Sperm whale (Physeter catodon)

Sperm whales swim through deep waters to depths of 2 miles, apparently limited in depth only by the time it takes to swim down and back to the surface. Their distributions are depend upon season and sexual/social status, however they are most likely to be found in waters inhabited by squid- at least 1,000 m deep and with cold-water upswellings. Because they are so well-adapted for deep water swimming, they are in real danger of stranding when they move inshore.
Above weights are given for mature male giant sperm whales. Females only weigh about 1/3 as much as males. Males may reach 19 m while females are only 12 meters. Newborn calves measure about 4 m and are about 1/25 the weight of females.

The enormous (up to 1/3 of total body length), box-like head of Physeter catodon sets it apart from all other species. The head contains a spermaceti organ whose function is not entirely known. It may serve to focus and reflect sound or may be a cooling organ to diminish the whale's volume and its buoyancy during prolonged dives. The giant sperm whale has the largest of mammalian brains in terms of sheer mass (approximately 9 kg). The blowhole slit is S-shaped and positioned on the left side of the head. There are 18-28 functional teeth on each side of the lower jaws, but the upper teeth are few, weak and nonfunctional. The lower teeth fit into sockets in the upper jaw. The gullet of Physeter catodon is the largest among cetaceans; it is in fact the only gullet large enough to swallow a human.

The dorsal fin is replaced by a hump and by a series of longitudinal ridges on the posterior part of the back, and the pectoral fins are quite small, approximately 200 cm. long. Tail flukes are 400-450 cm. The blubber layer of the giant sperm whale is quite thick, up to 35 cm. With respect to coloration, males often become paler and sometimes piebald with age. Both sexes have white in the genital and anal regions and on the lower jaws.

Giant sperm whales are very deep divers and may stay submerged from 20 minutes to over an hour. When they surface, sperm whales typically blow 20-70 times before redescending. They produce a visible spout made by the condensation of the moisture combined with a mucous foam from the sinuses. Giant sperm whales typically swim at speeds no faster than 10 km per hour, but when disturbed they can attain speeds of 30 km per hour.

Giant sperm whales are highly gregarious and group themselves roughly by age and sex in group sizes of 100 or more individuals. Loose family groups of about 30 individuals, however, are more common. Groups are often made up of either bachelor bulls (sexually inactive males) or "nursery schools" of mature females and juveniles of both sexes. Older males are usually solitary except during the breeding season.

Sperm whales use clicking noises for echolocation, but they also make a variety of other sounds including "groans, whistles, chirps, pings, squeaks, yelps, and wheezes" (Ellis 1980). Their voices are quite loud and can be heard many kilometers away with underwater listening devices. Each whale also emits a stereotyped, repetitive sequence of 3-40 or more clicks when it meets another whale. This sequence is known as the whale's "coda."