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This is a matter of concern for specialists in this species: since January 2019, around 400 gray whales have died stranded on the Pacific coasts, from Canada to Mexico, as they migrated south. A “unusual mortality event” according to scientists but which is not totally abnormal, according to them. In the early 2000s, 600 cetaceans had died without biologists being able to define a precise cause.
By studying the silhouettes of gray whales from snapshots taken by drones, scientists found that they were getting leaner with each passing year. Many suffer from malnutrition and starve to death before reaching the Mexican coast. The weakened gray whales are also more vulnerable to collisions with boats. And this winter, they were once again less numerous to arrive in the warm waters of Baja California.
How to explain this mortality? The hypothesis evoked is that of global warming. The increase in water temperature is believed to be the cause of the scarcity of feeding grounds for gray whales in the North Pacific. These mammals migrate to the Bering Sea and off the coast of Alaska in the summer, the whales feed mainly on krill and small prey which they seek in the seabed. But these fragile ecosystems are deteriorating under the effect of global warming. The cetaceans are then led to seek their food even further, which explains why they are exhausted during the return trip to the south. At present, this is still only a guess, but it is the most solid.
In Mexico, gray whales are the subject of special protection. From the 1970s, the country launched pioneering policies to protect this species decimated by hunting. The first two sanctuaries for gray whales were created in Baja California, in the coastal lagoons where they come every winter to reproduce and give birth. Thanks to this safeguarding plan, there was a spectacular recovery of the population, which reached more than 25,000 individuals, while the species had come close to extinction.