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As gray whales make their annual migration to their Arctic feeding grounds, four have washed up dead on Alaska's shores. This comes after at least 60 gray whales were found dead earlier this year along the Pacific coast from California to Washington, the most in nearly two decades. The whales aren't getting enough to eat. But scientists aren't sure why, and they're hoping the dead animals in Alaska can supply some answers. Nat Herz is with Alaska's Energy Desk.

NAT HERZ, BYLINE: Trust me on this one; i - you're going to slice open a dead whale, you want a sharp knife. Kathy Burek and her crew are trying to get inside a newly beached gray whale just off a highway outside Anchorage. She brought more than a dozen knives, but she hasn't had time to sharpen them since carving up another dead gray whale a couple of days before. So Burek pulls a couple of volunteers out of a crowd of bystanders and puts them to work.

KATHY BUREK: Oh, careful.

UNIDENTIFIED PERSON: It scares me a bit holding it like that.

BUREK: Yeah, maybe hold it on its side there. There you go. I like that much better.

HERZ: It's a busy time for Burek, who's a veterinary pathologist. That means she studies animal disease. She's hired by the federal government to collect samples from whales when they die. This one bobbed around for nearly two weeks before it washed up on shore, and Burek says it's too decomposed to yield many useful samples.

BUREK: Because once we get inside the abdomen, like, the kidneys and the liver are just going to be kind of liquefied.

HERZ: Before they get started, Burek and her crew get into chest waders, then pull on plastic gloves all the way up to their shoulders and put on purple rubber gloves over those. Then they slice through a 6-inch layer of blubber.

(SOUNDBITE OF KNIFE SLICING)

HERZ: Just from looking at it, Burek can tell it's underfed. That's also been the case with many of the other gray whales found dead along the West Coast this year. Because Alaska is at the tail end of the whales' 5,000-mile migration from Mexico at this time of year, more deaths are expected. John Calambokidis is a research biologist in Washington.

JOHN CALAMBOKIDIS: The level we've seen on the West Coast means Alaska should brace itself for probably some significantly elevated numbers of gray whale strandings.

HERZ: Right now, the gray whale population is healthy. It's recovered to 27,000 since whalers hunted them nearly to extinction. Calambokidis says it's starting to look like that's as many as the whales' habitat can support. He says when the whales were feeding in the Arctic last summer, it looks like it may have been a bad year for their prey. Researchers are looking at whether the whale deaths are a natural result of more animals competing for food in a limited area or if it could relate to climate change - things like warming ocean temperatures and less sea ice in the whale's feeding grounds.

Michael Milstein, a spokesman for the National Oceanic and Atmospheric Administration, says his agency is paying closer attention to annual summer surveys of the gray whales' feeding patterns.

MICHAEL MILSTEIN: The scientists that do those surveys are going back through their records and trying to understand if there was something unusual about when and where the whales were feeding.

HERZ: Scientists can also get useful data from dead whales if they wash up on shore, like this one near Anchorage. Burek, the veterinary pathologist, has finally gotten under the layer of blubber and into the whale's abdomen, which is swollen with gas and liquid.

BUREK: Oh, boy. I just - can I take a little break here?

HERZ: While the inside of the gray whale doesn't smell fresh, it turns out its organs are surprisingly intact.

BUREK: Oh, guess what that is? That's the kidney right there. Look at that kidney.

HERZ: Burek cuts off tiny chunks of tissue and puts them into bags and vials for analysis later, potential clues for researchers trying to solve the mystery of what's happening with the gray whales. In Anchorage, I'm Nat Herz.