Since 2019, the carcasses of 332 gray whales have washed up on beaches in the Western United States. One-hundred-and-thirty-five deaths occurred in Alaska, prompting the National Oceanic and Atmospheric Administration (NOAA) to declare an “unusual mortality event.” However, there is good news this year. The gray whale deaths have tapered off, and biologists believe the population might be recovering.
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, leading to reduced productivity. Primary productivity in the northern Bering Sea declined by 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shallow ecosystem favored large communities of benthic amphipods (the favorite food of gray whales), but it has now been replaced by an ecosystem dominated by zooplankton, such as krill.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 amount of fatty acids the whales need to build adequate blubber.
Biologists estimate that one-quarter to one-third of the West Coast’s gray whale population has died in recent years. The dead whales appeared extremely emaciated, and researchers think there were too many whales for the amount and type of food they could find to eat as the oceans warm and the environment changes. However, this die-off was not a novel situation. Gray whales suffered a previous mortality event over two decades ago and slowly recovered.
This year, researchers counted more gray whale calves than in the previous few years, and the whales looked healthier during their annual migration north. Only time will tell if the population is recovering, but it seems to be on the rebound.
Meanwhile, the news is not as good for humpback whales in Alaska. Four humpbacks have been found dead on Kodiak this year. The whales were extremely decomposed, leaving scientists with no clues as to the cause of their deaths.
Orca populations in Alaska appear healthy, but the endangered southern resident orcas near Puget Sound and the San Juan Islands continue to struggle. A research study in the Public Library of Science suggested that 99% of the orcas studied in the area had photographic evidence of skin lesions. Researchers evaluated photos from nearly 20,000 orca sightings from 2004 to 2016 and noted that the lesions became more prevalent.
The lesions usually appear as gray patches on the orca’s skin. Biologists don’t know what causes the lesions but fear they are a sign of continued declining health in the animals. While researchers cannot directly correlate the lesions with whale deaths, they think they are likely signs of an embattled immune system.
The southern orcas face several threats. A growing population of humans in the area where the whales live has caused more pollution. More sources of underwater noise have affected the ability of the orcas to hunt using echolocation. Increased water temperatures and solar radiation probably also stress the animals. One of the most significant factors leading to the decline of the southern orcas is the dramatic decrease in the number of Chinook salmon, the orca’s favorite food, in the area. Researchers documented a 75% drop in reported sightings of southern residents from 2004 to 2020, corresponding with a 50% decline in Chinook salmon from British Columbia’s Fraser River.
Changes in whale populations reflect the health of our oceans. Gray whales prefer to feed on benthic amphipods, but as sea ice diminishes and the environment of our northern oceans changes, benthic amphipods are on the decline. Humpback whales feed on zooplankton and small fish, but as the seas warm, zooplankton isn’t as plentiful as it once was. Orcas eat fish, but salmon and other species have declined in many areas.
The whales are telling us they don’t like their changing environment, but will we listen and do something about it?
Read more about Kodiak Wildlife in my book Kodiak Island Wildlife.
My true crime book, Murder and Mystery in the Last Frontier, is a finalist for the Silver Falchion Award for the best true-crime book of 2023. Thank you to the Readers and Writers Book Club for mentioning it in their August Newsletter.
Robin Barefield is the author of five Alaska wilderness mystery novels: Big Game, Murder Over Kodiak, The Fisherman’s Daughter, Karluk Bones, and Massacre at Bear Creek Lodge. She is also the author of the non-fiction book Kodiak Island Wildlife and the true-crime book Murder and Mystery in the Last Frontier. Sign up below to subscribe to her free monthly newsletter on true crime and mystery in Alaska, and listen to her podcast, Murder and Mystery in the Last Frontier.
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