A scientific journal published in 2022 reported a decrease in the ocean's crustaceans in the northern Bering and Chukchi seas, leading to the gray whales' malnutrition. A year later, another scientific study pointed to the food scarcity as one of the potential effects of climate change, saying the lack of sea ice is reducing the availability of the Arctic prey.

"This may help explain why many of the gray whales that stranded along the West Coast beginning in 2019 were skinny and emaciated — they had not eaten enough to support their long migration of about 10,000 miles round-trip, which is one of the longest known migrations of any animal," Milstein said.

Killer whale predation, entanglement in fishing nets, biotoxins and collisions with vessels also contributed to the gray whale deaths. But these factors were not as significant as malnutrition, researchers said.

This kind of dramatic die-off also occurred between 1999 and 2000 and two other times in the early 1990s, said John Calambokidis, researching biologist and part of the group that investigated the recent unusual event. What he and other scientists found interesting, Calambokidis said, was the dramatic fluctuation in the gray whale population before the mortality event.

He said that when the whale population reaches the limits of the environment's carrying capacity, there would be a decrease in the reproductive rate and a slight increase in the mortality rate that would bring the population to a plateau. Gray whales seem to have gone through these more dramatic vacillations, enduring three different periods of major mortalities and bouncing back before the most recent five-year event.

As gray whales recover to levels "that are near the limits of the food supply, then suddenly they become much more vulnerable to any fluctuations in that food supply," Calambokidis said.

Milstein added that gray whales were hunted to near extinction during the whaling era, but with the protections of the Marine Mammal Protection Act and the Endangered Species Act, the animals have recovered to the point where they were removed from endangered species protection in 1994.

More recently, the agency noted that the startling number of strandings that spiked at the start of the unusual mortality event has since declined to annual numbers similar to those recorded before the event began.

A gray whale washed up ashore in Orange County on Feb. 8 and another in Malibu this month, ABC7 reported.

©2024 Los Angeles Times. Visit at latimes.com. Distributed by Tribune Content Agency, LLC.