The sperm whale (Physeter macrocephalus), or cachalot, is the largest of the toothed whales. 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. Mature males average at 16 metres (52 ft) in length but some may reach 20.5 metres (67 ft), with the head representing up to one-third of the animal's length.
The sperm whale 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 echolocation and communication, may be as loud as 230 decibels (re 1 µPa at 1 m) underwater, making it the loudest sound produced by any animal. It has the largest brain of any animal on Earth, more than five times heavier than a human's. Sperm whales can live for more than 60 years.
The sperm whale can be found anywhere in the open ocean. Females and young males live together in groups while mature males live solitary lives outside of the mating season. The females cooperate to protect and nurse their young. Females give birth every four to twenty years, and care for the calves for more than a decade. A mature sperm whale has few natural predators. Calves and weakened adults are taken by pods of orcas.
From the early eighteenth century through the late 20th the species was a prime target of whalers. The head of the whale contains a liquid wax called spermaceti, from which the whale derives its name. Spermaceti was used in lubricants, oil lamps, and candles. Ambergris, a waste product from its digestive system, is still used as a fixative in perfumes. Occasionally the sperm whale's great size allowed it to defend itself effectively against whalers.
The species is now protected by a whaling moratorium, and is currently listed as vulnerable by the IUCN. The sperm whale is the largest toothed whale, with adult males measuring up to 20.5 metres (67 ft) long and weighing up to 57,000 kilograms (56 long tons; 63 short tons). By contrast, the second largest toothed whale, Baird's Beaked Whale measures 12.8 metres (42 ft) and weighs up to 15 short tons (14,000 kg). The Nantucket Whaling Museum has a 5.5 metres (18 ft)-long jawbone.