Starvation has decimated gray whales off the Pacific Coast. Can the giants ever recover?

Despite the hundreds of whales that washed ashore, researchers could only properly examine 61.

That’s because the majority of reported carcasses were either discovered weeks or months after the animal had died — and were far too decomposed for proper analysis — or they were located on remote islands, inaccessible coves, or the prows of ships at sea.

Of the 61 whales they examined, researchers determined the cause of death in just over half. Sixteen were severely emaciated and likely died of starvation; 11 died of blunt force trauma — although two of those whales were also extremely underweight; at least three bore fatal wounds from killer whales and two were tangled in fishing gear.

Overall, 18 whales were considered emaciated, 27 deemed “thin,” nine average and two fat. In the five others, nutritional state could not be determined.

One thing that was clear: The die-off wasn’t due to disease.

Large animal die-offs are often due to biotoxins, viruses or bacterial infections. The avian flu currently circulating around the globe is one example. The domoic acid outbreak during the summer of 2023, which killed hundreds of sea lions and dolphins, is another.

“We didn’t find any evidence of anything that looks like an infectious disease,” said Duignan. “There were no telltale signs of infection of any kind. And we did do a lot of testing for viruses, bacteria, toxins, and there was nothing significant.”

Now, the question is whether the gray whale population will recover, continue to decline, or has hit a level that is sustainable, considering the massive changes occurring in their summer feeding grounds.

Raverty noted that during this latest investigation, reports of unusual feeding behavior by the whales was observed relatively frequently. While the biological mantra had always been that gray whales feed only on bottom-dwelling organisms in the northern seas during the summer months — and fast for the rest of the year — reports came in of gray whales filter feeding and skimming krill off the surface, in places such as San Francisco Bay.

The ability of gray whales to adapt has long been known — but the frequency with which these behaviors were occurring suggested to some an immediate adaptive reaction to lack of food, or possibly behaviors no one had ever really paid heed.

That’s partly what is so exciting about this research, said Raverty. It enabled scientists to build a baseline upon which they can now make comparisons.

“If we look at another five or 15 years, if we get another recurrence,” he said, they’ll have this data with which to compare.

As for the future and population recovery?

“The way I think about this is ... these whales aren’t going away. They’re not going to go extinct,” Stewart said. “But if the environment becomes much more marginal, we might just not see as many whales as we have had in the past when we had really robust, productive Arctic [seafloor] habitats.”