215 Gray Whales Died & Washed Ashore In 2019; Starvation, Orca Attacks & Ship Strikes Leading Causes
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When 215 gray whales washed up dead last year along the west coast of North America, researchers wondered whether the species had recovered from the commercial whaling era and become a victim of its own success—the ocean no longer capable of feeding all those gaping mouths. But a new study for the International Whaling Commission finds that despite widespread evidence of malnutrition, other factors such as ship strikes and killer whale attacks played a significant role in the gray whale deaths from Mexico to Alaska.
Further, those documented strandings are thought to represent only a fraction of the gray whales that died last year in the eastern North Pacific. “Some may be stuck in oceanic gyres,” while others may have sunk, says the study’s lead author, Stephen Raverty, a veterinary pathologist with British Columbia’s Ministry of Agriculture.
Of the dead gray whales that were found, 40 percent were adults and 46 percent were subadults, while yearlings made up 11 percent and calves three percent. Necropsies on 50 of the whales suggest that 19 died from killer whale attacks—mainly in Alaska waters—while another eight had rake marks indicative of such attacks. Ten individuals, mostly in California, had injuries consistent with vessel or propeller strikes. The exact cause of death for the rest remains unknown, although one showed evidence of past entanglement with fishing gear.
Eighty-nine of the 215 stranded whales were rated for body condition: 29 were emaciated and 38 were thin, while only 22 were in average-to-good condition. Gray whales are typically low on fat reserves during their northward spring migration, but conditions were worse last year. At least half of the live gray whales studied in Mexico showed signs of poor nutrition compared with about 10 percent in prior years.
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https://www.hakaimagazine.com/news/necropsies-unveil-more-about-mass-gray-whale-deaths/