Pygmy sperm whale

Taxobox
name = Pygmy sperm whaleMSW3 Cetacea|id=14300128]
status = DD
status_system = iucn3.1
status_ref =IUCN2008|assessors=Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L.|year=2008|id=11047|title=Kogia breviceps|downloaded=7 October 2008]

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image2_caption = Size comparison against an average human
regnum = Animalia
phylum = Chordata
classis = Mammalia
subclassis = Eutheria
ordo = Cetacea
subordo = Odontoceti
familia = Kogiidae
genus = "Kogia"
species = "K. breviceps"
binomial = "Kogia breviceps"
binomial_authority = Blainville, 1838
range_

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range_map_caption = Pygmy sperm whale range

The pygmy sperm whale ("Kogia breviceps") is one of three species of toothed whale in the sperm whale family. They are not often sighted at sea, and most of our understanding of the creatures comes from the study of washed-up specimens.

Taxonomy

There has been debate and differing opinion as to the correct classification of the Pygmy and dwarf sperm whales (see sperm whale family for details). The two were widely considered to be the same species, until 1966, when a scientist at the Smithsonian Institution definitively diagnosed them as separate species.Fact|date=April 2007 The pygmy sperm whale was first named by Blainville in 1838.Fact|date=April 2007

Physical description

Like its giant cousin, the sperm whale, the pygmy sperm whale has a spermaceti organ in its forehead (see Sperm Whale for a discussion of its purpose). It also has a sac in its intestines that contains a dark red fluid. The whale will expel this fluid when frightened. Its purpose is believed to be to confuse and disorient predators.

The Pygmy Sperm is amongst the smallest of all whales and is not much larger than many dolphins. They are about 1.2 m at birth, growing to about 3.5 m at maturity. Adults weigh about 400 kg. The underside is a creamy, occasionally pinkish, colour and the back and sides are a bluish grey; there is, however, considerable intermixing between the two colours. The head is large in comparison to body size, given an almost swollen appearance when viewed from the side. The lower jaw is very small and slung low. The blowhole is displaced slightly to the left when viewed from above facing forward. The dorsal fin is very small and hooked; its size is considerably smaller than the Dwarf Sperm Whale's and may be used for diagnostic purposes. The Pygmy Sperm has between 20 and 32 teeth, all of which are set into the lower jaw. There is a false gill behind each eye.

This whale makes very inconspicuous movements. It rises to the surface slowly, with little splash or blow, and will remain there motionless for some time. In Japan the whale was historically known as the "floating whale" because of this. Its dive is equally lacking in grand flourish - it simply drops out of view. The species has a tendency to back away from rather than approach boats. Breaching has been observed, but is not common.

Pygmy Sperms are usually solitary creatures but have been seen in groups of up to six. Primary food sources are squid and crabs.

Population and distribution

Pygmy sperm whales are found in the temperate waters of the Atlantic, Pacific and Indian Oceans. However, they are rarely sighted at sea, so most data comes from stranded animals - making a precise range and migration map difficult. They are believed to prefer off-shore waters. Their status is usually described as rare, but occasional patches of higher density of strandings suggest it may be rather more common than previously supposed. The total population is unknown.

Human interaction

Pygmy sperm whales have never been hunted on a wide scale. Land-based whalers have hunted them from Indonesia, Japan and the Lesser Antilles. Individuals have also been recorded killed in drift nets. Some stranded animals have been found with plastic bags in their stomachs - which may be a cause for concern. It is not known whether these activities are causing long-term damage to the survival of the species.

References

* "Pygmy and Dwarf Sperm Whales" by Donald F. McAlpine in "Encyclopedia of Marine Mammals" pp. 1007-1009 ISBN 978-0-12-551340-1
* "Whales Dolphins and Porpoises", Mark Carwardine, Dorling Kindersley Handbooks, ISBN 0-7513-2781-6
* "National Audubon Society Guide to Marine Mammals of the World", Reeves, Stewart, Clapham and Powell, ISBN 0-375-41141-0

External links

* [http://www.wdcs.org Whale & Dolphin Conservation Society (WDCS)]
* [http://www.chena.org/max/pygmysperm/index.htm Max Newman's Pygmy Sperm Whale Research Paper]
* [http://news.bbc.co.uk/2/hi/asia-pacific/7291501.stm dolphin rescues Pygmy Sperm whales]