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  The Mammals of Texas - Online Edition

Sperm Whale
Order Cetacea : Family Physeteridae : Physeter macrocephalus Linnaeus

Sperm Whale (Physeter macrocephalus).  Illustration by Pieter A. Folkens.Description. A large, blackish-brown whale with huge head and truncate snout; lower jaw small, long, and slender, the symphysis extending half the length of rami; the single blowhole on anterior left edge of snout; no dorsal fin, but conspicuous hump; eye very small, low, and near angle of mouth; pectoral fin short and relatively broad; upper jaw lacking functional teeth; lower jaw with 22-24 large, sharp teeth on each side. Total length of males, up to 20 m; females much smaller. Weight of a male 13 m long, 39 metric tons.

Distribution in Texas. Sperm whales are worldwide in distribution and occur in all oceans, including Arctic and Antarctic waters, but are primarily found in temperate and tropical waters of the Atlantic and Pacific Oceans. Sperm whales are the most numerous of the great whales in the Gulf of Mexico and sightings near the Texas coast are relatively common. They are classified as "endangered."

Habits. Sperm whales are highly migratory, especially the males. Adult males move into high latitude temperate waters during summer, leading a solitary lifestyle, while females remain grouped in tropical or subtropical waters. In winter, the bulls return to lower latitudes for mating.

These whales regularly dive to depths of 1,000 m but are known to reach depths of over 2,100 m and may be capable of dives to 3,000 m. At such depths these remarkable animals hunt their primary prey — squid. Much speculation has arisen concerning the feeding method of sperm whales as no light penetrates to the depths these whales dive, and squid are highly elusive swimmers. The whales may feed by ambushing prey as they lie relatively motionless near the ocean floor, attracting squid with a bioluminescent glow emanating from their mouth, or perhaps by stunning prey with ultrasonic sounds. Due to the great depths at which these animals feed, the exact method of the sperm whale’s feeding habits has yet to be determined. These whales are known to produce a variety of "click sounds" occurring in sequence and termed "codas." Such sounds are probably used in echolocation and may play an important role in locating prey while feeding.

Up to 1 metric ton of squid per day is required to sustain a single sperm whale. Other than squid, these whales occasionally consume other deepwater prey including octopus, lobsters, crabs, jellyfish, sponges, and several varieties of fish.

Breeding behavior in sperm whales is similar to harem formation — a single, dominant male accompanies a group of females and defends the group against competing males. During this time, smaller males are driven off to form their own "bachelor groups" and battles between rival males for control of the harem may occur. Twenty to thirty females may comprise a harem but many of them may already be pregnant or tending young. The gestation period is approximately 15 months, the period of lactation is 1-2 years, and there is a "resting period" of up to 10 months following weaning before the females will mate again. The breeding cycle therefore, may take as long as 5-7 years.

Newborn sperm whales are about 4 m in length and weigh approximately 1 metric ton. Although twin calves are known, a single calf per female is believed the rule. Sexual maturity is reached at about 10 years of age.

Sperm whales were once the mainstay of the pelagic whaling industry. Prior to the advent of cannon harpoons, diesel-powered catcher boats, and massive factory ships, the hunting of sperm whales was a dangerous occupation. Sperm whales are known to have effectively fought back on occasion — one even sank an American whaler, the Essex, in 1820. In spite of the danger, sperm whales were hunted the world over for the array of valuable products these whales contained — whale oil for lamps and lubricants; spermaceti (oil from the forehead) for high quality, smokeless candles; and ambergris, a waxy by-product of digestion which was used in the manufacture of fragrances. By the early twentieth century, whaling had become an efficient, "wide open" business that threatened not only the sperm whale, but all of the great whales, with extinction. Finally, in the 1970s whaling was banned worldwide.

Illustration credit: Pieter A. Folkens.