Gray whales are dying along the Pacific coast

Editor’s Note: This story is part of the Pulitzer Center's nationwide .

Since 2019, an international group of scientists, field biologists and volunteers have been investigating a mysterious phenomenon known as an Unusual Mortality Event, or UME, that’s been killing off one the world’s heartiest survivors: the northern Pacific gray whale. In that time, the number of stranded gray whales has reached 500 — a fraction of the many thousands that likely died and sank to the ocean floor.

While its underlying cause remains elusive, many researchers point to the conditions in and around a rapidly changing Arctic Ocean. The retreating ice sheet, warming waters and a shifting ecosystem may be decimating gray whales. Understanding these threats to the whales could reveal an even broader ecological impact — and another piece of Earth's biome rewritten by climate change.

What little we do know about gray whales we owe to their coastal migration. For much of the 10,000 miles they travel in the round trip from Alaska to Baja California, Mexico, you can watch their journey, so long as you’re patient and the weather is clear.

Many of the whales seen over the past three seasons of migrations were emaciated. This sort of starvation is unusual because the gray whale, like humans, is an opportunistic predator. Whales can trap huge amounts of prey through the filter-like baleen in their jaws. There is one significant catch: These migrating marine mammals feed mainly in the northern seas, filling up on fatty, lipid-rich, small crustaceans before making the trip to Baja nonstop.

And now they have been forced to start feeding along their journey.

Last March, a whale-watching company spotted a gray whale in San Francisco Bay. Swimming around Angel Island, it was seen several times during its 40-day stay. On April 27, it washed ashore, emaciated and dead. It was found in the shadow of the mid-century homes that dot the affluent Keil Cove in the town of Tiburon.

“These stranded animals are telling us a story and it’s important for us to see that story and to share it,” said Justin Viezbicke, a coordinator of the National Oceanic and Atmospheric Administration’s West Coast Marine Mammal Stranding Network. The volunteer group responds to distressed or stranded animals along the coast.

The whale found in Keil Cove was malnourished.

It’s not an uncommon story. Earlier that month, a team of scientists from the Marine Mammal Center (MMC), an ocean conservation nonprofit, performed necropsies on four dead gray whales in the bay over the course of a single a week. “It’s alarming ... because it really puts into perspective the current challenges faced by this species,” said Dr. Pádraig Duignan in a news release from the center.

Since the beginning of the ongoing UME in 2019, whales have been coming into the San Francisco Bay to feed. In 2019, 14 dead whales were found stranded on beaches along the coast. Of those, six showed signs of malnutrition. Others showed signs of ship strikes or had an unconfirmed cause of death.

“We’re seeing more whales come into the bay. We’re seeing them stay for longer periods and they’re feeding,” said Kathi George, director of field operations and response at the MMC. “We’re fortunate to see this, but it’s also putting these whales that are in poor body condition into harm’s way.”

In 2019, the deaths of five of the whales stranded in the bay were caused by ship strikes.

Studying dead whales only reveals part of the problem — observing the whales while they're alive is key. Down the coast from the Golden Gate Bridge outside Los Angeles, a group of volunteers has been tracking whales from shore for decades.

At Point Vicente, a peninsula near Long Beach, Alisa Schulman-Janiger talks through how to sight a starved whale from a hundred feet offshore. She’s perched on the rocky coastline at the Point Interpretive Center.

With one hand, Schulman-Janiger outlines the shape of an imaginary whale: “Good body condition has a hump of fat behind the blow holes. It’s, you know, more robust,” she said. “Emaciated: big dip — because you’re looking at the skull — big dip behind the blow holes, there’s no fat storage here.”

Here, 130 feet up the cliffside, anyone with a nice set of lenses and a clear view during January can watch passing gray whales as they head south to Mexico. That's what Schulman-Janiger and her volunteers have done since 1984, as a part of the Gray Whale Census under the American Cetacean Society in Los Angeles.

“Calf counts dropped dramatically [in 2018 – 2019],” Schulman-Janiger said. Along their southern migration, gray whales mate and are pregnant or raise their young in the protective San Ignacio Lagoon in Mexico. On their northbound migration back to the Arctic, one typically sees more calf-cow pairs, but from the coast, Schulman-Janiger said, they reported 37 calves, down from 104 the previous season.

At the gray whales’ winter home in Baja California, a team of researchers are using drone photography to get up close and estimate the body weight and health of the whales. Steven L. Swartz is a senior scientist and co-director of the Laguna San Ignacio Ecosystem Science Program and has been looking at gray whales in Baja California since 1977.

His program identifies individual whales and tracks how many times they come to the lagoon and how long they stay. It also helps other groups identify these whales, should they wind up dead along the coast. Before the UME, Swartz and his team began to notice a change in the whales. “Beginning in 2017, we started to notice in our photographic identification data a slow increase at first of the number of emaciated or skinny whales in our collection,” said Swartz. In 2018, their team noticed both a 25% jump in skinny whales and a giant reduction in cow-calf pairs.

