In a sign that populations of blue whales — the largest animals on earth — are slowly recovering, scientists have documented the migration of four of the 100-foot creatures from the coast of California to waters off British Columbia and Alaska. That historic migration pattern appears to have been largely interrupted in the mid-20th century when hunting of the whales drove the giant creatures to near-extinction, leading to a ban on commercial whaling in 1965. Reporting in the journal Marine Mammal Science, U.S. and Canadian researchers said they had identified 15 blue whales off British
Columbia and Alaska based on photographs of their uniquely shaped dorsal fins and skin pigmentation patterns. Comparing those pictures with nearly 2,000 photographs of blue whales off California, researchers were able to determine that at least four of the whales found in the northern waters had also been seen off the California coast. Scientists had believed that the California and North Pacific populations were distinct, but the recent findings suggest that they may belong to one group that migrates north to feed on krill. Numbering an estimated 5,000 to 12,000 individuals, blue whales are slowly recovering but remain on endangered species lists worldwide.