Sperm Whale Facts (Cachalot)

The sperm whale (Physeter macrocephalus) is the world's largest toothed predator and loudest animal. The whale's common name is the shortened form of spermaceti whale, and refers to the oily fluid found in the animal's head, which was originally mistaken for whale semen. The cetacean's other common name is cachalot, which derives from an ancient French word for "big teeth." Sperm whales do have large teeth, each weighing up to 2.2 pounds, but they don't actually use them for eating.

Description

Sperm whales are easily recognized by their distinctive shape, their flukes (tail lobes), and blow pattern. The whale has a large rectangular head with narrow jaw, raised ridges on its back instead of dorsal fins, and huge triangular flukes. It has an S-shaped blowhole set toward the front, left side of its head that blows a forward-angled spray when the whale breathes.

The species displays a high degree of sexual dimorphism. While males and females are the same size at birth, mature males are 30-50% longer and up to three times more massive than adult females. On average, males are about 52 feet in length and weigh 45 tons, while females are 36 feet in length and weigh 15 tons. However, there are documented reports of males measuring 67 feet long and weighing 63 tons and claims of males reaching 80 feet in length.

While most large whales have smooth skin, sperm whale skin is wrinkled. Usually it is gray in color, but there are albino sperm whales.

Sperm whales have the largest brains of any animals, either living or extinct. On average, the brain weighs about 17 pounds. Like other toothed whales, the sperm whale can retract or protrude its eyes. The whales communicate using vocalization and echolocation. Sperm whales are the loudest animals on Earth, capable of producing sounds as loud as 230 decibels. The sperm whale's head contains the spermaceti organ which produces a waxy fluid called spermaceti or sperm oil. Studies indicate spermaceti helps the animal generate and focus sound, may facilitate ramming combat, and could serve a function during whale diving.

While whales vomit most undigestible matter, some squid beaks make it to the intestine and cause irritation. The whale produces ambergris in response, much like oysters synthesize pearls.

Habitat and Distribution

Sperm whales live in oceans around the world. They prefer ice-free water that is over 3300 feet deep but will venture close to shore. Only males frequent the polar regions. The species is not found in the Black Sea. It appears to be locally extinct off the coast of southern Australia.

Diet

Sperm whales are carnivores that primarily hunt squid, but also eat octopuses, fish, and bioluminescent tunicates. The whales have excellent vision and may hunt by watching the water above them for squid silhouettes or by detecting bioluminescence. They can dive for over an hour and at depths up to 6600 feet in search of food, using echolocation to map their surroundings in the dark.

Aside from humans, the only significant sperm whale predator is the orca.

Behavior

Pods of sperm whales sleep at night. The whales position themselves vertically with their heads near the surface.

Mature males form bachelor groups or live solitary lives except for mating. Females group with other females and their young.

Reproduction and Offspring

Females become sexually mature around 9 years of age, while males mature at 18 years. Males fight with other males for mating rights, probably using teeth and ramming competitors. The pair separate after mating, with males providing no care to offspring. After 14 to 16 months gestation, the female gives birth to a single calf. The newborn is about 13 feet long and weighs over one ton. Pod members cooperate to protect calves. Calves typically nurse for 19 to 42 months, sometimes from females besides their mothers. After reaching maturity, females give birth just once every 4 to 20 years. The oldest recorded pregnant female was 41 years old. Sperm whales may live over 70 years.

Conservation Status

The IUCN classifies the sperm whale conservation status as "vulnerable," while the United States Endangered Species Act lists it as "endangered." Sperm whales are listed on Appendix I and Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). Numerous other agreements also protect the whales throughout much of their range. Sperm whales reproduce slowly and are widely distributed, so the total population size and population trend are unknown. Some researchers estimate there may be hundreds of thousands of sperm whales.

Threats

While largely protected worldwide, Japan continues to take some sperm whales. However, the species' greatest threats are ship collisions and entanglement in fishing nets. Sperm whales may also be at risk from chemical pollution, noise pollution, and debris such as plastic.

Sperm Whales and Humans

The sperm whale is featured in Jules Verne's Twenty Thousand Leagues Under the Sea and in Herman Melville's Moby-Dick, which is based on the true story of the sinking of the whaleship Essex in 1820. While sperm whales do not hunt humans, it's theoretically possible a person could be eaten. There is one story of a sailor swallowed by a sperm whale in the early 1900s and surviving the experience.

Sperm whale teeth remain important cultural objects in the Pacific islands. While sperm oil use has fallen out of vogue, ambergris may still be used as a perfume fixative. Today, sperm whales are a source of ecotourism income for whale watching off the coasts of Norway, New Zealand, the Azores, and Dominica.

Sources

• Clarke, M.R. "Function of the Spermaceti Organ of the Sperm Whale." Nature. 228 (5274): 873–874, November, 1970. doi:10.1038/228873a0
• Fristrup, K. M. and G. R. Harbison. "How do sperm whales catch squids?". Marine Mammal Science. 18 (1): 42–54, 2002. doi:10.1111/j.1748-7692.2002.tb01017.x
• Mead, J.G. and R. L. Brownell, Jr. "Order Cetacea". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. 2005. ISBN 978-0-8018-8221-0. 
• Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L. Physeter macrocephalus. The IUCN Red List of Threatened Species 2008: e.T41755A10554884. doi:10.2305/IUCN.UK.2008.RLTS.T41755A10554884.en
• Whitehead, H. and L. Weilgart. "The Sperm Whale." In Mann, J.; Connor, R.; Tyack, P. & Whitehead, H. (eds.). Cetacean Societies. The University of Chicago Press. 2000. ISBN 978-0-226-50341-7.