Science, Tech, Math › Animals & Nature 10 Facts You Should Know About Whales, Dolphins, and Porpoises Share Flipboard Email Print skeeze/Pixabay Animals & Nature Marine Life Marine Life Profiles Marine Habitat Profiles Sharks Key Terms Amphibians Birds Habitat Profiles Mammals Reptiles Wildlife Conservation Insects Forestry Dinosaurs Evolution View More By Jennifer Kennedy Marine Science Expert M.S., Resource Administration and Management, University of New Hampshire B.S., Natural Resources, Cornell University Jennifer Kennedy, M.S., is an environmental educator specializing in marine life. She serves as the executive director of the Blue Ocean Society for Marine Conservation. our editorial process Jennifer Kennedy Updated August 05, 2019 The term "whales" can include all cetaceans (whales, dolphins, and porpoises), which are a diverse group of animals ranging in size from just a few feet long to over 100 feet long. While most whales spend their lives offshore in the ocean's pelagic zone, some inhabit coastal areas and even spend part of their lives in freshwater. Whales Are Mammals Whit Welles Wwelles14/Wikimedia Commons/CC BY 3.0 Whales are endothermic (commonly called warm-blooded). Their body temperature is about the same as ours, even though they often live in cold water. Whales also breathe air, give birth to live young, and nurse their young. They even have hair! These characteristics are common to all mammals, including humans. There Are Over 80 Whale Species Betty Wiley/Getty Images Actually, 86 species of whales are currently recognized, from the tiny Hector's dolphin (at about 39 inches long) to the gigantic blue whale, the biggest animal on Earth. There Are Two Groups of Whales Jayanarayanan Vijayan/EyeEm/Getty Images Out of the 80-plus species of whales, about a dozen of them feed use a filtering system called baleen. The rest have teeth, but they're not teeth like we have — they are cone-shaped or spade-shaped and are used to catch prey, rather than for chewing. Since they are included in the group of toothed whales, dolphins and porpoises are also considered whales. They're the Biggest Animals in the World Franco Banfi/Getty Images The order Cetacea contains the two largest animals in the world: the blue whale, which can grow to about 100 feet in length, and the fin whale, which can grow to about 88 feet. Both feed on relatively tiny animals, such as krill (euphausiids) and small fish. They Rest Half Their Brains While Asleep Gabriel Barathieu/Wikimedia Commons/CC BY 2.0 The way whales "sleep" may sound strange to us, but makes sense when you think of it like this: whales cannot breathe underwater, which means they need to be awake just about all the time to come up to the surface when they need to breathe. So, whales "sleep" by resting one half of their brain at a time. While one half of the brain stays awake to make sure the whale breathes and alerts the whale to any danger in its environment, the other half of the brain sleeps. They Have Excellent Hearing Salvatore Cerchio et al. / Royal Society Open Science/Wikimedia Commons/CC BY 4.0 When it comes to senses, hearing is the most important to whales. The sense of smell isn't well-developed in whales, and there is a debate about their sense of taste. But in the underwater world where visibility is highly variable and sound travels far, good hearing is a necessity. Toothed whales use echolocation to find their food, which involves emitting sounds that bounce off whatever is in front of them and interpreting those sounds to determine the object's distance, size, shape, and texture. Baleen whales probably don't use echolocation, but use sound to communicate over long distances and may also use sound to develop a sonic "map" of the ocean's features. They Live a Long Time Bering Land Bridge National Preserve/Wikimedia Commons/CC BY 2.0 It is nearly impossible to tell the age of a whale just by looking at it, but there are other methods of aging whales. These include looking at earplugs in baleen whales, which form growth layers (kind of like the rings in a tree), or the growth layers in the teeth of toothed whales. There is a newer technique that involves studying aspartic acid in the whale's eye, and is also related to growth layers formed in a whale's eye lens. The longest-living whale species is thought to be the bowhead whale, which may live to over 200 years old! Whales Give Birth to One Calf at a Time NOAA Photo Library/Flickr/CC BY 2.0 Whales reproduce sexually, meaning it takes a male and a female to mate, which they do belly-to-belly. Other than that, there's not much known about the reproduction of many whale species. Despite all our studies of whales, reproduction in some species has never been observed. After mating, the female is generally pregnant for about a year, after which she gives birth to one calf. There have been records of females with more than one fetus but usually, only one is born. Females nurse their calves. A baby blue whale may drink over 100 gallons of milk a day! Whales need to protect their calves from predators. Having only one calf allows the mother to focus all her energy on keeping her calf safe. They're Still Hunted Hulton Archive/Stringer/Getty Images While the heyday of whaling ended long ago, whales are still hunted. The International Whaling Commission, which regulates whaling, allows whaling for aboriginal subsistence purposes or scientific research. Whaling occurs in some areas, but whales are threatened even more by ship strikes, entanglements in fishing gear, fisheries bycatch, and pollution. Whales Can Be Viewed From Land or Sea Tim Clayton - Corbis/Contributor/Getty Images Whale-watching is a popular pastime along many coasts, including California, Hawaii, and New England. Across the world, many countries have found that whales are more valuable for watching than hunting. In some areas, you can even watch whales from land. This includes Hawaii, where humpback whales can be seen during the winter breeding season, or California, where gray whales can be seen as they pass along the coast during their spring and fall migrations. Watching whales can be an exhilarating adventure, and a chance to see some of the world's largest (and sometimes most endangered) species.