Sperm Whales, Physeter macrocephalus
Taxonomy Animalia Chordata Mammalia Cetacea Physeteridae Physeter macrocephalus
Description & Behavior
Sperm whales, Physeter macrocephalus (Linnaeus, 1758), aka the giant sperm whales, may reach 20.5 m (males) in length while females reach 12 m (sexually dimorphic). 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 macrocephalus 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 sperm whale has the largest of mammalian brains, both in proportion to its body and in sheer mass (approximately 9 kg). Their blowhole 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 macrocephalus is the largest among cetaceans; it is in fact the only gullet large enough to swallow a human.
Their dorsal fin is replaced by a hump and by a series of longitudinal ridges on the posterior part of their backs, and their pectoral fins are quite small, approximately 2 m long. Tail flukes are 4-4.5 m wide. The blubber layer of sperm whales is quite thick, up to 35 cm. With respect to coloration, males often become paler and are sometimes piebald with age. Both sexes have white in the genital and anal regions and on the lower jaws. The mass of mature sperm whales ranges between 35,000-57,000 kg. Females only weigh about 1/3 as much as males.
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 descending again. They produce a visible spout made by the condensation of the moisture combined with a mucous foam from the sinuses. Sperm whales typically swim at speeds no faster than 10 kph, but when disturbed they can attain speeds of 30 kph.
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". 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."
The name Physeter is a Greek word meaning "blower," and refers to the whale's behavior of making a vapor spout when it exhales air from its lungs at the surface. The adjectival noun sperm in the vernacular name refers to the spermaceti or sperm oil obtained from the animal's head, although some have suggested that it may refer to the large size of the male's retractable penis (approximately 2 m).
The diving behavior of a medium-sized female sperm whale off the Kumano Coast, Japan, was studied using a suction-cup-attached TDR (time depth recorder) tag. The tag remained attached to the whale for 62 hours and recorded 74 dives deeper than 100 m. The whale repeatedly dived for 30-45 minutes down to 400-1,200 m. Surface intervals were generally 10 minutes between dives, except for a period of 1.3-4.2 hours spent at the surface every afternoon. The whale spent long periods of time at the bottom of dives, during which there was considerable variability in both depth and velocity data, with occasional bursts in velocity. These data suggest that sperm whales use an active search-and-pursue strategy while foraging. Assuming all dives with active bottom time were for foraging, this whale spent about 80% of its total time in foraging dives. Dives with little activity at depth were occasionally observed, which were probably for resting. Although dive parameters resemble those of northern bottlenose whales, dive profiles seem to be different, suggesting that these two deep diving cetaceans employ different foraging strategies.
World Range & Habitat
Sperm whales are found in the Atlantic, Pacific, Indian, and Arctic Oceans: sperm whales roam the deep waters of all the oceans, though they seldom approach polar ice fields and are most common in temperate and tropical latitudes. They have also be seen occasionally near coastlines in the Gulf of Mexico, where they were once quite common.
Sperm whales swim through deep waters to depths of 3,219 m, apparently limited in depth only by the time it takes to swim down and back to the surface. Their distributions 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 upwellings.
Feeding Behavior (Ecology)
Physeter macrocephalus feeds mainly on squid (including colossal squids and giant squids), octopuses and deepwater fishes, but they also prey upon sharks and skates. They are reported to consume approximately 3% of their body weight in squid per day.
Sperm whales are highly gregarious, polygamous 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. During the breeding season, breeding schools composed of 1-5 large males and a mixed group of females and males of various ages form. At this point, there is intense competition among the males for females (including physical competition resulting in battle scars all over the heads of males). Only about 10-25% of fully adult males in a population are able to breed.
Females mature sexually at 8-11 years, and males mature at approximately 10 years, although males do not mate until 25-27 years old because they usually do not have a high enough social status in a breeding school until that point. Maximum known life span is 77 years. Gestation period is 14-16 months and a single calf is born, which nurses for up to 2 years. The reproductive cycle occurs in females every 2-5 years. The peak of the mating season is in the spring in both northern and southern hemispheres so that most calves are born in the fall.
Conservation Status & Comments
Being fiercely aggressive when attacked, bull sperm whales posed a threat to small-boat whalers in the 19th century. Sperm whales were no match for modern whaling equipment, however. They have also been known to become entangled in trans-Atlantic telephone cables in dives 3/4 mile deep, but fortunately this type of incident is rare.
Sperm whales were once abundant in the Gulf of Mexico, but due to commercial whaling operations, they are seldom seen in that area now. Worldwide sperm whale populations are more stable than that of many other whales. The sperm whale is now the most abundant of the great whales because it has been hunted with less intensity than the baleen whales. Worldwide, sperm whales number about 1,500,000.
Sperm whales, Physeter macrocephalus, are classified as Vulnerable A1d on the IUCN Red List of Threatened Species:
A taxon is Vulnerable when the best available evidence indicates that it meets any of the criteria A to E for Vulnerable (see Section V), and it is therefore considered to be facing a high risk of extinction in the wild.
References & Further Research
U.S. Fish & Wildlife Service Endangered Species
Rolf Hicker Nature Photography
Whale and Dolphin Conservation Society (WDCS)
Ellis, R. 1980.The Book of Whales. Alfred A. Knopf, New York.
Harrison, R. and M. M. Brayden. 1988.Whales, Dolphins and Porpoises. Intercontinental Publishing Corporation, New York.
Lowery, G.H. Jr. 1974.The Mammals of Louisiana and Its Adjacent Waters. Kingsport Press, Inc., Knoxville, TN.
Nowak, R.M. and J.L Paradiso. 1983.Walker's Mammals of the World. 4th edition. John Hopkins University Press, Baltimore, MD.
Amano, M; Yoshioka, M, Sperm whale diving behavior monitored using a suction-cup-attached TDR tag, Marine Ecology Progress Series [Mar. Ecol. Prog. Ser.]. Vol. 258, pp. 291-295. 29 Aug 2003.
Research Physeter macrocephalus » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SCIRIS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS
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