Sperm Whale: Physeter macrocephalus

Sperm whales are animals of extremes. They have unusually large body sizes, sexual dimorphism, brain sizes, home ranges, dive depths, and dive times; they have an ecological role that may be unrivaled in the ocean; and their vocalizations, social structure, and historical relationship with humans are all remarkable. With the exception of humans and killer whales, few animals on earth are as widely distributed as the sperm whale. They can be seen near the ice-edge in both hemispheres and are also common along the Equator, especially in the Pacific. As with so many aspects of sperm whale biology, the sexes have very different distributions. Concentrations of a few hundred to a few thousand sperm whales can be found in areas a few hundred kilometers across characterized by a relatively high deep water biomass and usually situated within ground. The sperm whale has a most catholic diet consisting of many of the larger organisms that inhabit the deeper regions of the oceans. Females appear to principally eat squid weighing between 0.1 and 10 kg. Males use the same squid taxa as females but tend to eat larger individuals. The sperm whale is the epitome of the ". K-selected" mammal, one presumed to have evolved in an environment of competition for resources with members of its own species. It has a very low birth rate, slow growth, slow maturation, and high survival. The sperm whale has survived the onslaught of the whalers better than most other large whales. There are still a few hundred thousand sperm whales left in the ocean, sperm whale food is of little interest to human fishers, and their deepwater home is farther from most sources of pollution than the preferred habitat of most other marine mammals. However, the effects of whaling seem to be lingering. In the southeast Pacific, where modern whaling on males was particularly severe, large breeding males are still scarce and calving seems depressed below the replacement rate. In other parts of the world, the picture appears brighter. © 2009