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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 scale|Beaufort 0–1]]).
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 scale|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, has a larger and more erect [[dorsal fin]]. From field observations, at the surface the back of the whale is more flat from the anterior to the fin<ref>{{Cite journal|url=https://link.springer.com/content/pdf/10.1186/s41200-016-0064-z.pdf|doi=10.1186/s41200-016-0064-z.pdf}}</ref>. That is distinguishable from the [[pygmy sperm whale]], since they have a more rounded back<ref>{{Cite journal|url=https://link.springer.com/content/pdf/10.1186/s41200-016-0064-z.pdf|doi=10.1186/s41200-016-0064-z.pdf}}</ref>. 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. Dwarf sperm whales 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 [[Netherlands Antilles|Lower Antilles]].
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, has a larger and more erect [[dorsal fin]]. From field observations, at the surface the back of the whale is more flat from the anterior to the fin<ref>{{Cite journal|last=Bonato|first=Marco|last2=Webber|first2=Marc A.|last3=Attoumane|first3=Artadji|last4=Giacoma|first4=Cristina|date=2016-07-27|title=First records of dwarf sperm whale (Kogia sima) from the Union of the Comoros|url=http://dx.doi.org/10.1186/s41200-016-0064-z|journal=Marine Biodiversity Records|volume=9|issue=1|doi=10.1186/s41200-016-0064-z|issn=1755-2672}}</ref>. That is distinguishable from the [[pygmy sperm whale]], since they have a more rounded back<ref>{{Cite journal|last=Bonato|first=Marco|last2=Webber|first2=Marc A.|last3=Attoumane|first3=Artadji|last4=Giacoma|first4=Cristina|date=2016-07-27|title=First records of dwarf sperm whale (Kogia sima) from the Union of the Comoros|url=http://dx.doi.org/10.1186/s41200-016-0064-z|journal=Marine Biodiversity Records|volume=9|issue=1|doi=10.1186/s41200-016-0064-z|issn=1755-2672}}</ref>. 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. Dwarf sperm whales 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 [[Netherlands Antilles|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.
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.

Revision as of 03:54, 7 June 2018

Dwarf sperm whale[1]
Temporal range: Pliocene – Recent
↓
[2]
Size compared to an average human
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Kogiidae
Genus: Kogia
Species:
K. sima
Binomial name
Kogia sima
(Owen, 1866)[3]
Dwarf sperm whale range

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.

Taxonomy

Today, the dwarf sperm whale is generally classified as one of two species, along with the pygmy sperm whale, in the family Kogiidae and genus Kogia. The two species were not regarded as separate until 1966. Most taxonomists regard the family Kogiidae as belonging to the superfamily Physeteroidea, though some consider this taxon to be a subfamily (Kogiinae) of the family Physeteridae.

Description

The dwarf sperm whale is the smallest species of cetaceans. 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. Dwarf and pygmy sperm whales possess the shortest rostrum of current day cetaceans with a skull that is greatly asymmetrical[4]. Dwarf sperm whale skull does not have an independent jugal, has prominent supracranial basin and sagittal septum. The left naris is notably larger than the right one.[5]

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, has a larger and more erect dorsal fin. From field observations, at the surface the back of the whale is more flat from the anterior to the fin[6]. That is distinguishable from the pygmy sperm whale, since they have a more rounded back[7]. 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. Dwarf sperm whales 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.[8]

There are no records of sexual dimorphism among dwarf sperm whales[9] .

Diet

Dwarf sperm whales feed mainly on cephalopods, like squid, crustaceans, and fish. [10]

Behavior

Breaching

Dwarf sperm whales and pygmy sperm whales are unique among cetaceans in using a form of "ink" to evade predation in a manner similar to squid. Both species have a sac in the lower portion of their intestinal tract that contains up to 12 l of dark reddish-brown fluid, which can be ejected to confuse or discourage potential predators.[11]

Population and distribution

The dwarf sperm whale lives in tropical and deep waters, but is more coastal than the pygmy sperm.[10] Its favorite habitat appears to be just off the continental shelf. Juvenile whales appear to spend time at the outer section of the shelf and upper portion of the slope; adults exist in deeper waters. [12]In the Atlantic, strandings have been observed in Virginia, United States in the west and Spain and the United Kingdom in the east, and as far south as southern Brazil and the tip of Africa. In 2017 a live specimen was for the first time ever sighted in the North Sea (Belgium, Ostend).[13] In the Indian Ocean, specimens have been found on the south coast of Australia and on many places along the Indian Ocean's northern coast – from South Africa to Indonesia. In the Pacific, the known range includes the Japanese coast, Russia,[14][15] and British Columbia. No global population estimates have been made. One survey estimated a population of about 11,000 in the eastern Pacific.

