Beluga and Narwhal: Monodontidae

Beluga whales and narwhals are the only two living species in this family. Although they look quite different, these species share certain physical characteristics, including a very small beak and small head. Their neck bones (cervical vertebrae) are not fused or joined together, giving them the ability to turn their head without turning their entire body. Neither species has a dorsal (back) fin, only a ridge where the fin normally is found. The lack of a fin is unusual in whales. Members of this family range in size from 13 to 16 feet (4 to 5 meters) and in weight from 1,500 to 3,500 pounds (680 to 1,600 kg).

Both species change color as they age. Belugas are born gray, but gradually become white by the time they reach maturity at seven to nine years. Narwhals are born gray. As young animals, they become almost completely blue-black. In adulthood they become mottled (spotted) dark gray, with more dense splotches on the back and less dense ones on the belly. In old age, they become white.

The main difference in these species is in their teeth. Belugas have simple teeth in both the upper and lower jaw. Narwhals have only two teeth in the upper jaw. In females, these teeth do not erupt or become visible. In males, one tooth becomes a spiraled tusk that may be 10 feet (3 meters) long.