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New research highlights “boom-and-bust” population cycles among gray whales, driven by changing Arctic conditions. Since the 1980s, three major die-offs in the eastern North Pacific gray whale population have been observed. These die-offs, including an ongoing one since 2019, have rapidly reduced the gray whale population by up to 25% in just a few years.

Gray Whales at risk of climate change effects

A study led by Dr. Joshua Stewart from Oregon State University’s Marine Mammal Institute reveals surprising population fluctuations in gray whales. These fluctuations occur when their Arctic prey is scarce, and sea ice obstructs their feeding areas. This suggests that even resilient, long-lived species like gray whales are vulnerable to climate change effects.

Researchers suggest that Eastern North Pacific gray whales, having recovered from commercial whaling, are approaching their Arctic feeding areas’ carrying capacity, making them susceptible to environmental changes from resource competition. Notably, two die-offs in the 1980s and 1990s due to harsh Arctic conditions were temporary, as the whale population quickly rebounded when conditions improved.

Baleen whale populations experience fluctuations due to climate change

Dr. Stewart suggests that our understanding of healthy baleen whale populations is flawed. Instead of stabilizing at carrying capacities, they experience fluctuations due to changing ocean conditions, challenging prior assumptions of population recovery after human impact depletion.

Approximately 14,500 eastern North Pacific gray whales undertake a remarkable 12,000-mile annual migration along the Pacific Coast, traveling from Baja California, Mexico, in the winter to the Arctic’s cold, nutrient-rich waters for summer feeding. The National Oceanic and Atmospheric Administration Southwest Fisheries Science Center in California has been studying these whales since 1967, making them one of the most extensively researched large whale populations globally.

Dr. Dave Weller from the Southwest Fisheries Science Center highlights the importance of their long-term research in understanding climate change’s impact on these iconic whales.

Shorter Arctic ice periods, driven by climate change, may initially benefit the whales, but it’s unsustainable. Their primary food source, benthic amphipods, depends on sea ice. Less ice means less food for them, leading to smaller crustaceans in warmer waters and reduced habitat for whale prey.