Sperm Whale Flukes

The sperm whale is the largest odontocete, or toothed whale. It has been portrayed frequently in art and literature as a symbol of the great whales, and is best known as the leviathan Moby Dick in Herman Melville's novel by that name.  Sperm whales are among the deepest diving cetaceans, and are found in all oceans of the world. Females and their young travel in permanent units, whereas the much larger males rove between breeding and feeding grounds, as well as among groups of females when breeding.

PHYSICAL DESCRIPTION
The head of the sperm whale is blunt and squared off, and has a small, under slung jaw. The head is also large, and makes up to 1/3 the total body length and more than 1/3 of its mass. A single blowhole is located forward on the left side of the head, and the blow, which is bushy, is projected forward rather than straight up as it is with other whales. Its body has a wrinkled, shriveled appearance, particularly behind the head.

Sperm whales: Male sperm whales can reach a length of 18 m and 35 tons.

COLOR
The sperm whale is usually a dark, brownish gray with light streaks, spots and scratches. The skin around its mouth, particularly near the corners, is white. The ventral (underside) of the body is a lighter gray and may have white patches.

FINS AND FLUKES
The sperm whale has a squat dorsal fin, followed by knuckles along the spine. Its flippers are small and slightly tapered, while its flukes are broad, measuring as much as 16 feet (5 m) from tip to tip.

LENGTH AND WEIGHT
Adult males reach lengths of 49-59 feet (15-18 m) and weigh up to 35-45 tons (31,750-40,800 kgs). Adult females are much smaller, growing to about 36 feet (11 m) and a maximum weight of 13-14 tons (12,000-12,700 kg).

FEEDING
Its main source of food is medium-sized deep water squid, but it also feeds on species of fish, skate, octopus, and smaller squid. The diet of sperm whale populations in the open ocean includes more squid, while coastal populations mainly forage on fish. Stomach samples examined at whaling stations from whales caught in Alaska revealed that squid was an important food in the Western Aleutians and Bering Sea, but fish became progressively more important towards the eastern Aleutians and into the Gulf of Alaska. Fish eaten in northern latitudes commonly included sharks, sea devils, cod and hake.  A sperm whale consumes about one ton (907 kg) of food each day.

A sperm whale’s lower jaw contains 18-25 large teeth on each side of the jaw, 3-8 inches in length. The upper jaw may have tiny teeth but they rarely erupt. The upper jaw contains a series of sockets into which the lower teeth fit.

This is unpublished data that indicates sperm whale sightings in Alaskan waters (black dots), notice the big difference in distribution between the longline sets and the distribution of whales. Most overlap in occurring in the eastern and Central Gulfs, very little in the Bering Sea.

MATING AND BREEDING
Males reach sexual maturity at approximately 33-39 feet (10-12 m), and 10 years or more of age but do not seem to take an actual part in breeding until their late 20's. Females reach sexual maturity at 27-29 feet (8-9 m), and 7-13 years of age. Gestation is 14-16 months. Newborn calves weigh approximately 1 ton (907 kg), and are 11-16 feet (3.4-4.9 m) long. Calves nurse up to two years or longer. Contrary to earlier belief, sperm whales do not seem to have harems. Instead, large males only attend female groups a few hours at a time. These female groups (family groups) consist typically of 10-20 animals. Within these groups there appears to be communal care for the young.

Sperm Whale surfacing

DISTRIBUTION AND MIGRATION
Sperm whales are found in all oceans of the world and are widely distributed across the entire North Pacific. Females and their dependent young usually remain in tropical and temperate waters year-round, while males are thought to move north in the summer to feed in the Gulf of Alaska, Bering Sea and waters around the Aleutian Islands. The shallow continental shelf prevents their movement to areas in the northeastern Bering Sea and Arctic Ocean.  Males generally migrate south of 40º N for the winter. Only the largest mature males appear to enter the breeding grounds close to the equator.

