The whales referred to as "great whales" include all of the baleen whales and one toothed whale, the sperm whale. Great whales range in size from the 30-foot minke whale to the 100-foot blue whale.

Baleen whales do not have teeth—they have plates made of a material similar to human fingernails (baleen) that hang down from the roofs of their mouths. These plates, fringed at the ends, are used to comb large amounts of water (and sometimes mud) for small creatures of numerous species, together known as zooplankton, as well as small fish. The blue whale, not only the largest baleen whale but also the largest creature ever to have lived on earth, feeds almost exclusively on a tiny, shrimp-like creature called krill.

The great whales have been the targets of aboriginal and commercial whalers for many centuries. Their blubber was rendered into oil, their meat eaten, and their baleen used, as a precursor to plastic, in corsets, umbrellas, and other items.

Sperm Whales

Sperm whales, on which Herman Melville's Moby Dick was modelled, were hunted primarily for their oil, not only from their blubber but also from their spermaceti organ. This organ, found in the sperm whale's prominent forehead and apparently used as a lens to focus the loud clicks and other sounds the whale makes, is filled with an oil that humans once used to lubricate fine watch works and other intricate devices. Sperm whale teeth were also used for scrimshaw art.

Blue, Fin, Minke, and Humpback

The family Balaenopteridae includes species such as the blue, fin, minke, and humpback whales. These species are distinguished by their streamlined shapes, their speed, their medium-length baleens, and their throat grooves, which are accordion-like pleats that expand the animal's throat when it takes in a large amount of water to filter through its baleen. These species undertake long migrations between polar feeding grounds and temperate and equatorial birthing grounds.

Northern Right, Southern Right, and Bowhead

The family Balaenidae includes the northern and southern right whales and the bowhead whale. These whales are distinguished by their huge heads (which allow them to take in large mouthfuls of water without having to expand their throats), their very long baleens, their slow swimming speeds, and their lack of prominent dorsal fins. The bowhead is exclusively Arctic in its distribution, while the right whales undertake migrations.

Gray

The family Eschrichtiidae has one species, the gray whale. Gray whales are bottom feeders, scooping up huge mouthfuls of mud to filter out tiny crustaceans. This species undertakes the longest known migration of any whale: a 10,000-mile annual round trip between the Bering Sea (Arctic) feeding grounds and Baja California Sur birthing lagoons.

Social Structure

The most stable social grouping in baleen whales is a mother and her calf. However, they also tend to gather in small, transient groups on their rich feeding grounds or in protected mating and birthing areas. The sperm whale, however, has a complex social structure: Females live in large groups, raising their young communally, while males form "bachelor herds," migrating far greater distances than females and joining the nursery groups only during the mating season. The great whales give birth to one calf at a time, usually every other year, although in some species the interval between births is longer.

Populations

Most of the great whales are endangered. Some species such as the northern right whale and the blue whale were decimated by commercial whalers and, because of habitat degradation and other human-caused factors, have not been able to recover. Some populations such as western gray whales and eastern bowhead whales number precariously few, and may also be in danger of extinction.