Every spring, gray whales migrate up the West Coast on a 12,000-mile round-trip from their calving grounds in Mexico to the Alaskan Arctic, where they feed on tiny crustaceans. Since early 2019, an unusual mortality event has reduced their population by more than 20 percent. Whales wash up severely emaciated or sometimes suffer from ship strikes or entanglements made worse by lack of food. But researchers in Washington have identified a small group of gray whales that returns to Puget Sound every year in what seems to be a survival strategy.