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. 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.
Contributions by Pcb21, UtherSRG, and Khoikhoi.