Odontoceti - the toothed whales

The presence of teeth and one external blowhole distinguishes toothed whales from baleen whales. With the exception of the 12 species of baleen whales, all other cetacean species have teeth. Nearly 90 percent of cetacean species are toothed whales. Most toothed whales are small dolphins and porpoises. However there are a few large toothed whales such as the killer whale and the sperm whale, which grow up to 18.3m in length.

Toothed cetaceans commonly found in arctic and sub-arctic waters include the narwhal, beluga, and killer whale. Other toothed whales, dolphins and porpoises can are also be seen in northern waters.

Most Odontocetes use echolocation to locate food. A series of low-frequency clicks called a train passes through a fat-filled organ in the head, called a melon, which focuses the sound wave. The train of clicks is focused into a beam that bounces off objects and reflects back to the whale. The echoed sound waves are received in the fat-filled cavities of the lower jawbone and conducted through the bone to the ear and the brain, where the information is interpreted. Through the echoes the whale can determine distance to an object, its size, shape and its texture, creating a sound picture of its environment.

Dolphins and porpoises are easy to confuse. One important way to distinguish them is that porpoises have spade-shaped teeth, and dolphin teeth are conical or rounded. Members of the dolphin, or Delphinidae family, usually have teeth in both jaws, a melon-shaped head with a distinct snout called a beak, and a dorsal fin.

Members of the porpoise, or the Phocoenidae family, have blunt heads and small spade-shaped teeth. Porpoises grow up to 2.1m in length and lack the beak and melon-shaped foreheads of most dolphin species. Porpoise species found in arctic and sub-arctic waters include the harbour porpoise and Dall's porpoise.