Before whalers discovered the treasure trove of oil that a blue whale could provide, the numbers were generous. But with the advent of 20th century whaling fleets, nearly every last one of them was killed before receiving worldwide protection in 1967. According to WWF, from 1904 to 1967, more than 350,000 were killed in the Southern Hemisphere. In 1931, during the heyday of whaling, an astounding 29,000 blue whales were killed in a single season.
