The Soviet Union hunted whales to the brink of extinction, but its scientists secretly tracked its toll

Every year, an estimated 13 million people go whale-watching around the world, marveling at the sight of the largest animals ever to inhabit Earth. It's a dramatic reversal from a century ago, when few people ever saw a living whale. The creatures are still recovering from massive industrial-scale hunting that nearly wiped out several species in the 20th century.