Gray whales are increasingly spotted in San Francisco Bay during their migration from Mexico to Alaska, likely due to reduced food availability in the Arctic caused by climate change.
Key points
Gray whales are increasingly spotted in San Francisco Bay
They are migrating from Mexico to Alaska
Changing ocean conditions are reducing their food supply
Whales are seen near Alcatraz Island
New ship alerts could help protect them
San Francisco BayAlaskaMexicoGolden Gate Bridge
Gray whales are showing up in San Francisco Bay, a detour on their long migrations from Alaska to Mexico. They seem to be searching for food, as changing ocean conditions reduce availability of their normal prey in the Arctic.
Gray whales are showing up in San Francisco Bay, a detour on their long migrations from Mexico to Alaska. They seem to be searching for food, as changing ocean conditions reduce availability of their normal prey in the Arctic.
Darrin Allen/The Marine Mammal Center, NOAA
Darrin Allen/The Marine Mammal Center, NOAA
Gray whales used to be a rare sight in San Francisco Bay. Now, their spouts are appearing off Alcatraz Island in one of the busiest waterways in the country.
The whales are making a pitstop on their long migrations from Mexico to Alaska, detouring under the Golden Gate bridge for a snack as climate change is shrinking their normal food supply in Arctic waters.
But as gray whales try to adapt to one human-caused impact by feeding in San Francisco Bay, it's putting them squarely in the path of another hazard: ships.
Why are gray whales appearing in San Francisco Bay?
Gray whales are appearing in San Francisco Bay as they search for food due to changing ocean conditions that have reduced their normal prey in the Arctic.
What impact does climate change have on gray whales' migration?
Climate change is shrinking the availability of food in Arctic waters, prompting gray whales to detour into San Francisco Bay during their migration.
Where are gray whales commonly spotted in San Francisco Bay?
Gray whales are commonly spotted off Alcatraz Island and under the Golden Gate Bridge in San Francisco Bay.
How can ship alerts help protect gray whales in San Francisco Bay?
New ship alerts can help protect gray whales by warning vessels of their presence, reducing the risk of collisions in busy waterways.
Of 16 gray whales seen in San Francisco Bay this year, seven have died. Researchers have found evidence that several were killed by ship strikes.
With some whales now hanging out in the bay for weeks, a coalition of marine scientists and local officials are trying out a new system to prevent collisions.
Researchers installed a thermal camera on an island in the bay that can spot heat from the whales' exhalations. Potential whale sightings are screened by artificial intelligence and then confirmed by human screeners. The U.S. Coast Guard can then use that information to alert vessels and ships.
"We want the word to get out," says Gary Reed, director of Vessel Traffic Service San Francisco for the U.S. Coast Guard. "We want people to know there are whales in a particular location so they don't encounter them."
Ferries, container ships and other boats crisscross San Francisco Bay, making it one of the busiest waterways in the country. Several gray whales have already been struck and killed this year.
Lauren Sommer/NPR
Lauren Sommer/NPR
Gray whales in the North Pacific are declining. The current population is around 13,000, half of what it was a decade ago. Last year, 22 gray whales died in the larger San Francisco Bay Area, the highest number in 25 years. The same is happening in other areas along the West Coast.
"We're looking at a moment for gray whales where every whale that comes in and goes out of the bay matters for population," says Douglas McCauley, director of the Benioff Ocean Science Laboratory at the University of California Santa Barbara. "So even though this is just one piece of the problem, it's a piece that we want to solve, can solve."
Climate change ripple effects
On a beach on Angel Island, the giant vertebrae of three whales lie in a row on the sand. They're the remnants of whale necropsies – animal autopsies done by two Bay Area research institutions, the Marine Mammal Center and the California Academy of Sciences. When a dead whale is spotted, the researchers rapidly try to assess the cause of death.
Whale carcasses lie on a beach on Angel Island in San Francisco Bay, Tuesday, May 19, 2026.
Skeletons are all that remain of three gray whales that died in San Francisco Bay this year. Researchers quickly did animal autopsies to determine the cause of death.
Annika Hammerschlag/AP
Annika Hammerschlag/AP
Broken bones and bruised tissue are often a sign of ship strike.
That's visible in the middle skeleton, from a female that came into the bay this year, says Kathi George, director of Cetacean Conservation Biology at the Marine Mammal Center.
"She died from injuries due to blunt force trauma from vessel strike," George says.
In recent years, an alarming number of whales have also been washing up malnourished, both in California and in the Pacific Northwest.
Gray whales undertake one of the longest migrations of any mammal, traveling around 12,000 miles roundtrip every year. They spend the summers feeding in the cold waters of the Arctic, where prey is abundant. Then they swim to Baja California, Mexico for the winter, where they have their young.
In the Arctic, gray whales need to fuel up, building the reserves necessary for such an arduous migration. Their goal is to start the trip with a full tank. But lately, that's been harder to do.
Sea ice is shrinking in the Arctic, one the fastest warming places on the planet. That fundamental shift is altering the ecosystem, reducing the availability of the tiny, shrimp-like animals that gray whales like to feed on. Gray whales need to eat more than a ton of them per day. As a result, scientists believe that whales are running out of fuel before they can finish their migration.
"These whales are hungry," George says. "We think they're stopping at different areas along their route to find sources of food, and San Francisco Bay has become one of those hotspots."
Not far from the span of the Bay Bridge, a puff of spray, the sign of a whale breathing, appears in the distance. Shawn Henry, CEO of WhaleSpotter, pulls up an image on a laptop to show how his company's camera detects the whale's exhalation.
"That blow is a little bit warmer than the water and the air around, so it provides a very good thermal signature," Henry says.
A WhaleSpotter thermal camera has been installed on a tower in the middle of San Francisco Bay. It detects whale spouts using artificial intelligence, helping alert nearby vessels.
Lauren Sommer/NPR
Lauren Sommer/NPR
Once it's detected, the whale's position is posted on the WhaleSafe website, run by UCSB's Benioff Ocean Science Laboratory. The Coast Guard then uses the information to alert vessels over the radio about a whale's position. Before this project, Coast Guard alerts relied on visual reports of whales from vessels during the day.
"Now with this new technology, it'll show us whales at night, so we can identify them and notify traffic," says the Coast Guard's Reed.
Another camera is also being installed on a local ferry. The Bay Area's two ferry companies say their operators either slow down or go around the areas where whales have been seen. It's tougher for larger container ships, which are much less maneuverable and are constrained to specific shipping lanes in the bay.
For now, the effort is voluntary for ships. On other parts of the California coast, researchers have seen significant compliance with voluntary speed limits from shipping fleets without mandatory regulations, McCauley says.
"I'm really optimistic that this is one of those solutions where the community comes together, and the community solves it, but we'll see," he says.
Conditions for gray whales may only get more challenging in the future, McCauley says. The whales are showing an ability to adapt, but it may only go so far.
"The world is changing, they're trying their best to change themselves," he says. "The one thing they're not doing is quitting."
