dwarf sperm whale

File:Kogia sima skull.jpg

The first two dwarf sperm whale specimens, a male and a female, were collected in 1853 by naturalist Sir Walter Elliot, who thought it a kind of porpoise due to the short snout. However, when he sent drawings of these whales – including skeletal diagrams – to biologist Richard Owen to describe, Owen, in his 1866 paper, recognized it as a type of sperm whale in the family Physeteridae based on several similar characteristics, such as having functional teeth in only the lower jaw, a lopsided blowhole leaning towards the left side, and a spermaceti organ. He named it Physeter (Euphysetes) simus, the same genus as the sperm whale (Physeter macrocephalus) and the pygmy sperm whale (now Kogia breviceps), with Euphysetes acting as a subgenus.{{cite journal|first=R.|last=Owen|author-link=Richard Owen|year=1866|title=On some Indian Cetacea collected by Walter Elliot, Esq|journal=Transactions of the Zoological Society of London|volume=6|issue=1|pages=17–47|doi=10.1111/j.1096-3642.1866.tb00570.x|url=https://zenodo.org/record/1735626}} The species name simus is Latin for "stump-nosed", a reference to its blunt snout. John Edward Gray, when he created the genus Kogia in 1846, gave no indication to the meaning, but, since the word has a feminine ending, the masculine species name simus had to be changed to sima to fit this when the combination Kogia simus was proposed by various 20th century authors.{{cite book|first=D. W.|last=Rice|year=1998|title=Marine Mammals of the World: Systematics and Distribution|publisher=Society for Marine Mammalogy|pages=84–85|isbn=978-1-891276-03-3|url=http://www.marinemammalscience.org/wp-content/uploads/2014/09/MarineMammalsOfTheWorld.pdf}} In 1900, zoologist Frank Evers Beddard speculated that the word "might be a tribute to a Turk of the past surnamed Cogia Effendi, who observed whales in the Mediterranean".{{cite book | title = A Book of Whales | author = Frank Evers Beddard | year = 1900 | publisher = London, J. Murray; New York, G.P. Putnam's Sons | page = 186 | url = https://archive.org/details/bookofwhales00bedd/page/186/mode/2up }}

In 1871, mammalogist Theodore Gill split Physeteridae into two subfamilies: Physterinae with Physeter, and Kogiinae with Kogia and the now-defunct Euphysetes;{{cite journal|first=T.|last=Gill|author-link=Theodore Gill|year=1871|title=The Sperm Whales, Giant and Pygmy|journal=American Naturalist|volume=4|issue=12|pages=725–743|doi=10.1086/270684|s2cid=84450779|doi-access=free}} this has now been elevated to family, Kogiidae.{{cite WoRMS|title=Kogiidae|id=id=136982|db=Cetacea|access-date=6 August 2018|year=2009}} Gill also proposed the dwarf sperm whale be moved to its own genus, Calignathus. In 1878, naturalist James Hector synonymized the dwarf sperm whale with the pygmy sperm whales as K. breviceps. No distinction was made by most authors until mammalogist Dale Rice in his 1998 review of marine mammal taxonomy citing the works of Dr. Teizo Ogawa from 1936,{{cite journal|first=T.|last=Ogawa|year=1936|title=Studien über die Zahnwale in Japan|language=ja|trans-title=Studies on the Toothed Whales in Japan|journal=Mitteil: Botany & Zoology|volume=4|pages=2017–2023}} researcher Munesato Yamada from 1954,{{cite journal|url=https://www.icrwhale.org/pdf/SC00937-58.pdf|first=M.|last=Yamada|year=1954|title=Some Remarks on the Pygmy Sperm Whale, Kogia|journal=Scientific Reports of the Whales Research Institute|volume=9|pages=37–58}} zoologist Charles Handley from 1966,{{cite book|first=C. O.|last=Handley|author-link=Charles O. Handley|year=1966|title=Whales, Dolphins, and Porpoises|chapter=A Synopsis of the Genus Kogia (pygmy sperm whale)|editor-first=K. S.|editor-last=Norris|publisher=University of California Press|pages=62–69|chapter-url={{google books|plainurl=yes|id=KyxELyTDlsQC|page=62}}}} and mammalogist Graham James Berry Ross from 1979.{{cite book|first=G. J. B.|last=Ross|year=1979|title=Records of Pygmy and Dwarf Sperm Whales, Genus Kogia, from Southern Africa, with Biological Notes and Some Comparisons|publisher=Cape Provincial Museums|series=Annals of the Cape Provincial Museums Natural History|pages=1–60}}

