Sperm Whale

The sperm whale (Physeter macrocephalus) is a large toothed whale (odontocete) belonging to the order Cetacea. It is the only living member of genus Physeter, and one of three extant species in the sperm whale family, along with the pygmy sperm whale and dwarf sperm whale of the genus Kogia. A marine mammal, it possesses the largest brain of any animal. Its name derives from a milky-white waxy substance, spermaceti, found in its enormous head.

A mature male can grow to 20.5 metres (67 ft) long, its head representing up to one-third of the animal's length. The largest living toothed animal, the species feeds primarily on giant and colossal squid. Plunging to 3 kilometres (9,800 ft) for prey, it is the deepest diving mammal. Its clicking vocalization, a form of sonar which may have other purposes, is the loudest sound produced by any animal.

The sperm whale is cosmopolitan, living across the oceans in groups called social units. Units of females and their young live separately from sexually mature males. The females cooperate to protect and nurse their young. Females give birth every three to six years, and care for the calves for more than a decade.

Living up to 70 years, a mature sperm whale has few natural predators. Calves and weakened adults are taken by pods of orcas. From the early 18th century through the late 20th the species was a prime target of whalers. In addition to its oil (used in lighting) and ambergris (key in perfumery), the animal's valuable spermaceti was transformed into candles, soap, cosmetics and machine oil. Occasionally the sperm whale's great size allowed it to defend itself effectively against whalers. In the most famous example, a sperm whale attacked and sank the American whaleship Essex in 1820. Diminished by whaling, the species is currently listed as vulnerable by the IUCN.

Once known as Physeter catodon, the sperm whale is also known as the common cachalot, possibly derived from an archaic French word for "tooth".