The dwarf sperm whale (Kogia sima) is a sperm whale that inhabits temperate and tropical oceans worldwide, in particular continental shelves and slopes. It is a small whale, 2 to 2.7 m (6 ft 7 in to 8 ft 10 in) and 136 to 272 kg (300 to 600 lb), that has a gray coloration, square head, small jaw, and robust body.
In appearance it is quite similar to the pygmy sperm whale, distinguished mainly by the position of the dorsal fin on the body –nearer the middle in the dwarf sperm whale and nearer the tail in the other.
The dwarf sperm whale is a suction feeder that mainly eats squid, and does this in small pods of typically one to four members. It is preyed upon by the killer whale (Orcinus orca) and large sharks such as the great white shark (Carcharodon carcharius). When startled, the whale can eject a cloud of red-brown fluid.
- Food: squid and octopus
- Social Status: Commonly found in groups of 3 – 5
- Breeds annually to 1 calf
- Gestation: 11 months
- Newborn: 1.2 meters long
- IUCN Red List Status: Lower Risk
Population And Habitat
The dwarf sperm whale ranges throughout tropical and temperate oceans of the world and inhabits the continental shelf and slope area. It seems to prefer warmer waters than the pygmy sperm whale.
This whale is one of the most commonly beached deep-diving whales in the world, though rarely seen at sea, and likewise, most information about the whale comes from examining beached individuals. Diving depth may vary from place to place: a study in the Bahamas placed average depth at around 250 m (820 ft), whereas a study in the deeper waters of Hawaii placed it at around 1,500 m (4,900 ft).
In the West Pacific, its recorded range spans from Japan to Tasmania and New Zealand, and in the East Pacific from British Columbia to central Chile. In the Indian Ocean, the whale is reported from Oman, Sri Lanka, India, Thailand, Philippines, Indonesia around Timor, western Australia and South Africa.
In the West Atlantic, it has been recorded from Virginia to southern Brazil, and in the East Atlantic from Italy in the Mediterranean Sea to South Africa.
No global population estimation has been made. Population counts have been taken over certain areas, though given the difficulty to distinguish the dwarf sperm whale from the pygmy sperm whale, the overall estimate represents the total number of both species. In the North Atlantic, they are estimated at around 3,785 individuals; in the East Pacific, around 11,200 individuals.
References:
Caldwell, D. K. and M. C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps; dwarf sperm whale Kogia simus. Pp.235-260 in (S. H. Ridgway and R. Harrison (eds.). Handbook of marine mammals: river dolphins and the large toothed whales. Academic Press, London.
Reeves, R. R. B. S. Stewart, P. J. Clapham and J. A. Powell. 2002. Guide to marine mammals of the world. National Audubon Society, New York.
Scott, M. D. and J. G. Cordaro. 1987. Behavioral observations of the dwarf sperm whale, Kogia simus. Marine Mammal Science 3:353-354.