Genetic testing in 2006 suggests that K. sima may actually represent two species, one in the Atlantic and one in the Indo-Pacific region. The Cape of Good Hope around South Africa may mark the barrier between these two populations.{{cite journal|first1=S. J.|last1=Chivers|first2=R. G.|last2=Leduc|first3=K. M.|last3=Robertson|first4=N. B.|last4=Barros|first5=A. E.|last5=Dizon|year=2006|title=Genetic Variation of Kogia spp. with Preliminary Evidence for Two Species of Kogia sima|journal=Marine Mammal Science|volume=21|issue=4|pages=619–634|doi=10.1111/j.1748-7692.2005.tb01255.x|citeseerx=10.1.1.222.2209}}

File:Sperm whales size.svg (blue), the pygmy sperm whale (green), and the dwarf sperm whale (orange)]]

The dwarf sperm whale can range in size from {{convert|2|to|2.7|m|ft|abbr =on}} in length and {{convert|136|to|272|kg|lb|abbr=on}} in weight—less than the {{convert|4.25|m|ft|abbr=on|adj=on|sigfig=2}} and {{convert|417|kg|lb|abbr=on|adj=on|sigfig=2}} pygmy sperm whale. A newborn is generally around {{convert|1|m|abbr=on}} long and {{convert|14|kg|abbr=on}}. Males are thought to reach physical maturity at age 15, and females at age 13. Sexual maturity, which happens after an individual has attained {{convert|2|–|2.2|m|abbr=on}} in length, happens at 2 to 3 years for males and around 5 for females.{{cite thesis | first=Stephanie|last=Plön | date = January 2004 | title=The Status and Natural History of Pygmy (Kogia breviceps) and Dwarf (K. sima) Sperm Whales off Southern Africa|publisher=Rhodes University|url=https://core.ac.uk/download/pdf/145046782.pdf}}{{cite journal|author=Nagorsen, David|year=1985|title=Kogia simus|url=http://www.science.smith.edu/msi/pdf/i0076-3519-239-01-0001.pdf|journal=Mammalian Species|pages=1–6|issue=239|doi=10.2307/3503937|jstor=3503937|access-date=2013-08-01|archive-date=2016-03-04|archive-url=https://web.archive.org/web/20160304053621/http://www.science.smith.edu/msi/pdf/i0076-3519-239-01-0001.pdf|url-status=dead}} Gestation takes place probably over around 9.5 months.

The dwarf sperm whale has a dark-grey or blue-grey coloration with a lighter-grey underside, and a pale, crescent-shaped mark between the eye and the flipper, sometimes called a "fake gill", which is characteristic of the genus. Some individuals have been known to have a second crescent-shaped mark, creating a sort of pale ring encircling a darker spot. It has a high dorsal fin halfway down the length of the body, and two or more throat grooves. The dorsal fin is taller and closer to the head than it is in the pygmy sperm whale, and the back is flatter.

File:Kogia sima.jpg

Kogia is identified as having a square head, a small jaw with the snout jutting outward, and a porpoise-like build with a robust body that rapidly decreases towards the tail. They have the shortest snouts of any modern day whale. Characteristic of sperm whales, the left nostril is markedly larger than the right, and it has a spermaceti organ on its skull.{{cite journal|last1=Willis|first1=P. M.|first2=R. W.|last2=Baird|title=Status of the dwarf sperm whale, Kogia simus, with special reference to Canada|journal=Oceanographic Literature Review|volume=112|issue=1|year=1998|pages=114–125|url=http://whitelab.biology.dal.ca/rwb/kogiastat.pdf}} The brain weighs around {{convert|0.5|kg|lb|abbr=on}}.{{cite journal | pmc = 1571141 | pmid=12892406 | volume=203 | issue=1 | title=Magnetic resonance images of the brain of a dwarf sperm whale (Kogia simus) | journal=Journal of Anatomy | pages=57–76 | last1 = Marino | first1 = L. | last2 = Sudheimer | first2 = K. | last3 = Pabst | first3 = D. A. | last4 = McLellan | first4 = W. A. | last5 = Johnson | first5 = J. I.| year=2003 | doi=10.1046/j.1469-7580.2003.00199.x}} The eyes are adapted for low-light environments. The dwarf sperm whale has 14 to 24 teeth, rarely 26, in the lower jaw that are sharp, slightly curved backwards, and–like other sperm whales–lack enamel. The teeth rarely exceed {{convert|30|mm|in|abbr=on}} in length, smaller than those of the pygmy sperm whale. At most, 6 teeth are in the upper jaws, though in modern sperm whales, upper teeth are defunct.

