Whales are marine mammals which live their whole lives underwater.

The scientific term cetacean is used to describe the 78 known species of whales dolphins and porpoises (order Cetacea) Cetaceans can be further divided into three suborders: the toothed whales or Odontoceti; baleen whales or Mysticeti; and extinct whales or Archaeoceti.

ODONTOCETI — The toothed whale — All of the dolphins and porpoises and most of the smaller whales are toothed whales that feed primarily on fish and invertebrates like squid and crustaceans. Only one toothed whale, the sperm whale, grows very large (and was one of the most keenly valued by whalers).

MYSTICETI — The baleen whale — Instead of teeth, these whales' jaws hold two huge sets of bristly baleen strips, 160 to 360 on a side, which the whale uses like a huge strainer to catch his dinner of small sea animals called plankton, or krill. When feeding, the whale swims with his mouth open, taking in huge quantities of krill laden water. He then closes his mouth and, with his giant tongue, forces the water through the baleen sieve, leaving a layer of plankton on the overlapping plates. Whales can eat up to eight tons of plankton a day.

Baleen whales are subdivided into three families:

• 1. Right Whales (family Balaenidae):Right whales have long arched jaws with long baleen plates. They are slower than the rorqual whales and have no dorsal fin or ventral grooves.
• 2. Rorqual Whales (family Balaenopteridae). The rorqual is streamlined and fast, with a dorsal fin and ridges or pleated ventral grooves under the throat. Because of their speed, the rorqual were not primarily hunted until the arrival of steamwhalers
• 3. Gray Whale family Eschrichtiidae) .

Whales are adapted for swimming and diving. Their thick layer of blubber provides insulation, buoyancy and stores energy. The whale's lungs and blood can store oxygen so effectively that a balelen whale can hold it's breath for up to 50 minutes, whereas the sperm whale can do it up to 75 minutes. Sperm whales can dive to depths of 1,500 feet below the surface in search of prey, the giant squid.

Because of extensive whaling up until 1966, Today's whale populations are severely diminished from their pre-whaling numbers. In 1946 the International Whaling Commission (IWC) was formed to regulate whaling on a international basis, but large-scale commercial whaling continued until a 1966 IWC moratorium.

Today, seven species of cetaceans in the U.S are on the endangered species list: blue, bowhead, fin, humpback, right, sei and sperm.