Adult males without a harem travel in bachelor groups, obtaining a harem only by fighting and defeating a bull that leads one. Males compete with one another in early spring and summer for control of a group of mature females. A successful male will mate with all the females in his harem. Gestation lasts for about 15 months and the calf, which is 12-16 feet when born, nurses for about two years. After weaning, the female may not become pregnant again for nine months.
Females reproduce only once every four years.
Sperm whales are found in all of the world's oceans, except for the Arctic region. In U.S. waters, they may be found from California and Hawaii north to the Bering Sea, and from Maine to the Gulf of Mexico. They tend to prefer deep waters and generally remain along the edge of continental shelves in water 3,000-6,000 feet deep or further out to sea. When in open waters, this whale may dive for periods of more than one hour at depths of up to 8,000 feet. Hunting was the primary cause of decline in this species.