Researchers hear calls of blue whales previously unknown to science

Blue whales are the largest animals that have ever lived. It’s therefore difficult to imagine a population of blue whales going unnoticed. But scientists have found that there are groups of blue whales living in the Indian Ocean that were previously unknown to researchers. And they have their own unique song. Salvatore Cerchio, a marine mammal biologist at the African Aquatic Conservation Fund, speaks to The World’s host Carol Hills about the new findings.