beaked whale

any of several toothed whales of the family Hyperoodontidae (Ziphiidae), inhabiting all oceans and having beaklike jaws.

[1875-80]

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▪ mammal

Introduction

 any of 21 species of medium-sized toothed whales (toothed whale) with extended snouts, including the bottlenose whales (bottlenose whale). Little is known about this family of cetaceans (cetacean); one species was first described in 1995, two others are known only from skeletal remains, and the bodies of undescribed species occasionally drift ashore.

Natural history

      In addition to the snout, beaked whales are characterized by two throat grooves that meet under the chin and by the lack of a central notch in their wide flukes. Other distinguishing features are small rounded flippers and a dorsal fin located toward the rear of the body. Ranging in length from 3.7 metres (12.1 feet) for the dwarf, or pygmy, beaked whale (Mesoplodon peruvianus) to nearly 13 metres for the giant bottlenose whale (Berardius bairdii), these mammals weigh between 1,000 and 14,000 kg (2,200 and 31,000 pounds). Colour is variable but usually consists of some combination of gray or black with white. Their bodies are often covered with scars from fighting each other and from bites of the cookie-cutter shark (genus Isistius). Males are more heavily scarred than females owing to fights with other males for mates. In some species the males have bone inside the beak that is as dense as some rocks. In almost all beaked whales, functional teeth are limited to one or two pairs present only in the lower jaw, and these usually erupt through the gums only in the male. In the strap-toothed whale (M. layardii), these two tusklike teeth are remarkable in that they curve upward out of the mouth, holding the jaws partially shut. Shepherd's beaked whale (Tasmacetus shepherdi) is unusual in having numerous small functional teeth.

      Rapid swimmers and deep divers, beaked whales are seldom seen because the structure of the head and blowhole causes their blow to be directed forward and not rise much above the surface of the water. They are found in all of the world's oceans, although certain species have limited distributions. Some are solitary or travel in small groups, but others may appear in pods of 30 or more. Groups often surface and dive in unison. Squid is their preferred prey, although most also eat fish and bottom-dwelling invertebrates. As with other whales, the stomach is complex, containing up to 14 compartments (see cetacean: Feeding adaptations (cetacean)). Although beaked whales lack the usual first compartment (forestomach), their connecting chambers, which contain up to 10 subcompartments, are more complex than those in other cetaceans.

Paleontology and classification

      Family Ziphiidae (Hyperoodontidae in some classifications) is one of the early offshoots of the toothed whale lineage, appearing about 20 million years ago in the early Miocene Epoch (23.8 million to 16.4 million years ago). Related families include dolphins (family Delphinidae) and sperm whales (family Physeteridae). There is no consensus about the relationships of the individual genera within the family.

Family Ziphiidae (beaked whales)

 21 species in 6 genera found in parts of all oceans.

      Genus Mesoplodon

 14 species found worldwide, all possessing a single pair of teeth. Bahamonde's beaked whale (M. bahamondi), first described in 1995, is known only on the basis of a damaged skull from the Juan Fernández Islands off the coast of Chile. In 2002 M. perrini was established after analysis of DNA from four dead specimens found near San Diego, California, U.S.

      Genus Berardius (giant beaked, or giant bottlenose, whales)

 2 species, one of the northern Pacific, the other of far southern seas and around Antarctica.

      Genus Hyperoodon (bottlenose whales (bottlenose whale))

 2 species, one primarily of the North Atlantic, the other of far southern seas and around Antarctica.

      Genus Indopacetus (Longman's beaked whale)

 1 Indo-Pacific species identified only from skeletons in 1926 and 1955.

      Genus Tasmacetus (Shepherd's beaked whale)

 1 species of far southern seas and around Antarctica.

      Genus Ziphius (Cuvier's beaked, or goose-beaked, whale)

 1 species of temperate and tropical waters.

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