Pygmy and Dwarf Sperm Whales: Kogia breviceps and K. sima

Abstract

This chapter discusses the characteristics, taxonomy, distribution, abundance, and ecology of pygmy (Kogia breviceps) and dwarf sperm (K. sima) whales. Pygmy sperm whales reach a maximum size of about 3.8 m and a weight of 450 kg. Dwarf sperm whales are smaller at 2.7 m and 272 kg. Adults of both species are dark bluish-gray to blackish-brown dorsally and light below. On the side of the head between the eye and the flipper there is often a crescent-shaped, light-colored mark referred to as a false gill. These whales have the shortest rostrum among living cetaceans, and the skull is markedly asymmetrical. Dwarf and pygmy sperm whales occur worldwide in temperate and tropical waters of the Atlantic, Pacific, and Indian Oceans. Although rarely sighted at sea, these whales commonly strand in some regions, and much of the relatively little that is known of their ecology has been gleaned from such stranded animals. Kogia spp. feed mostly on mid- and deepwater cephalopods but also consume fish and occasionally crustaceans, such as shrimp and crabs. Stomach contents that have been analyzed have contained cephalopod beaks from at least 55 species representing 15 families, although in the northeast Atlantic K. breviceps squids of the genus Histioteuthis predominate. Dwarf and pygmy sperm whales are reported to spend considerable time lying motionless at the surface with the back of the head exposed and the tail hanging down.