Federal officials have declared the end of the die-off of eastern Pacific Gray Whales that migrate along the west coast. The so-called “unusual mortality event” killed off about a third of the population from December 2018 to November 2023.
A total of 690 emaciated whales were counted that washed up on beaches, representing perhaps a tenth of the total number that died.
According to the National Oceanic and Atmospheric Administration (NOAA), the most recent estimate of the total population is just over 19,000.
The whales are now expected to rebound, according to investigations led by NOAA. The agency documented the pace of strandings while also counting births of gray whale calves in the lagoons of Baja, Mexico, where they are born before continuing on their annual migration to the Alaskan Arctic, where they feed.
Investigators determined that the cause was associated with localized ecosystem changes in the whales’ Subarctic and Arctic feeding areas, which led to malnutrition and decreased birth rates.
A decline in the number of strandings and deaths triggered the agency to declare the end of the die-off. The observations of these whales’ resilience in the past give many researchers hope for their future.
“This looks like it was the third major mortality event that occurred with gray whales,” said John Calambokidis with Cascadia Research Collective in Olympia.
He has investigated gray whale strandings on the west coast for over 30 years, primarily in the Pacific Northwest. He said a pattern has emerged in which the species hits a peak population, then dies down and rebounds again.
They rebounded from the massive commercial whale hunting era that pushed them to the brink of extinction and led to their listing as an endangered species in 1970 till they were de-listed in 1994.
The last natural die-off ended in the year 2000. So, scientists are generally optimistic that this latest die-off is part of a natural cycle.
“But it is very worrisome that there are very dramatic changes occurring in the arctic environment,” Calambokidis said.
This time, it’s not clear how much of the die-off was due to climate-driven changes in food availability and how much was due to population pressure, as in the past.
“So I can say I can be hopeful that there'll be a similar rebound as there were to the previous two’” he said. “But I can't say we have hard data to support why that will necessarily happen.”
He’s hopeful because the species is proving to be adaptable, developing new feeding strategies up and down the west coast. The whales appear to be far more adept at trying new things than previously known.
Calambokidis has documented a local group of gray whales known as “the Sounders” that take a detour into Puget Sound each spring to fill up on ghost shrimp, before heading to their main feeding ground in the Arctic.
He’s currently studying how newcomers to the small group of Sounders fare, including one whale that stayed in Puget Sound for a full year rather than continuing on the annual marathon-like migration between the Arctic and Mexico.
“There are other examples of unique and different feeding behaviors, whether it's animals stopping off and feeding on herring spawn or exploring new feeding areas and new habitats off Kodiak Island,” Calabokidis said. “So we do have a number of other examples that in total, could represent a substantial number of gray whales.”
He said the way they’re seeking out alternate options makes him optimistic that some portion of the species will adapt and survive. But he added it’s not clear how much of the population will succeed in making these changes. He said the tremendous speed of climate change could challenge their adaptability.
Produced with assistance from the Public Media Journalists Association Editor Corps funded by the Corporation for Public Broadcasting, a private corporation funded by the American people.
