Classification
Sperm Whale, largest of the toothed whales make up the family Physeteridae of the suborder Odontoceti, order Cetacea. It is classified as Physeter catodon. The Pygmy Sperm whale is classified as Kogia breviceps, and the Dwarf Sperm whale as Kogia simus.
Appearance
Sperm whales have a huge head—up to one-third the length of the body—which houses the spermaceti, a light oily fat that is believed to aid the animal in sending a directional beam of echolocation clicks from its snout. Below the head is a relatively small and thin lower jaw, which contains a set of cone-shaped teeth that fit into sockets in the upper jaw. The bodies of sperm whales are laterally compressed, with a single blowhole on the left front of the head and a thick dorsal hump originating at the hindmost third of the body. There is a section of distinctive wrinkled skin behind the head. The body is dark gray or black, but the lips are white and there are whitish spots on the belly. There is a large difference in size between the sexes, with mature females growing to about 12 m in length, and mature males growing to about 18 m.
Diet
Sperm whales feed on fishes and particularly on large deep-water squid. According to one hypothesis, the loudest of their vocalizations, sharp clicks, may be loud enough to stun their prey and thereby facilitate feeding.
Behavior
 The whales routinely dive deeper than 1 km (deeper than 0.6 mi.) while feeding on squid, and they commonly remain submerged for 45 to 60 minutes at a time. After a long dive, sperm whales must stay at the surface for about 12 to 15 minutes, respiring (blowing) constantly to replenish their oxygen stores. Sperm whales generally travel in groups of mixed species composed of adult females with sub-adults and calves of both sexes. These groups can be as large as 50 individuals, but they usually include only about 12 animals. However, because the clicks that the whales use to communicate can be heard for at least 10 km (at least 6 mi.), the social unit may actually consist of several groups in an area that keep in touch through sound. Their communication includes a different sequence of clicks, or coda, for each individual, and it is likely that these distinctive codas are a means by which individuals recognize one another.
Breeding
Adult males usually travel in all-male groups or, more rarely, alone, joining the female-based groups for short periods in order to mate. Large males probably compete with one another for access to female groups, and females may choose particular males, probably on the basis of size. Gestation of the single young takes 15 to 16 months—probably the longest gestation period for any cetacean. Nursing can last for several years while the calf grows and learns to hunt.
 
 

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