Still, stock structure and seasonal movement is poorly understood. Historical tagging data from commercial whaling suggests that there may be considerable east-west movement in the North Pacific (between Alaskan waters and northern Japanese waters) with limited north/south movement.  Whales marked off the central and southern California coast were recovered to the north and offshore as far as British Columbia and the western Gulf of Alaska, but none were recovered north of 53º N.  And in 2001, a dead sperm whale calf was found on Kodiak Island, indicating that some females do travel into the Gulf of Alaska.

Sperm Whale rostrum (head) and blowhole

NATURAL HISTORY
The sperm whale is the deepest diver of the great whales and can descend to depths of over 3,300 feet (1000 m) and stay submerged for over an hour. Average dives are 20-50 minutes long to a depth of 980-1,970 feet (300-600 m). At such great depths there is little or no solar light. However, organisms at these depths may produce biochemical light (bioluminescence). Sperm whales use their highly developed echolocation ability to locate food and to navigate, making nearly constant clicking sounds that pulse through the water. Sperm whales communicate using "morse-code" like patterns of clicks called codas. There is also a theory that sperm whales may stun their prey with a burst of sound.

The sperm whale's head houses a large reservoir containing spermaceti, a clear liquid oil that hardens to a wax like consistency when cold, and has long been prized by whalers. Ambergris, a strange substance found in large lumps in the lower intestine of sperm whales, is formed around squid beaks that remain in the stomach. It was used in the making of perfume, and continues to be valuable in spite of its widespread replacement by synthetics.

STATUS
Sperm whales are still fairly numerous, but selective killing of the larger breeding-age males over many years upset the male-to-female ratio, and the birth rate has seriously declined in some populations. The average size of sperm whales killed noticeably decreased during the last 40 years of hunting.  Sperm whales are listed as an endangered species. The current population in the Gulf of Alaska is unknown.

Sperm whales were killed in two massive waves of commercial whaling, the Moby Dick whalers who worked mainly between 1740-1880, and the modern whalers whose operations peaked in 1964, when 29,255 were killed. Whaling took a heavy toll on sperm whales in the eastern North Pacific, including Alaskan waters, until 1986.  Most recent estimates suggest a global population of about 360,000 animals down from about 1,100,000 before whaling.

For management, the International Whaling Commission (IWC) recognizes two stocks in the North Pacific (eastern and western). However, the IWC has not reviewed this stock boundary in many years.  For the Marine Mammal Protection Act stock assessment reports, sperm whales within the Pacific U.S. Exclusive Economic Zone (EEZ) are divided into three discrete, non-contiguous areas: (1) California, Oregon and Washington waters, (2) waters around Hawaii, and (3) Alaska waters.  Genetic analyses are currently underway to examine these presumed stock boundaries.  A few recently obtained Alaska samples are being added to the analyses.  To date, the Southwest Fisheries Science Center (SWFSC) has examined boundaries for the CA/OR/WA stock, finding significant differences from animals sampled to the south but no clear picture to the west or north.

BIBLIOGRAPHY

• Folkens, P., R.R. Reeves, B.S. Stewart, P.J. Clapham, and J.A. Powell. 2002. National Audubon Society Guide to the Marine Mammals of the World. Alfred A. Knopf, New York.
• Leatherwood, S.L. and R.R. Reeves. 1983. The Sierra Club Handbook of Whales and Dolphins. Sierra Club Books, San Francisco
• Maptia, A. 1990. Whales and Dolphins. Salamander Books, London
• Whitehead, H. 2003. Sperm whales: social evolution in the ocean. Chicago, IL: University of Chicago Press

ACKNOWLEDGEMENTS

• We greatly appreciate the knowledge and assistance of Hal Whitehead of Dalhousie University and Tom Arnbom of Stockholm University, who contributed to the revision of this fact sheet.
• Illustrations courtesy Uko Gorter, Copyright © 2003, All Rights Reserved.
• Sperm whale recording courtesy Joe Olson - from National Georgraphic Television's video "Sea Monsters: Search for the Giant Squid". This special was broadcast in February 1998 and won an Emmy for Best Sound, thanks to Cetacean Research ™ hydrophones , copyright © 1997.

This material was developed from the American Cetacean Society Fact Sheet.