Gray whale populations have plummeted to the lowest number in more than 50 years as climate change upends Arctic Ocean food webs.
New population estimates of the Eastern North Pacific gray whales are the lowest since the early 1970s, according the National Oceanic and Atmospheric Administration’s Southwest Fisheries Science Center, which on Wednesday released this year’s population estimate of just 12,900 gray whales. The calf count also cratered to just 85, the lowest since recordkeeping began in 1994.
Most gray whales eat prey at the edge of the Arctic sea ice for the energy they need to complete their epic 10,000-mile-long migration each year between their summer feeding grounds and calving lagoons in Mexico. They have endured boom-and-bust population cycles documented in the past by scientists.
But the environment these whales depend on may be changing at a pace and in ways they can’t adjust to this time. Unprecedented conditions in the Arctic due to climate change could be presenting the whales with survival challenges they have never faced before, according to NOAA.
The sea ice is the platter for their feast: Algae grows on its underside as Arctic summers bring brilliant sunshine around the clock. The algae blooms and dies, falling to the bottom, where it fertilizes fine sediments perfect for growing amphipods. Those are tiny, fat-rich crustaceans that whales filter through their baleen, plates in their mouth that strain the food out of mud they suck into their mouths.
Melting sea ice changes all that. With less sea ice, there is less surface on which the algae can grow. Retreating sea ice also means more open water, which is more energetic. Currents are washing away the fine sediments in which the crustaceans live.
These changes add up to a wholesale regime shift in this food web — and the number of whales this area can feed.
The continuing population decline from a high of 27,000 whales in 2016 is unusual because the whales have bounced back quickly from previous declines. The low calf count indicates though that reproduction has remained too low for the population to rebound this time.
Researchers in Mexico reported many dead gray whales early this year in and around calving lagoons. The Eastern North Pacific gray whale population spends a portion of the winter in the shallow, protected lagoons of northern Baja, Mexico, where mothers nurse and care for their new calves.
This past winter researchers saw few gray whale calves — perhaps because the females can’t get enough food to reproduce. Gray whales were seen eating in unusual places and eating substances they don’t usually eat — even trying to harvest food from barren sand, they were so hungry.
In all, 47 gray whales have stranded dead on the U.S. West Coast so far this year, up from 31 last year and 44 in 2023, the last year of the previous die-off. While some of the stranded whales appeared skinny or emaciated, others did not. The amount of fat that gray whales carry is a reliable indicator of their health and seems to be closely linked to their survival. Fat is happy.
But the amount of blubber a whale can pack on depends on the feeding season in the Arctic.
The findings show the value of long-term data collection to spot trends. It was just a decade ago that the gray whales were being hailed as a conservation success story, recovering from industrial whaling to a population so robust the whales were taken off the Endangered Species Act list in 1994.
But now another story altogether seems to be unfolding for these whales, recovered from industrial whaling but now stalked by climate change.
Jason Colby is a professor of history at the University of Victoria and writing a book about gray whales, a subject he is drawn to in part because of the whales’ remarkable recovery.
That success is a result of political, diplomatic and scientific effort, and international, transnational cooperation and activism on behalf of a marine mammal celebrated in three countries, Colby noted. “There’s tourism, whale sculptures, whale watching points, activist organizations, murals all along the West Coast. They have profoundly impacted human culture in lots of ways.”
And yet despite the whales’ charisma and all the effort — ending whaling; setting regulations on how close boats may approach; working to avoid ship strikes in major port areas; and reducing damage from underwater noise — “it may turn out to be a failure,” Colby said. “We may lose this amazing recovery because of the kind of bigger anthropogenic changes that we have made.
“We are in danger of losing one of the most inspiring environmental success stories I know.”
