Beaked whale

Beaked whales are one of the least known groups of mammals because of their deep-sea habitat and apparent low abundance. Only three to four of the 22 species are reasonably well-known. Baird's beaked whales and Cuvier's beaked whales were subject to commercial exploitation, off the coast of Japan, while the northern bottlenose whale was extensively hunted in the northern part of the North Atlantic late in the 19th and early 20th centuries. Beaked whales are moderate in size, ranging from 4.0 to 13 metres (13.1 to 42.7 ft) and weighing from 1.0 to 15 tonnes (0.98 to 14.76 long tons; 1.1 to 16.5 short tons). Their key distinguishing feature is the presence of a 'beak', somewhat similar to many dolphins. Other distinctive features include a pair of converging grooves under the throat, and the absence of a notch in the tail fluke. Although Shepherd's beaked whale is an exception, most species have only one or two pairs of teeth, and even these do not erupt in females. Beaked whale species are often sexually dimorphic – one or the other sex is significantly larger. The adult males often possess a large bulging forehead. However, aside from dentition and size, very few morphological differences exist between male and female beaked whales.