Unique to Kogia, there is a sac which hangs off from the small intestines near the anus that is filled with a dense, red-brown fluid that looks similar to chocolate syrup. When stressed, this fluid is released. The dwarf sperm whale has between 50 and 57 vertebrae, 7 neck vertebrae, 12 to 14 thoracic vertebrae, and 29 or 35-to-37 lumbar vertebrae. The variation can either be due to loss of bones during preparation of a specimen, or individual variations. It is not known to be sexually dimorphic.{{Cite journal|last1=Bonato|first1=Marco|last2=Webber|first2=Marc A.|last3=Attoumane|first3=Artadji|last4=Giacoma|first4=Cristina|year=2016|title=First records of dwarf sperm whale (Kogia sima) from the Union of the Comoros|journal=Marine Biodiversity Records|volume=9|issue=1|doi=10.1186/s41200-016-0064-z|s2cid=5014340|doi-access=free}}

The dwarf sperm whale ranges throughout tropical and temperate oceans of the world and inhabits the continental shelf and slope area.{{cite book|first1=P|last1=Rudolph|first2=C.|last2=Smeenk|year=2009|chapter=Indo-West Pacific Marine Mammals|title=Encyclopedia of Marine Mammals|editor1-first=W. F.|editor1-last=Perrin|editor2-first=B.|editor2-last=Würsig|editor3-first=J. G. M.|editor3-last=Thewissen|publisher=Academic Press|pages=611|chapter-url={{google books|plainurl=yes|id=2rkHQpToi9sC|page=611}}|isbn=978-0-08-091993-5}} It seems to prefer warmer waters than the pygmy sperm whale. The dwarf sperm 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 {{convert|250|m|abbr=on}}, whereas a study in the deeper waters of Hawaii placed it at around {{convert|1500|m|abbr=on}}.

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;{{cite tech report |veditors=Hayes SA, Josephson E, Maze-Foley K, Rosel PE |date=June 2016 |section=Dwarf Sperm Whale (Kogia sima): Western North Atlantic Stock |section-url=https://www.nefsc.noaa.gov/publications/tm/tm241/67_F2016_dwarfspermwhale.pdf |title=US Atlantic and Gulf of Mexico Marine Mammal Stock Assessments - 2016 |publisher=National Marine Fisheries Service |doi=10.7289/V5/TM-NEFSC-241 |id=NMFS-NE-241}} in the East Pacific, around 11,200 individuals.

File:Histioteuthis reversa (Michael Vecchione, NOAA).JPG (Histioteuthis reversa) is a common prey item.]]

The dwarf sperm whale is an open ocean predator. The stomach contents of stranded dwarf sperm whales comprise mainly squid and, to a lesser degree, deep sea fish (from the mesopelagic and bathypelagic zones) and crustaceans. However, crustaceans make up a sizable part of the diets of Hawaiian dwarf sperm whales, up to 15%. The stomach contents of whales washed up in different regions of the world indicate a preference for cock-eyed squid and glass squid across its range, particularly the elongate jewel squid (Histioteuthis reversa) and Taonius.{{cite journal|first1=M. D.|last1=Staudinger|first2=R. J.|last2=McAlarney|first3=W. A.|last3=McLellan|first4=D. A.|last4=Pabst|year=2013|title=Foraging ecology and niche overlap in pygmy (Kogia breviceps) and dwarf (Kogia sima) sperm whales from waters of the U.S. mid‐Atlantic coast|journal=Marine Mammal Science|volume=30|issue=2|pages=626–655|doi=10.1111/mms.12064|doi-access=free}}

The throat grooves and the developed musculature in the throat in Kogia are probably adaptations for increasing the volume of the mouth for suction feeding, possibly the best-developed among toothed whales. Also, the blunt snout, lack of teeth, and reduced jaw are characteristics seen in other suction feeding toothed whales. The whale uses its sharp teeth to hold onto prey while expelling water from the mouth.{{cite journal|first1=B.|last1=Bloodworth|first2=C. D.|last2=Marshall|year=2005|title=Feeding Kinematics of Kogia and Tursiops (Odontoceti: Cetacea): Characterization of Suction and Ram Feeding|journal=Journal of Experimental Biology|volume=208|issue=Pt 19|pages=3721–3730|doi=10.1242/jeb.01807|pmid=16169949|s2cid=6949085|doi-access=free|hdl=1969.1/180221|hdl-access=free}}

Dwarf sperm whale calves typically start eating solid food once they have reached a size of around {{convert|1.35|m|abbr=on}} though are not fully weaned until they reach around {{convert|1.5|m|abbr=on}}. Toothed whale calves generally start eating solid food at around 6 months, and mothers stop lactating after around 18 to 20 months.