The trend continued into 2019, coinciding with the UME declaration. Meanwhile the group started seeing dead, adult whales stranded in the lagoon during the wintertime. “It was our conclusion at the time that if these whales are supposedly coming to winter breeding grounds after a summer of feeding in the higher latitudes of the Arctic, they should be fat, because they’ve been eating all summer long,” Swartz said. Instead, they observed more skinny whales turning around trying to migrate back.

Cow-calf counts provide an insight into the nutritional reserves these whales are carrying on their journey. “In large mammals,” said Swartz, “if you don’t have the energy or health to bring offspring to term and take care of it, you’ll abort it and preserve yourself at least so you’ll continue to live … Something like that is probably what contributed to the decline in the number of calves we’ve seen. We’ve lost our breeding stock, basically,” he said.

“Because they don’t feed in the winter range (of San Ignacio Lagoon) they’re just not going to make it,” Swartz remembers thinking, “and sure enough, the stranding rates spiked all along the whales’ migratory route from Mexico all the way to Alaska.”

That’s when NOAA triggered the UME for the gray whales.

When the climate history of the Arctic is written, 2017 will be remembered as a turning point. In January that year, the sea ice edge only made it past the Bering Strait. The ice was about 770,000 square miles (1,994,290 square kilometers) less than average. That’s roughly a fifth of the landmass of Canada.

Ecologists are now wondering if a threshold has been passed for the Arctic, changing the prey — and the predators that depend on them — forever.

A recent study by the San Ignacio Laguna group, which documented poor body conditions in gray whales, examined food scarcity as a potential cause for the rise in skinny whales: “[It] could also be due to a decline in prey on their feeding grounds. Benthic amphipods are of great importance to gray whales … comprising 90% of their food intake.” The study cites the correlation between sea ice cover and the reproductive health of gray whales.

Benthic amphipods are a type of tiny crustacean — think sea bug — living in usually dense communities along the sea floor out of reach from most predators.

“Have you seen photos of mud plumes from gray whales?” Janet Clarke, research scientist at the Cooperative Institute for Climate, Ocean, and Ecosystem Studies at the University of Washington, asks on a Zoom call.

“As the animal is surfacing, it’s basically got all this gunk stuff in its mouth … well then it uses its tongue to push the sediment out through the baleen. The food that it’s eating will get caught in the baleen, and the sediment gets pushed out … and so it forms this mud plume at the surface,” Clarke tells me.

The gray whale’s left with a mouthful of food that they’re uniquely suited to comb up. But the little crustaceans aren’t just convenient, they’re a highly lipid or fat-rich food source necessary to put on the miles — and pounds — later in the winter.

Where sea bugs are, gray whales gather. After an eight-hour day on Aero Commander planes, when Janet’s got a demoralized team of surveyors, she’s been known to fly to the Southern Chukchi Sea in an area called Hope Canyon. Because of the currents, it can be rich in these benthic amphipods.

“You can almost be assured of gray whales and other species actually, but it’s very much a gray whale hotspot in that area,” said Clarke.

Lately, though, grays in northeastern Chukchi have been shifting. From 2009 to 2015, Clarke said, the whales moved farther from shore. “Since about 2015 or 2016, we still see some out there, but nothing like we used to … a really noticeable shift.” Up in the air, these surveys can’t sample the ocean bottom to see what’s changing, they can only see the plumes.

Jackie Grebmeier, a professor at the University of Maryland Center for Environmental Science, however, does sample the sea bottom. She describes her research as coming from a “prey-based” mindset, meaning Grebmeier focuses on ecology through the lens of prey life and availability.

“I think the quality of food that (gray whales) are getting is less than what they did in the past,” Grebmeier said.

What her research found was that it’s not like there’s no more food for predators, just less of any single source. “The gray whale’s plate is smaller. Instead of being a dinner plate of food, now it’s like a salad plate of food,” said Grebmeier.

Key reasons for the reduction are changing currents and warming waters. The fattier sea bugs that gray whales ate en masse before are susceptible to warm waters for a few reasons. For starters: “there’s a temperature limit on a lot of these benthic animals,” said Grebmeier. “They can tolerate a lot of cold, but their thermal range … they don’t really like warm water.”

Change in temperature also changes the speed of currents. Slower waters where these sea bugs live mean more fine sediment reaches them on the floor. Like gusting winds to autumn leaves, faster currents take these fine particles farther from the sea bug's habitat. Without the “wind,” sediment settles onto the amphipod communities. Greater amounts of fine sediment impacts their ability to build content little lives in the mud.

