Researchers have found that changing Arctic conditions are the likely culprit to three major North Pacific gray whale population mortality events since the 1980s.
Sadly, during each of the die-off events, including the one that began in 2019, the whale population was reduced by up to 25%, putting enormous pressure on its members.
The research was published in the journal Science and highlights the fact that, on the one hand, Pacific gray whales are one of the few large whale species that have managed to recover their populations to pre-commercial whaling numbers. However, they are likely to become more susceptible to changing environmental conditions.
According to Joshua Stewart, the study’s lead author and assistant professor with Oregon State University’s Marine Mammal Institute:
“These are extreme population swings that we did not expect to see in a large, long-lived species like gray whales. When the availability of their prey in the Arctic is low, and the whales cannot reach their feeding areas because of sea ice, the gray whale population experiences rapid and major shocks. Even highly mobile, long-lived species such as gray whales are sensitive to climate change impacts. When there are sudden declines in the quality of prey, the population of gray whales is significantly affected.”
“It turns out we didn’t really know what a healthy baleen whale population looks like when it isn’t heavily depleted by human impacts. Our assumption has generally been that these recovering populations would hit their environmental carrying capacities and remain more or less steady there. But what we’re seeing is much more of a bumpy ride in response to highly variable and rapidly changing ocean conditions.”
You can find the original research here.