Killer whales (Orcinus orca) and sharks are known to prey on the dwarf sperm whale. Dwarf sperm whale remains have been found in the stomachs of great white sharks (Carcharodon carcharias), and infestations of the cestode Phyllobothrium delphini in beached individuals indicates shark attacks since the cestode matures in sharks.

The dwarf sperm whale also competes with other squid-eating whales, such as beaked whales. It occupies the same ecological niche in the same regions as the pygmy sperm whale, though the latter can forage in deeper waters and has been known to feed on a wider array of species of larger size.

Some beached individuals have had large parasitic infestations which probably lead to their death, particular with nematodes in the stomach and tapeworms in the blubber. In the southeastern United States, stranded dwarf sperm whales were found to have died from heart failure, and heart failure may have led to the stranding itself.{{cite journal|first1=G. D.|last1=Bossart|first2=D. K.|last2=Odell|first3=N. H.|last3=Altman|year=1985|title=Cardiomyopathy in Stranded Pygmy and Dwarf Sperm Whales|journal=Journal of the American Veterinary Medical Association|volume=187|issue=11|pages=1137–1140|pmid=4077624}}

Although Dwarf sperm whales swim in the deep waters far from the shore, they still possess some important escaping mechanisms. “If a Dwarf sperm whale is frightened, it may secrete a red liquid. This causes a cloud to form that stops or distracts predators. This allows the whale to dive deep into the ocean and escape” (Petrie, 2005). Even though Dwarf sperm whales were believed to be in the deep ocean, they have recently been surfacing at the top, putting them in danger by humans. In Japan’s southern coast and Indonesia a small amount of Dwarf sperm whales are being accidentally captured in fishing nets and sold at fish markets. “They are also being put at health risk due to human pollution, ingestion of marine debris, and potential ship strikes” (Reed et al., 2015).

{{Multiple image

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Kogia is thought to be slow-moving, rarely displaying rapid surfacing behavior, tending to float at the surface with only the nape and dorsal fin exposed. From the surface, they sink vertically, instead of lifting their tails out of the water to dive, which would create a splash.

The dwarf sperm whale congregates into small pods of one to four individuals, though on occasion up to ten, likely due to limited food resources. Small group size and deep foraging grounds in the summer could also be anti-predator behaviors. However, this is less likely as dolphins congregate in large pods with hundreds of members to prevent predation. The whale probably follows seasonal squid migrations from offshore in the summer to nearshore in the winter. It is possible it prefers a slope habitat as it allows the whale to herd squid against the wall, or it causes upwelling which the whale can ride on in order to save energy while hunting.{{cite journal|last1=Dunphy-Daly|first1=M. M.|first2=M. R.|last2=Heithaus|title=Temporal Variation in Dwarf Sperm Whale (Kogia sima) Habitat Use and Group Size off Great Abaco Island, the Bahamas|year=2007|doi=10.25148/etd.fi15101248|doi-access=free}}{{Cite journal |last1=Bermúdez Villapol |first1=A Luis |last2=Sayegh |first2=Alejandro |last3=León |first3=Tatiana |date=2008 |title=Notes on the confirmation of the Dwarf sperm whale Kogia sima Owen, 1866 (Cetacea: Kogiidae) on Venezuelan coasts |url=http://www.bioline.org.br/pdf?cg08020 |journal=Revista Científica UDO Agrícola |volume=8 |issue=1 |pages=154–162 |via=Bioline}} Younger animals may congregate in shallower areas and adults in deeper areas; the slope around South Africa may be a nursery grounds.

Kogia, unlike other whales, can eject a red-brown fluid when startled, likely to distract predators, similar to squid. This cloud can cover {{convert|100|sqm|abbr=on}} in the water.

