Sperm Whale: The Largest Toothed Creature on Earth

Abstract

Among large variations in size, habitat use, trophic niche, and social systems of toothed whales, one species—the sperm whale—stands out as an animal of extremes. The world’s largest biological sonar operated by the largest brain on Earth shapes much of sperm whales’ lives as efficient predators, exploiting massive biological resources at great depths. They are nomads with home ranges spanning thousands of kilometers horizontally and more than a kilometer vertically. These three-dimensional movements and extremely low reproductive rates place a premium on cooperative calf care, making it central to the tight matrilineal social units of female sperm whales in tropical and subtropical waters. The social units themselves are elements of sympatric cultural clans with distinctive behaviors and vocal dialects. Males leave their maternal units in their teens, gradually moving to higher latitudes and becoming less social until, when very much larger than the females, they make periodic forays to warmer waters for mating. New technology is beginning to give us insight into the behaviors of this extraordinary animal, but its long life span means that long-term studies using simple methods are still immensely valuable.