Chordates • Earth.com

Dwarf sperm whale

(Kogia sima)

galery

Description

The dwarf sperm whale (Kogia sima,formerly Kogia simus) is one of three extant species in the sperm whale family.They are not often sighted at sea,and most extant information comes from the study of stranded carcasses.The dwarf sperm whale is the smallest species commonly known as a whale.It grows up to 2.7 m (8.9 ft) in length and 250 kilograms (550 lb) in weight— making it smaller than the bigger species of dolphin.Specimens often make slow,deliberate movements with little splash or blow and usually lie motionless when at the sea's surface.Consequently,they are usually observed only in very calm seas (Beaufort 0–1).The dwarf sperm whale is similar in appearance and behavior to its relative,the pygmy sperm whale.Identification may be close to impossible at sea;however,the dwarf is slightly smaller and has a larger dorsal fin.The body is mainly bluish gray with a lighter underside with possible yellowish vein-like streaks.A white false gill is behind each eye.The flippers are very short and broad.The top of the snout overhangs the lower jaw,which is small.Dwarves have long,curved,sharp teeth (none to six in the upper jaw and between 14 and 26 in the lower).These teeth led to the species being described as the "rat porpoise" in the Lower Antilles Like other sperm whales,the dwarf has a spermaceti organ in its forehead.Like the pygmy,it is able to expel a dark reddish substance when frightened or attacked—possibly to put off any predators.Dwarf sperm whales are usually solitary,but have occasionally been seen in small pods.The brain of the dwarf sperm whale is roughly 0.5 kg in mass.

Taxonomic tree:

Domain:
Kingdom: Animalia
Phylum:
Class: Mammalia
Order:Cetacea
Family:Kogiidae
Genus:Kogia
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