One-hundred-seventy-one gray whales have washed up on Pacific beaches from Mexico to Alaska so far this year. Seventy-eight whales were spotted off the coast of Mexico, 85 in U.S. waters, and eight near Canada. Of the whales found along the U.S. Pacific Coast, 37 dead whales were spotted in California, five in Oregon, 29 in Washington, and 14 in Alaska. Since most whales sink to the ocean floor when they die, the 171 recovered carcasses probably represent only a fraction of the number of gray whales that have died on their northward migration this spring and summer.
In my last post, I wrote about tufted puffins dying on the Pribilof Islands in the Bering Sea, and I explained how their deaths are likely linked to the warming ocean temperatures in the Bering Sea. It comes as no surprise to learn puffins aren’t the only animals affected by warming water temperatures and melting sea ice. From the smallest zooplankton to the most massive whales, all animals in the region are feeling the impact of climate change.
Gray whales have one of the longest migrations of any mammal. In the summer they feed in the Arctic in the Bering, Chukchi, and Beaufort Seas, and in the fall, they migrate to their calving grounds in the southern Gulf of California and Baja Mexico, a migration of 5000 to 7000 miles (8,050 – 11,275 km) each way. Their average swimming speed is only 3 to 5 mph (5-8 km/hr), so this migration takes a long time.
The known deaths of 171 whales have induced the National Oceanic and Atmospheric Administration (NOAA) to declare an “unusual mortality event” and launch an investigation to determine why the whales are dying. Necropsies of the whales indicate most have starved to death. Ship strikes killed four found in San Francisco Bay, and since gray whales don’t usually enter this area, researchers assume these animals were stressed and perhaps searching for food.
Investigators aren’t sure why the whales are starving, but they think it’s possible the gray whale population has exceeded its carrying capacity under current conditions. In other words, there are too many gray whales and not enough food.
We know gray whales have been impacted by ocean warming in recent years. During the summer of 2018, waters in the Bering Sea soared nine degrees warmer than average. These increasing seawater temperatures have reduced winter ice cover in the region, which has led to a reduction in productivity. Primary productivity in the northern Bering Sea declined 70% from 1988 to 2004. This previously ice-dominated, shallow ecosystem favored large communities of benthic amphipods (the favorite food of gray whales), but it has now been replaced by an ecosystem dominated by smaller species of zooplankton, such as krill. Gray whales have responded by migrating further north to the Chukchi Sea, but amphipods might now be disappearing from this region as well, forcing gray whales to consume less nutritious krill, and krill might not contain the percentage of fatty acids the whales need to build adequate blubber.
Scientists expect to find more dead gray whales this summer, and one was recently washed up on a beach on Kodiak Island. NOAA continues to monitor the mortality event and posts updates on this website.
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Robin Barefield is the author of three Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter. To download a free copy of one of her novels, watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.
Great articles on the king crab and grey whales. I learned a lot
We think of the great trips we had bear viewing with you and Mike all the time. They really were adventures of a lifetime.