As spring gray whale migration begins, scientists watchful for another die-off

Mar 10, 2020

Last year, during the spring northbound migration of gray whales along the Pacific Northwest coast, more than 200 whales -- most looking skinny or malnourished -- washed up dead on beaches between Mexico and Alaska.

As this year's long journey gets underway, marine scientists and whale lovers will be watching whether the unusual die-off continues into a second year.

Gray whales overwinter in the warm waters of Baja California. Their migration along the West Coast back to summer feeding grounds off Alaska extends from February through June. 

The first gray whales have already made it to Washington state. It took an Island Adventures Whale Watching tour barely 15 minutes to find some of them on the company's first gray whale trip of the season out of the Port of Everett on March 7. 

Whale watchers on board spontaneously cheered and applauded when they got nice looks at individually-recognizable whales named "Patch," "Little Patch" and a third adult known only as "531." The beasts are each roughly the size of a school bus.

"I'm pretty hopeful seeing Patch coming back, seeing Little Patch," said Island Adventures naturalist Tyson Reed. Reed said the whales looked bulky and did not appear malnourished as so many of last year's casualties did. "So, I'm hoping that's a good sign," he said. 

Also along for the season-opening cruise was a leading whale expert, senior biologist John Calambokidis of Cascadia Research in Olympia. He made a similarly positive assessment of the body condition of the early arriving whales. He hesitated to predict if last year's die-off will continue into 2020.

"The limited information we have gotten so far has been a little ambiguous," Calambokidis said in an interview. "It may be another month before we know for sure."

The distinctive white spot on the back of this gray whale is what gave Patch his nickname.
Credit John Calambokidis / Cascadia Research Collective

Calambokidis said the gray whales the tour boat encountered were a familiar subgroup that consistently takes a detour and extended break from the northbound migration. This group of up to 12 discovered a veritable private buffet in North Puget Sound -- hence their nickname, the "Sounders." At high tide, they swim into the muddy shallows of Possession Sound, Port Susan and the Snohomish River Delta to gorge on ghost shrimp.

Gray whales are typically bottom feeders, preferring to filter tiny crustaceans from the seafloor.

Federal agencies remain concerned that last year's die-off within the broader gray whale population may extend into this year's migration. The previous time this happened two decades ago it stretched two years.

"So it seems possible, if not likely, that we'll see elevated strandings again this spring as these whales head north and some of them, as happened last year, kind of run out of energy on that northbound trip," said Michael Milstein, a spokesman in Portland for the federal marine science agency NOAA Fisheries.

Milstein said his agency has gotten reports of 36 dead gray whales in Mexico this year and five deaths so far on the U.S. West Coast -- four in California and one on the Washington coast.

He said observers have also noticed more whales making uncharacteristic detours during the northbound migration into bays and inlets, such as Long Beach Harbor and San Francisco Bay. Milstein said these could be feeding forays akin to what the Sounders do.

When last year's numbers began spiraling up, the federal government made a disaster declaration of sorts.

"The declaration is what we call an 'Unusual Mortality Event,'" explained Milstein, and it is still in effect.

The UME is important because it freed up additional resources for scientists to study what the underlying causes of the die-off might be. Many government, academic and nonprofit institutions are lending scientists to this investigation, including Oregon State University, University of Washington, Cascadia Research and Seattle-based SR3.

Cascadia Research senior biologist John Calambokidis is studying what factors might explain an unusual die-off among gray whales that migrate along the West Coast.
Credit Tom Banse / NW News Network

Calambokidis said the research is organized into three prongs with different groups looking into possible causes. One group is looking into whether something is wrong in the Arctic food chain. Another scientific committee is studying gray whale population dynamics. Other specialists will try to rule out disease or toxins.

A leading theory is that starving whales could be a function of an increasing gray whale population intersecting with a downturn in their prey in the Arctic.

"There are such dramatic changes occurring in the Arctic ecosystem with climate change that is occurring," Calambokidis said. "We have to make sure this isn't a sentinel of some of the problems that are occurring up there."

The annual migration of eastern Pacific gray whales totals around 10,000 miles roundtrip, which makes it among the longest migrations of any mammal on earth. Commercial whaling reduced the population to near extinction by the early decades of the last century, but these whales have staged a remarkable recovery.

Eastern Pacific gray whales were taken off the endangered species list in 1994. The population is now estimated at roughly 27,000, which may be around the carrying capacity of their ocean territory.

"We also know the population did fully recover from that 1999-2000 event," Calambokidis said, referring to the previous die-off. "So we do know it can survive these types of events."

NOAA has teams at the ready to respond to a new wave of dead whales, if that happens during this year's migration. Milstein said the pre-season planning identified a goal to get on scene quickly to do necropsies and collect tissue samples while the carcasses are still fresh.

If you see a stranded or dead whale (or other marine mammal in distress), you can report it to the West Coast Marine Mammal Stranding Hotline: 1-866-767-6114.

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