an expert in marine mammal necropsies at the California Academy of Sciences.
The increase in local whale traffic is surprising, as the numbers of northern Pacific gray whales are at historic lows. Between 2019 and 2023, the number of gray whales in the region fell by about 40%, an episode known as an “unusual mortality event,” and it is now at the lowest point since the 1970s.
Experts attribute this to a climate-change-propelled decrease in “quality prey” — namely, shrimp-like crustaceans — in the whales’ arctic hunting grounds, Flannery said. That lack of edible invertebrates could now be driving more whales into the bay.
Michael Pierson, a field operations specialist who leads whale tours to the Farallon Islands for the Oceanic Society, explained that the whales feed only in summer. Those that didn’t get enough to eat last summer may be “running out of gas” on their return to the Arctic from Mexico, where they go to breed and give birth, and venturing into the bay.
“We might be seeing gray whales stopping off in the San Francisco Bay to forage on their way up to Alaska, which would be a new behavior,” Flannery said, adding that the theory is unconfirmed.
But whales venturing in for a meal must contend with shipping vessels, ferries, and other large ships traversing the bay. Ship strikes accounted for nearly half of recorded deaths of whales so far this year; for nearly all others, the cause of death was “undetermined.”
“When these whales come in here to feed, it’s like they’re trying to have dinner in the middle of a freeway,” Pierson said.
In an attempt to create safer waters for our mammalian brethren, experts will convene this week in Sausalito to “[look] into potential gaps in research, strengthen scientific collaboration work, and bolster ongoing whale safety efforts,” according to a Marine Mammal Center spokesperson.
While no representatives of the San Francisco Bay Ferry or shipping industry will be present at the meetings, experts may brainstorm recommendations for altering ship routes. Flannery said there has been progress this year: more communication between vessels and the diversion of ferry traffic during certain weekends to avoid whale activity. But she added that it can come down to the discretion of the captain, and not everyone slows or changes course to protect whales.
“Nobody wants to hit a whale,” Flannery said, “but now that things are changing, we all have to make sure we also adapt and change our behaviors.”