Using terms such as "whales," "dolphins," and "porpoises" can be misleading when people want a clear picture of how whales are related. The killer whale, for example, is actually the largest dolphin!
Scientists need to be accurate and consistent in their descriptions. That is why they use specific characteristics to classify life forms such as whales into related groups. This practice is known as taxonomy. It’s an essential tool in gaining a systematic picture of living things.
What’s the difference?
Whales: People often use the term "whale" to refer to the large animals in the group. These can be both baleen whales (the filter feeders) and toothed whales (which hunt single prey).
Dolphins: Dolphins usually have a beak and always have conical teeth that taper to a fine point.
Porpoises: Porpoises have no beak. Their teeth are flat and spade-shaped.
Whales are mammals and have many of the features and systems of mammal anatomy. For example, whales breathe with lungs, and females nurse their young on milk. But whales differ significantly from almost all other mammals—a result of their move from land to sea millions of years ago.
Whales evolved a streamlined shape, they lost their external hind limbs, and their forelimbs became flippers. Their nostrils became blowholes. Their lungs and circulatory system adapted to spending extended periods underwater.
From these changes came the remarkable, fully aquatic lives of whales.
Whales can be divided into two types by their ancestry and the way they feed—baleen whales (Mysticeti or Mysticetes) and toothed whales (Odontoceti or Odontocetes).
Baleen whales, a group that includes blue whales, are "batch feeders"—they use their plates of baleen to filter huge numbers of tiny prey out of the water.
Toothed whales such as sperm whales hunt their prey one by one. They use echolocation to find it and usually swallow it whole.
Navigating and Communicating
The ability to produce and perceive sound is important for whales—to navigate, find food, and communicate.
Toothed whales can use echolocation to hunt their prey. They send out high frequency clicks then listen for their echo as they bounce back from objects—like the next meal!
Baleen whales use low frequency sound to communicate, sometimes over considerable distances. Recent research suggests that they do this with their larynx—the ‘voice box’ in land mammals. Some baleen whales, such as male humpbacks, produce extremely complex ‘songs’.