Since the 1980s, there has been a mass die-off of whales on the Pacific coast. Experts were baffled as to why the whales were turning up dead on the shore, and after decades of research, a new study suggests a possible reason behind it.
Gray Whales Mass Die-Off
Scientists now think they know why almost 2,000 gray whales have been found dead off the Pacific coast, linked to three inexplicable large die-off occurrences. Gray whale populations had previously achieved a remarkable recovery from the verge of extinction following the International Whaling Commission's blanket ban on commercial whaling in 1986.
But since then, several enigmatic mass extinctions of beautiful marine creatures have been seen, and a growing body of study has linked these events to climate change. Since the gray whale population expanded after the prohibition, marine scientists have hypothesized that the fatalities were a natural consequence as their expanding numbers reached a new equilibrium throughout the northern Pacific food web.
Coastal crustaceans, including shrimp and scuds, are the whales' preferred food, and recent "unusual mortality events" may result from declining Arctic ice, according to a new study. As their environment vanishes beneath them, it appears as though these thousands of gray whales starved to death.
The US Marine Mammal Stranding database maintained by the National Oceanic and Atmospheric Administration (NOAA) allowed researchers to more easily monitor and identify trends in gray whale mortality recorded since 1990.
Between 1999 and 2000, the second big die-off had a more accurate mortality toll of 651 whales. Every time a die-off occurred, the gray whale population fell by 15 to 25 percent.
The most concerning mass die-off episode, which started in 2019 and is still going strong as of September 26, 2023, is the most recent and longest; to date, 688 whales have perished.
About 70 gray whales were discovered dead over six months in 2019, which sparked public alarm and necropsies on Californian beaches by volunteers and scientists from the California Academy of Sciences.
Reasons Behind The Gray Whale Mass Die-Off
According to Stewart's research, the first two die-offs were directly related to the seasonal expansion of Arctic sea ice, which at the time kept rising whale populations from their feeding sites. However, the scientists found a new cause for the lengthier die-off episode that started in 2019 - diminishing Arctic sea ice has weakened the food chain that gray whales depend on.
First, the loss of the green algae that develop on the undersea face of the ice has resulted in smaller and less thriving colonies of coastal crustaceans like shrimp and scuds, the principal food source for gray whales.
The timing of the melting of the arctic sea ice, which the researchers had noted, was mapped out by NOAA's National Snow and Ice Data Center (NSIDC) to the decline in crustacean populations.
The population of gray whales was approximately 25,000 at its peak of recovery, but due to die-offs and low birthrates, the population is currently just 14,500 and is declining, according to the researchers.
According to Stewart, the Arctic Ocean may no longer be able to sustain 25,000 gray whales as it once did due to severe warming.
However, according to a marine study, the extensive evolutionary history and intelligence of the gray whale species as a whole provide some hope.
The marine mammal has weathered Ice Ages and other environmental upheavals for hundreds of thousands of years, indicating that the likelihood of total extinction is quite low.
Stewart added that there is no danger of the extinction of gray whales due to climate change. However, we need to consider these developments' potential future implications carefully.
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