Sperm Whale

Physeter catodon

Description

The sperm whale, Physeter catodon, is a large, robust, toothed whale with a massive square head equal to one-third of the body length. Males range in length from 40-60 ft (12-18 m) and may weigh up to 58 tons (65 metric tons). Females are smaller in length and weight, about 30 ft ( 9 m) and 20 tons (22 metric tons). A narrow lower jaw closes the mouth, which contains 20-24 conical teeth. Coloration is dark or brownish gray, grading to light gray or white beneath, particularly around the jaw. The S-shaped blow-hole is located on the front and to the left of the snout, rather than on top. The dorsal fin varies in shape from a strongly defined triangle to a low hump. The skin has a prune-like texture overall.

A reservoir in the whale's head, containing oil and once thought to hold sperm, gave the whale its name. Many taxonomists now prefer the classification Physeter macrocephalus. Herman Melville's Moby Dick was a sperm whale.

Behavior

The sperm whale exhibits a complex social organization that is not well understood. Scientists have noted two types of schools, each comprising up to about 50 animals-bachelor schools made up of un-mated bulls, and nursery schools composed of cows and nursing calves. During breeding season, males compete for control over breeding females and establish harems of about ten cows. The gestation period is 16 months, after which a single calf is born, 13 ft (4 m) long and weighing nearly a ton (0.9 metric tons).

Sperm whales follow schools of squid and octopus to great depths, routinely diving 1,500 ft (450 m) below the surface and possibly diving 10,000 ft (3,000 m) on occasion. A variety of fishes, such as sharks, rays, skates, and bony fishes are also eaten.

Habitat

The sperm whale is a creature of the open ocean and deep oceanic canyons. It ranges from the edges of both polar ice caps to the equator, breeding in the warmer latitudes and migrating to cooler latitudes. Large males cover greater distances and travel furthest to reach the edges of the polar ice.

Distribution

Historically, the sperm whale was found throughout the world's oceans, concentrated mostly in the middle latitudes. The population once numbered in the millions, making it the mainstay of the whaling industry.

Although the population has been greatly reduced by whaling, the sperm whale is considered the least threatened of the great whales. Current population estimates range from 700,000 to nearly 2 million.

Threats

The sperm whale was one of the earliest targets of whalers and was hunted for centuries, primarily for spermaceti oil taken from an organ in the nose. This oil, which allows whales to decompress after deep dives, was used in oil lamps and for lubrication. In addition to oil, the mammal was valued as the source of ambergris, a waxy secretion used in the fabrication of perfumes because of its ability to hold scent. The sperm whale has been commercially hunted since the 11th century reaching its peak in 1820-1860 and again in 1960-1962 when new technologies assisted in taking 67,000 individuals in only two years.

Conservation and Recovery

Restrictions were first placed on hunting of sperm whales at the International Conference on Whaling convened by the League of Nations in 1937. Quotas and size restrictions were established to protect females and assure future breeding stock. When large bulls were taken, however, the fertility rate of harems declined precipitously.

By the late 1970s conservation groups, alarmed by the continuing decline of the sperm whale, pressured government members of the International Whaling Commission (IWC) to greatly reduce fishing quotas for the sperm whale. As a result, factory-ship whaling, using floating meat and oil processing plants, was banned. Soviet whaling was severely curtailed, and the Japanese agreed to take only minke whales in Antarctic waters. Hunting quotas for the sperm whale were established in the low thousands at that time.

In 1986, the IWC declared a moratorium on the killing of whales, except for the purposes of scientific research, a ban that has more or less been observed by all 38 member countries.

Contacts

Office of Protected Resources
National Fisheries Service
1315 East-West Highway
Silver Spring, Maryland 20910

U.S. Fish and Wildlife Service
Division of Endangered
Species Mail Stop 420 ARLSQ
1849 C St., N.W., Washington, D.C. 20240

References

Baker, M. L. 1987. Whales, Dolphins, and Porpoises of the World. Doubleday, Garden City.

National Marine Fisheries Service. 1991. Recovery Plan for the Northern Right Whale (Eubalaena glacialis ). Right Whale Recovery Team, National Marine Fisheries Service, Silver Spring, MD.

Norris, K. S., and G. W. Harvey. 1972. "A Theory for the Function of the Spermaceti Organ of the Sperm Whale." In Animal Orientation and Navigation. NASA, Washington, D.C.

sperm whale • n. a toothed whale of the family Physeteridae (esp. the very large Physeter macrocephalus), with a massive head, typically feeding at great depths on squid, formerly valued for the spermaceti and sperm oil in its head and the ambergris in its intestines.

sperm whale Largest of the toothed whales. It has a squarish head and feeds on squid and cuttlefish. Species Physeter catodon.

sperm whale (Physeter catodon) See PHYSETERIDAE.