Lifecycle

The calving season lasts four to five months. Pregnancy lasts for 9 to 11 months. The newborn calf is about 1.0 m long.[16] Males reach puberty at 2.0 m and become sexually mature at 2.1 to 2.2 m.[17]

Human interaction

The dwarf sperm whale was actively hunted by commercial whalers. Occasional harpoon kills are still made by Indonesian and Japanese fishermen. Hunting of these whales had been recorded in Sri Lanka and the Lesser Antilles as well.[18] Since the dwarf is more coastal than the pygmy, it may be more vulnerable to human activities such as fishing and pollution. Insufficient data exist as to whether such activities threaten the species survival. Many deaths happen in accidental fishing gear.[18]

Conservation

The dwarf sperm whale is covered by the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area.[19] The species is further included in the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia (Western African Aquatic Mammals MoU)[20] and the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU).[21]

See also

References

  1. ^ Mead, J. G.; Brownell, R. L. Jr. (2005). "Order Cetacea". In Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 737. ISBN 978-0-8018-8221-0. OCLC 62265494.
  2. ^ Fossilworks works 2013. "fossilworks". fossilworks.{{cite web}}: CS1 maint: numeric names: authors list (link)
  3. ^ a b Taylor, B.L.; Baird, R.; Barlow, J.; Dawson, S.M.; Ford, J.K.B.; Mead, J.G.; Notarbartolo di Sciara, G.; Wade, P.; Pitman, R.L. (2012). "Kogia sima". The IUCN Red List of Threatened Species. 2012. IUCN: e.T11048A17695273. doi:10.2305/IUCN.UK.2012.RLTS.T11048A17695273.en. Retrieved 10 January 2018.
  4. ^ Mcalpine, Donald F. (2009). Encyclopedia of Marine Mammals. Elsevier. pp. 936–938. ISBN 9780123735539.
  5. ^ Willis, P. M., and R. W. Baird. "Status of the dwarf sperm whale, Kogia simus, with special reference to Canada." Oceanographic Literature Review 9.45 (1998): 1640.
  6. ^ Bonato, Marco; Webber, Marc A.; Attoumane, Artadji; Giacoma, Cristina (2016-07-27). "First records of dwarf sperm whale (Kogia sima) from the Union of the Comoros". Marine Biodiversity Records. 9 (1). doi:10.1186/s41200-016-0064-z. ISSN 1755-2672.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  7. ^ Bonato, Marco; Webber, Marc A.; Attoumane, Artadji; Giacoma, Cristina (2016-07-27). "First records of dwarf sperm whale (Kogia sima) from the Union of the Comoros". Marine Biodiversity Records. 9 (1). doi:10.1186/s41200-016-0064-z. ISSN 1755-2672.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  8. ^ Marino, L; Sudheimer, K; Pabst, DA; McLellan, WA; Johnson, JI (2003). "Magnetic resonance images of the brain of a dwarf sperm whale (Kogia simus)". J Anat. 203 (1): 57–76. doi:10.1046/j.1469-7580.2003.00199.x. PMC 1571141. PMID 12892406.
  9. ^ Willis, P. M., and R. W. Baird. "Status of the dwarf sperm whale, Kogia simus, with special reference to Canada." Oceanographic Literature Review 9.45 (1998): 1640.
  10. ^ a b Dunphy-Daly, Meagan M., and Michael R. Heithaus. “Temporal Variation in Dwarf Sperm Whale (Kogia Sima) Habitat Use and Group Size off Great Abaco Island, the Bahamas.” 27 Dec. 2007, doi:10.25148/etd.fi15101248.
  11. ^ "Dwarf sperm whale (Kogia sima)". NOAA Fisheries Office of Protected Resources web site. NOAA. 2014-10-20. Archived from the original on 2013-10-03. Retrieved 2015-01-11.
  12. ^ Willis, P. M., and R. W. Baird. "Status of the dwarf sperm whale, Kogia simus, with special reference to Canada." Oceanographic Literature Review 9.45 (1998): 1640.
  13. ^ "Eerste waarneming van een Kleinste potvis in België". Natuurpunt.be. 31 January 2017.
  14. ^ ХОРОШИЕ НОВОСТИ ПРО ЖИВОТНЫХ. 2017. НА КУНАШИРЕ (КУРИЛЫ) СПАСЛИ ЗАСТРЯВШЕГО НА МЕЛИ РЕДКОГО КАШАЛОТА С ДЕТЕНЫШЕМ. Retrieved on September 26, 2017
  15. ^ 2017. НА КУНАШИРЕ (КУРИЛЫ) СПАСЛИ ЗАСТРЯВШЕГО НА МЕЛИ РЕДКОГО КАШАЛОТА С ДЕТЕНЫШЕМ. Retrieved on September 26, 2017
  16. ^ Petrie, Kristin (2006). Dwarf Sperm Whales. Checkerboard Books. p. 16. ISBN 1596793082.
  17. ^ Nagorsen, David (1985). "Kogia simus" (PDF). Mammalian Species. 239: 1–6.
  18. ^ a b Reeves, Randall R, et al. 2002–2010 Conservation Action Plan for the World’s Cetaceans IUCN/SSC Cetacean Specialist Group: Dolphins, Whales and Porpoises. www.bing.com/cr?IG=69002A33F2BF4041B9FD6CBA0099C9C5&CID=34F64915D91864F230C54512D8E565EA&rd=1&h=Z2NfwgyvGN-id-wPmFrbTxuCJBpbWWs6l-mUn48Topo&v=1&r=http%3a%2f%2fiucn-csg.org%2fwp-content%2fuploads%2f2010%2f03%2fIUCNActionPlan2003-009.pdf&p=DevEx.LB.1,5630.1.
  19. ^ Official website of the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area
  20. ^ Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia. cms.int
  21. ^ Official webpage of the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region. pacificcetaceans.org

Further reading

Wikimedia Commons has media related to Kogia sima.
  • Pygmy and Dwarf Sperm Whales by Donald F. McAlpine in Encyclopedia of Marine Mammals (2002), San Diego: Academic Press, pp. 1007–1009, ISBN 0-12-551340-2
  • 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

Wikispecies has information related to Kogia sima.
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