Comparison and Contrast of Whales and Dolphins

Both dolphins and whales belong to the cetacean family and are marine animals that reside in the ocean. Some scientists even assert that dolphins are a type of whale, as the two animals have a number of shared characteristics. However, there are distinct differences between whales and dolphins as well that will teach you more about the physical appearance of these marine creatures and how they survive in their environment.

Whales and dolphins are mammals and have lungs instead of gills for breathing. They have blowholes at the tops of their heads that function like nostrils; they need to put their heads above water every so often to breathe. Both dolphins and whales have hair instead of scales, another quality that is specific to mammals. The animals have live births instead of laying eggs, and baby dolphins and whales nurse from their mothers. Whale and dolphin births take place near the surface of the water, so the young animals can easily take their first breath. Dolphins learn to swim within 30 minutes of being born, and whales can often swim at birth or shortly after.

Dolphins are part of the Odontoceti, or "toothed whale" family. This means they have cone-shaped teeth that are designed for eating squid and fish like herring and mackerel. Some whales also have teeth, but the teeth are shaped differently; for instance, the beaked whale has fang-shaped teeth in the lower part of its mouth, and the narwhal whale possesses a single tusk it uses like a tooth. Most whales have baleen in their mouths, which is a stretchy substance with small, horn-like fixtures. The baleen is positioned in a series of plates in the whale's upper jaw, filtering out zooplankton and krill. Toothed whales, on the other hand, eat fish and other sea creatures.

Most whales are considerably larger than dolphins, although some, such as the beluga whale, aren't much bigger than dolphins. An adult whale can weigh up to 200 tons and grow to be 100 feet long. The largest whale -- and largest animal -- ever to live was the blue whale, which drinks 50 pounds of its mother's milk daily while nursing, and grows up to 200 pounds each day, according to the Cool Antarctica website. Large species of dolphins, like the bottlenose dolphin, are about 10 feet long and weigh up to 400 pounds. The biggest dolphin species is the orca, otherwise known as the killer whale. Male killer whales weigh eight or nine tons, while females can reach a weight of four tons.

Both whales and dolphins rely on the sounds they make for survival, even though the sounds are utilized differently by each animal. For instance, whales make high-pitched groans and whistles to communicate with one another to warn against danger or navigate during migration. Dolphins use echolocation by making sounds from their nasal passages. The echo from the sound waves the dolphin sends out bounces back to the animal to help it find its way around in the ocean. The echolocation sound can sometimes be so piercing that it will stun other whales.