Sixty gray whales have been found dead along their spring migration route, including two in Alaska. 

On Tuesday, a team of marine biologists performed a necropsy on a 12.5-meter male gray whale beached along the Turnagain Arm near the Placer and Twentymile rivers. The whale was first reported dead May 9, according to the National Oceanic and Atmospheric Administration.

The dead whale was easily spotted from the Seward Highway, where dozens of people stopped to watch the scientists work.

Veterinary pathologist Dr. Kathy Burek says the number of gray whale deaths is unusual. Her team is looking for clues into what may be causing the spike.

The whale found in Turnagain Arm is one of two gray whales recovered in Alaska this week. On Sunday, Burek took samples from a female gray whale found dead near Cordova.

Many of the whales studied so far were skinny and malnourished, according to NOAA. Burek says that wasn't the case with the first whale but that the male appears to follow the trend.

Tissue samples will help determine if the whale was exposed to harmful algal blooms, had an illness and other possible reasons the whale died. Researchers say the samples will take several months to process. 

“The best theory right now is that their feeding grounds were not good last summer," Burek said. "So then they travel down to the places where they have the calves, and they don't eat during that time or during the migration, and they just don't have enough reserves to make their way back up. So they are dying in California and Oregon, and Washington and now up here."

Gray whales make one of the longest annual migrations of any mammal, traveling up to 10,000 miles round-trip, between winter nursing lagoons in Mexico to summer feeding grounds in the Arctic.   

Scientists believe the number of grays whales that have died this season is likely much higher than the number found washed up on shore.

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