These sea creatures are 90,000-pound giants that grow up to 49 feet long. Females of the species are slightly larger.
While not the biggest, gray whales have the longest migration of any mammal species on land or sea: upwards of 14,000 miles.
Scientists don’t know the average lifespan of these creatures, but one female was found to be as old as 80.
Hunted to the brink of extinction, conservation efforts since the 1930s brought the local species — the Western Pacific gray whales — back to their previous abundance, at least until recently.
A die-off of the species began in 2019, and it’s still underway. So far there’s been a 25% decline in their numbers.
"These are extreme population swings that we did not expect to see in a large, long-lived species like gray whales," said Joshua Stewart, an assistant professor with Oregon State University’s Marine Mammal Institute.
Stewart published a study in September in the journal "Science" that tracked two other previous die-offs as well, though neither of the previous ones were as "significant and dramatic."
All appeared to be related to a warming climate — less ice in the Arctic led to less food.
"We are in uncharted territory now. The two previous events, despite being significant and dramatic, only lasted a couple of years," Stewart said. "One reason it may be dragging on is the climate change component, which is contributing to a long-term trend of lower-quality prey."
Stewart is optimistic that the species will survive, given that they’ve adapted to changing conditions for millennia.
"I wouldn’t say there is a risk of losing gray whales due to climate change," he said. “But we need to think critically about what these changes might mean in the future. An Arctic Ocean that has warmed significantly may not be able to support 25,000 gray whales like it has in the recent past."