Biologists from the U.S. government have launched a special investigation into the deaths of over 75 gray whales that washed ashore the U.S. West Coast and Canada over the past few months, appearing abnormally thin and weak.
The National Oceanic and Atmospheric Administration (NOAA) called the mass whale deaths, which occurred from Alaska to California, an "unusual mortality event," which may force officials to donate more resources so they can determine the cause.
Officials at NOAA's National Marine Fisheries Service say 37 gray whale corpses have washed ashore on the California coastline, three in Oregon, 25 in Washington, five in Alaska, and five in British Columbia, according to Reuters.
John Calambokidis, a biology and gray whale expert with the Cascadia Research Collective, says he's now seeing gray whales in unusual places. Whales have been spotted in San Francisco Bay, where he says they face a greater risk of getting hit by boats.
“We are seeing lots of live gray whales in unusual areas, some of them clearly emaciated, trying to feed,” Calambokidis said.
The whales are reported having little body fat, which leads experts to suspect the event was caused by dwindling food sources, impacted by the rapidly warming waters of the northern Bering Sea and Chukchi Sea in Alaska.
Scientists say the warming temperatures is a consequences of climate change, which is helping to melt ice in the Bering and Chukchi seas to record lows.
“The Arctic is changing very, very quickly, and the whales are going to have to adjust to that,” Sue Moore, a University of Washington oceanographer, told Reuters.
Moore says the lack of sea ice may be reducing the supply of tiny crustaceans called amphipods, which are the gray whales primary food source.
Gray whales travel to Alaska in the summer to consume the food necessary to survive the migration south towards Mexico and without the necessary nutrients it would be difficult to survive the trip.
Other scientists however, have a different theory. David Weller, a biologist at Southwest Fisheries Science Center in San Diego, believes the whales have reached a population capacity. He says the current population of North Pacific gray whales is now 27,000, the highest number documented by the agency since it started recording data in 1967.
“Keep in mind that carrying capacity is not a hard ceiling, but that it’s a shifting threshold,” Weller said, according to Reuters. “In some years or period of years the environment is capable of supporting more whales than in other years.”
Reuters says the last major West Coast gray whale die-off occurred in 1999 and 2000 when El Nino caused ocean waters to heat up dramatically.