Whales are a diverse group of fully aquatic marine mammals classified under the infraorder Cetacea, which includes baleen whales (Mysticeti) and toothed whales (Odontoceti). They are closely related to hippopotamuses, having diverged about 54 million years ago. Baleen whales have plates of baleen for filtering krill and plankton, while toothed whales possess conical teeth for catching fish and squid. Whales can vary greatly in size, from the small dwarf sperm whale to the massive blue whale, the largest animal ever known.
These mammals are warm-blooded and must surface for air, with some species capable of holding their breath for up to 90 minutes. Whales communicate using a range of vocalizations, including the famous songs of humpback whales. Most prefer colder waters and migrate to spawn, with females typically bearing the sole responsibility for raising their young.
Historically hunted, whales are now protected by international laws, although threats from bycatch and pollution persist. They hold cultural significance in various societies and have been featured in literature and film. Whale watching has become a popular form of tourism worldwide.