This species does not whistle, and instead produces narrowband high-frequency clicks. These clicks are more similar to those produced by some dolphin and porpoise species–such as the hourglass dolphin (Sagmatias cruciger), Hector's dolphin (Cephalorhynchus hectori), the Chilean dolphin (Cephalorhynchus eutropia), Commerson's dolphin (Cephalorhynchus commersonii), the harbour porpoise (Phocoena phocoena), and Dall's porpoise (Phocoenoides dalli)–than to those of other deep-diving whales, such as beaked whales and the sperm whale. The peak frequencies of Kogia are generally less than 130 kHz.{{cite journal|first1=K.|last1=Merkens|first2=D.|last2=Mann|first3=V. M.|last3=Janik|first4=D.|last4=Clarige|first5=M.|last5=Hill|first6=E.|last6=Oleson|year=2018|title=Clicks of Dwarf Sperm Whales (Kogia sima)|journal=Marine Mammal Science|volume=34|issue=4|pages=963–978|doi=10.1111/mms.12488|hdl=10023/17127|doi-access=free|hdl-access=free}}

There is some hunting of the dwarf sperm whale in Indonesia, Japan, Sri Lanka, and the Lesser Antilles as food or bait, though there are no major operations. A bigger threat is likely ingestion of marine debris and entanglement in fishing gear, though it has not been determined how serious a threat these pose.{{cite book|last1=Reeves|first1=R. R.|first2=B. D.|last2=Smith|first3=G. N.|last3=di Sciara|year=2003|url=http://iucn-csg.org/wp-content/uploads/2010/03/IUCNActionPlan2003-009.pdf|title=2002–2010 Conservation Action Plan for the World's Cetaceans|publisher=IUCN/SSC Cetacean Specialist Group: Dolphins, Whales and Porpoises|isbn=978-2-8317-0656-6}} The International Union for Conservation of Nature (IUCN) currently lists the dwarf sperm whale's conservation status as data deficient, though it could possibly be of least concern.

The dwarf sperm whale is covered by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area.{{cite web|url=http://www.accobams.org/new_accobams/wp-content/uploads/2017/01/ACCOBAMS_Text_Agreement_English.pdf|title=Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area|year=1996|access-date=2018-08-13|archive-date=2017-09-18|archive-url=https://web.archive.org/web/20170918215135/http://www.accobams.org/new_accobams/wp-content/uploads/2017/01/ACCOBAMS_Text_Agreement_English.pdf|url-status=dead}} 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),{{cite web|url=https://www.cms.int/en/species/kogia-sima|title=Kogia sima|publisher=Convention on the Conservation of Migratory Species of Wild Animals}} and the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU).{{cite web|url=http://www.pacificcetaceans.org/diversity.php|archive-url=https://web.archive.org/web/20120331062525/http://www.pacificcetaceans.org/diversity.php|url-status=dead|archive-date=2012-03-31|title=Diversity Database|publisher=Pacific Cetaceans Memorandum of Understanding}}

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{{Reflist}}

Petrie, K. (2005). Dwarf Sperm Whales. ABDO Publishing Company.

Piboon, P., Kriengsakpichit, N., Poommouang, A., Buddhachat, K., Brown, J. L., Kampuansai, J., Chomdej, S., Kaewmong, P., Kittiwattanawong, K., & Nganvongpanit, K. (2022). Relationship of stranded cetaceans in Thai territorial waters to global populations: Mitochondrial DNA diversity of Cuvier’s beaked whale, Indo Pacific finless porpoise, pygmy sperm whale, and dwarf sperm whale. Science Progress, 105(2), 003685042211037. [https://doi.org/10.1177/00368504221103776 Relationship of stranded cetaceans in Thai territorial waters to global populations: Mitochondrial DNA diversity of Cuvier's beaked whale, Indo Pacific finless porpoise, pygmy sperm whale, and dwarf sperm whale]

Reed, L. A., McFee, W. E., Pennington, P. L., Wirth, E. F., & Fulton, M. H. (2015). A survey of trace element distribution in tissues of the dwarf sperm whale ( Kogia sima ) stranded along the South Carolina coast from 1990–2011. Marine Pollution Bulletin, 100(1), 501–506. [https://doi.org/10.1016/j.marpolbul.2015.09.005 A survey of trace element distribution in tissues of the dwarf sperm whale (Kogia sima) stranded along the South Carolina coast from 1990–2011]

• Whales Dolphins and Porpoises, Mark Carwardine, Dorling Kindersley Handbooks, {{ISBN|978-0-7513-2781-6}}
• National Audubon Society Guide to Marine Mammals of the World, Reeves, Stewart, Clapham and Powell, {{ISBN|978-0-375-41141-0}}

{{Commons category|Kogia sima}}

{{Wikispecies|Kogia sima}}

• [https://uk.whales.org/ Whale & Dolphin Conservation Society (WDCS)]

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Category:Sperm whales

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Category:Mammals described in 1866

Category:Taxa named by Richard Owen