The Sperm Whale is a marine mammal species, order Cetacea, a toothed whale (odontocete) having the largest brain of any animal. The name comes from the milky-white waxy substance, spermaceti, found in the animal's head. The sperm whale is the only living member of genus Physeter. The now outdated synonym Physeter catodon refers to the same species. It is one of three extant species in the sperm whale superfamily, along with the pygmy sperm whale and dwarf sperm whale.
Historically, the sperm whale was also known as the common cachalot; "cachalot" is derived from an archaic French word for "tooth". Over most of the period from the early 18th century until the late 20th century, the sperm whale was hunted to obtain spermaceti and other products, such as sperm oil and ambergris. Spermaceti found many important uses, such as candles, soap, cosmetics and machine oil. Due to its size, the sperm whale could sometimes defend itself effectively against whalers. In the most famous example, a sperm whale attacked and sank the American whaleship Essex in 1820. As a result of whaling, the sperm whale is currently listed as vulnerable by the IUCN.
The sperm whale's unique body is unlikely to be confused with any other species. The sperm whale's distinctive shape comes from its very large, block-shaped head, which can be one-quarter to one-third of the animal's length. The S-shaped blowhole is located very close to the front of the head and shifted to the whale's left. This gives rise to a distinctive bushy, forward-angled spray.
The sperm whale's flukes are triangular and very thick. The whale lifts its flukes high out of the water as it begins a feeding dive. It has a series of ridges on the back's caudal third instead of a dorsal fin. The largest ridge was called the 'hump' by whalers, and can be mistaken for a dorsal fin because of its shape and size.
In contrast to the smooth skin of most large whales, its back skin is usually wrinkly and has been likened to a prune by whale-watching enthusiasts. Skin is normally a uniform grey in color, though it may appear brown in sunlight. Albinos have also been reported.
Females stay in groups of about a dozen individuals and their young. Mature males leave their "natal unit" somewhere between 4 and 21 years of age. Mature males sometimes form loose "bachelor groups" with other males of similar age and size. As males grow older, they typically live solitary lives. Mature males have beached themselves together, suggesting a degree of cooperation which is not yet fully understood.
The most common non-human attacker of sperm whales is the orca, but pilot whales and the false killer whale also sometimes harass them. Orcas prey on target groups of females with young, usually making an effort to extract and kill a calf. Female sperm whales repel these attacks by encircling their calves. The adults either face inwards to use their tail flukes against the orcas, or outwards, fighting with their teeth. This Marguerite formation, named after the flower, is also used by whales to support an injured unit member. Early whalers exploited this behavior, attracting a whole unit by injuring one of its members. If the orca pod is extremely large, its members may sometimes be able to kill adult female sperm whales. Large mature male sperm whales have no non-human predators, and are believed to be too large, powerful and aggressive to be threatened by orcas.
Sperm Whales usually dive between 300 to 800 meters (980 to 2,600 ft), and sometimes 1–2 kilometers (3,300–6,600 ft) to search for food. Such dives can last more than an hour. They feed on several species, notably the giant squid, the colossal squid, octopuses, and diverse fish like demersal rays, but the main part of their diet consists of medium-sized squid. Sperm whales are believed to prey on the megamouth shark, a rare and large deep-sea species discovered in the 1970s.
The sperm whale is among the most cosmopolitan species. It prefers ice-free waters over 1,000 meters (3,300 ft) deep. Although both sexes range through temperate and tropical oceans and seas, only adult males populate higher latitudes.
It is relatively abundant from the poles to the equator and is found in all the oceans. It inhabits the Mediterranean Sea, but not the Black Sea, while its presence in the Red Sea is uncertain. The shallow entrances to both the Black Sea and the Red Sea may account for their absence. The Black Sea's lower layers are also anoxic and contain high concentrations of sulphur compounds such as hydrogen sulphide.
Populations are denser close to continental shelves and canyons. Sperm whales are usually found in deep off-shore waters, but may be seen closer to shore in areas where the continental shelf is small and drops quickly to depths of 310–920 meters (1,020–3,020 ft). Coastal areas with significant sperm whale populations include the Azores and the Caribbean island of Dominica.