Sound is the most important sense for whales. They use it to communicate with another as well as finding their way around the oceans, and in some species to catch their prey too.
Up to now it has not been clear why different whales have evolved with different systems to hear but now scientists think they might have made a key breakthrough. Researchers from the world-renowned Smithsonian Institution in Washington think it may be to do with the different methods used by toothed whales (e.g. sperm whale), and baleen whales (e.g. blue whale), to catch their prey.
The video report below from the BBC reveals more.