Sperm Whale

The Sperm Whale is the classic whale of 'Moby Dick' fame, and is the largest of the toothed whales.

Identification

Female Pygmy Sperm Whales are generally only about two-thirds the length of the males and half the weight. Despite this dimorphism, the sexes are very similar in appearance with a shape unlike that of any other whale. Their most prominent feature is the bulbous squared head and huge conical teeth in the lower jaw. The elongated body is a grey colour overall with small stubby flippers and a large powerful tail.

Distribution

The distribution of the Sperm Whale is unique in that, although it is a worldwide species, the sexes appear to operate in separate well-defined parts of the oceans. Both males and females occur in the tropics and temperate areas, but only the males will venture into higher latitudes of the polar areas. Strictly deep-water inhabitants, these whales have the potential for mass strandings if they stray into shallow areas.

Feeding and diet

The Sperm Whale's diet consists almost exclusively of cephalopods (squid and octopus), especially the deep water and ocean bed species. For this prey the whale will sometimes make deep prolonged dives. They have been recorded at depths exceeding a kilometre and can stay submerged for up to 90 minutes.

Life history cycle

Sperm Whales are slow breeding animals, a gestation period of about 15 months, birth of a single young and a long period of maternal care. Females are thought to breed on average, only every four to six years although the period between births can be as long as 15 years. It is these features of the Sperm Whale life history that made the impact of whaling so devastating for the species.

Conservation status

Sperm Whales were commercially hunted up until the 1970s, even in Australia. The reason this species was particularly prized was the super fine body oil and the wax oil or spermaceti contained in the bulbous head. It has a milky appearance, not unlike that of human reproductive sperm hence the common name. Like most species exploited during the whale hunting days, years of official protection has arrested the serious decline in their numbers. They are now the target of the worldwide whale watching industry.

References

• Baker, A. N. 1999. Whales and Dolphins of Australia and New Zealand: an identification guide. Allen & Unwin, St Leonards, Australia.
• Bryden, M., Marsh, H. and Shaughnessy, P. 1998. Dugongs, Whales, Dolphins and Seals. A guide to the sea mammals of Australasia. Allen & Unwin, St Leonards, Australia.
• Menkhorst, P. 2001. A Field Guide to Mammals of Australia. Oxford University Press, Melbourne, Australia.
• Reeves, R. R., Stewart, B. S., Clapham, P. J. and Powell, J. A. 2002. National Audubon Society Guide to Marine Mammals of the World. Chanticleer Press, Inc New York, USA.