Many gray whales returning south from feeding grounds off Alaska have been passing observation posts in California and Mexico underweight, according to some scientists.
In some cases, the large bottom-feeding cetaceans were skinny enough that bones were showing, raising concerns that food stressed whales could be poised for another die off.
The eastern North Pacific stock of gray whales is one of the world’s great recovery success stories, rebounding from near extinction to get removed from the federal endangered species list. But now the fast-warming ocean off Alaska might be making food much harder to find. Or is something else at work?
So far, scientists only know that trained observers say many whales appear far too skinny for the season.
An Associated Press story this week outlined the most recent concerns by biologists, and has been picked up around the world. But a more comprehensive story appeared about two months ago in the LA Times, when the observers first began raising the alarm.
Published July 6, A Giant of the Sea Finds Slimmer Pickings reported one biologist noticing a scapula sticking out of a particularly scrawny female off San Simeon. It adds:
Scientists from Mexico to the Pacific Northwest are reporting an unusually high number of scrawny whales this year for the first time since malnourishment and disease claimed a third of the gray whale population in 1999 and 2000.
So far this year, scientists haven’t seen a decline in numbers, and they are not sure what’s causing the whales to be so thin. But they suspect it may be the same thing that triggered the die-off eight years ago: rapid warming of Arctic waters where the whales feed.
Reaching 46 feet in length and weighing up to 33 tons, the animals are the only bottom-feeding whales, filtering invertebrates from muck through their yellow baleen. Once hunted to the brink of extinction, gray whales have rebounded in recent decades and may number more than 20,000 in the North Pacific.
Here’s what the AP’s Dan Joling reported this week:
Researchers off Mexico’s Pacific coast have observed what might be a case of global warming’s effects in the far north: gray whales returning to calving grounds malnourished.
Where layers of fat should have covered whales’ spines last winter, researchers saw vertebrae sticking out. They spotted other signs of malnutrition — depressions around the blowholes and head, and protruding shoulder blades — that may indicate declining health.
At least 10 percent of gray whales returning to Laguna San Ignacio, one of four main calving and breeding lagoons off Baja California, Mexico, showed signs of being underfed, said Steve Swartz, a National Marine Fisheries Service whale expert based in Silver Spring, Md.
Researchers are trying to find out if it’s a warning sign that climate change in the North Pacific is affecting the tiny crustaceans the whales suck up from the ocean floor, and if switching to alternative prey will affect their well-being.
“They may have to work harder for less,” Swartz said. “There are all kinds of things we’re thinking about, trying to piece the puzzle together.”
Skinny whales aren’t the only indication that gray whales may be dealing with shifting conditions. In July, scientists reported that they had picked up gray whale calls in the Arctic Ocean on submerged recording devices — during the winter beneath solid ice.
Their annual journey from Mexico to the Bering Sea and back south draws attention from all over the world. The grays serve as the regional harbinger of the ocean bloom, leading a bird and mammal convergence that concentrates killer whales, seals, sea lions, sea birds on the Bering and Chukchi seas.
[...] Are gray whales getting skinny? [...]