Along with prey samples, Grebmeier also takes sediment analysis. “There’s a mixture of silt, clay, and sand they need to have … to build these tubes (to live in). And if they can’t build them, they’re not able to protect themselves,” said Grebmeier. With less material to build their homes, researchers are seeing a contraction in the population of these amphipods that used to make up the bulk of the gray whales’ diets.

On top of the sea waters, warmer temperatures spell different conditions for the sea ice and the ecology that depends on it. In a 2018 paper, Grebmeier and her colleagues analyzed whether these changes were part of a point beyond which the Arctic might not recover. Taken together — warmer seafloors and less seasonal sea ice — the ecology of the area may be transforming from a more bottom-rich (benthic) system into something found in warmer coastal latitudes: a pelagic one.

With solid ice cover, springtime brings algae blooms that feed the benthic organisms on the seafloor. If there’s no ice coverage, however, the Arctic becomes a more productive system. Sue Moore, a cetology research scientist at the University of Washington, adviser to NOAA’s UME working group and frequent collaborator with Grebmeier, said that the biomass loss may offset a little by more productivity throughout the water column.

Warmer temperatures might be pushing ecological changes for the Arctic. Throughout the Bering and Chukchi Seas where more algae, phytoplankton, and krill are emerging, gray whales are adapting to the change in food sources.

“They’ve shifted from eating benthic animals to eating animals that swarm in the water column,” said Moore. “What is the nutritional cost, if any, of basically switching your diet from primarily amphipods to primarily krill?” asked Moore. “I don’t know the answer to that yet, but it’s knowable.”

Meanwhile, a warming Arctic sees salmon running up previously too cold, or frozen rivers. A paper from Nature Climate Change, suggests that the ecosystem is transforming: “The ecosystem-wide changes seen in 2017–2019 have the potential to fundamentally reconfigure the Pacific Arctic marine food web.”

Before the 2019 UME, the eastern North Pacific gray whale's population had grown to over 25,000, making it the poster child for marine mammal recovery. Commercial whaling had nearly wiped out the Pacific grays until the practice was banned in the US in 1971 and then internationally in 1986 under the International Whaling Commission. In 1994, the whales were no longer endangered.

Part of their success story is that they're a resilient species. The Atlantic variety of gray whale was deemed extinct in the 1700s. But in 2021, a lone male gray whale was found hungry and swimming in the Mediterranean Sea. Surviving as a species on this planet for some 200,000 years can have that effect. Gray whales have learned how to make it.

“My money’s always on gray whales,” said Sue Moore. “As I’ve said — now maybe too many times — they don’t call them robustus for nothing. They are a robust species.” She’s referring to their scientific name: Eschrichtius robustus.

As humans we should stop killing them, hitting them with ships, and entangling them in fishing gear, she said. But in terms of responding to a warming climate, when compared with humans, Moore’s bet is on the whales.

There’s no better example of the whale’s hardiness than a small tribe of grays that stopped migrating altogether. Unlike their ambitious cousins, these gray whales stay in the Vancouver Island habitat. They’re known as "Sounders" because they live year-round in the northern Puget Sound area.

"The degree to which we view gray whales has really shifted in the last 20 years," notes John Calombokidis, a senior research biologist who specializes in Sounders at Cascadia Research Collective, a nonprofit dedicated to researching Washington state’s coastal ecology. "This idea that they're very regimented and had one trick that they exploited ... what's emerged is that they are the most versatile of the baleen whales."

Some 150 miles off the migration pathway, Sounders navigate the ocean through serpentine channels to find their food. The tidal shift in the region can drop some 13 feet in a matter of hours. On average the Coast Guard responds to 35 to 45 groundings a year in the region on the US side alone. But in the years of his work, Calombokidis hasn't seen a single Sounder whale stranded due to the tide.

"Maybe these changing conditions in the Arctic Circle are things they've faced before. Maybe that's why they're so adaptable," said Calombokidis.

It’s possible that we simply do not know if these whales are at the height of their population that the habitat can sustain, also known as the species' carrying capacity.

Gray whales as a population may be more resilient against the changes in climate than their terrestrial, bipedal, neighbors. In November, atmospheric rivers from a La Niña year caused rains, flooding and mudslides that cut off Vancouver’s infrastructure from the rest of British Columbia. Persistent drought across western North America and terrific rainfall are both magnified by climate change. But as a species, we are not accustomed to traveling thousands of miles to raise our offspring — or navigating tides to find food a fraction of our body weight. Gray whales are.

During a November call, Van Daele, who was in the Kodiak archipelago, said he had returned from Ugak Island after observing a gray whale feeding close along the shoreline, not unlike a Sounder would. It was the closest he had been to a live whale since 2019.

"And you know, I am probably foolish to hope, but I'm just holding on to hope that maybe this is a Sounder," he said. "And it's just getting a snack before heading further South."

Hope, because, if it was a Sounder, it might survive another winter.