View source for Pygmy killer whale

{{Short description|Species of mammal}}
{{Use mdy dates|date=March 2015}}
{{Speciesbox
| name = Pygmy killer whale
| status = LC
| status_system = IUCN3.1
| status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Braulik, G. |date=2018 |title=''Feresa attenuata'' |volume=2018 |page=e.T8551A50354433 |doi=10.2305/IUCN.UK.2018-2.RLTS.T8551A50354433.en |access-date=19 November 2021}}</ref>
| status2 = CITES_A2 
| status2_system = CITES 
| status2_ref = <ref>{{Cite web|title=Appendices {{!}} CITES|url=https://cites.org/eng/app/appendices.php|access-date=2022-01-14|website=cites.org}}</ref>
| image = Pygmy killer whales (Feresa attenuata) off of Guam (anim252384854).jpg
| image_caption = Pod of pygmy killer whales off of Guam
| image2 = Pygmy_killer_whale_size.svg
| image2_caption = Size compared to an average human
| genus = Feresa
| parent_authority = [[John Edward Gray|J. E. Gray]], 1870
| species = attenuata
| authority = ([[John Edward Gray|J. E. Gray]], 1874)
| range_map = cetacea range map Pygmy Killer Whale.PNG
| range_map_alt = A world map shows pygmy killer whales are found throughout all tropical and subtropical portions of the oceans.
| range_map_caption = {{legend2|#0000FF|Range of the pygmy killer whale|outline=gray}}
}}

The '''pygmy killer whale''' ('''''Feresa attenuata''''') is a poorly known and rarely seen [[oceanic dolphin]].<ref name=":4">{{Cite journal|last1=McSweeney|first1=Daniel J.|last2=Baird|first2=Robin W.|last3=Mahaffy|first3=Sabre D.|last4=Webster|first4=Daniel L.|last5=Schorr|first5=Gregory S.|date=2009-07-01|title=Site fidelity and association patterns of a rare species: Pygmy killer whales (Feresa attenuata) in the main Hawaiian Islands|journal=Marine Mammal Science|language=en|volume=25|issue=3|pages=557–572|doi=10.1111/j.1748-7692.2008.00267.x|bibcode=2009MMamS..25..557M |issn=1748-7692}}</ref> It is the [[monotypic taxon|only species]] in the [[genus]] '''''Feresa'''''. It derives its common name from sharing some physical characteristics with the [[orca]], also known as the killer whale. It is the smallest cetacean species that has  the word "whale" in its common name.<ref name=":2">Masa Ushioda, [http://coolwaterphoto.photoshelter.com/gallery/Pygmy-Killer-Whale/G0000DiNxKjwh0og/C00009wjSx5xhBUs “Pygmy Killer Whale”], ”Cool Water Photo”, March 11, 2015</ref> Although the species has been known to be extremely aggressive in captivity, this aggressive behavior has not been observed in the wild.<ref name=":0">{{Cite journal|last=Castro|first=Cristina|title=Encounter with a school of pygmy killer whales (Feresa attenuata) in Ecuador, southeast tropical Pacific|journal=Aquatic Mammals |year=2004 |volume=30 |issue=3 |pages=441–444  |doi=10.1578/AM.30.3.2004.441|bibcode=2004AqMam..30..441C }}</ref>

The species had been described by [[John Edward Gray|John Gray]] in 1874, based on two skulls identified in 1827 and 1874. The next recorded sighting was in 1952 which led to its formal naming by Japanese cetologist Munesato Yamada in 1954.<ref name=":5">{{Cite web|url=http://www.cascadiaresearch.org/Hawaii/pygmykillerwhale.htm|title=Cascadia Research Collective pygmy killer whales in Hawai'i|website=www.cascadiaresearch.org|access-date=2016-03-21|archive-date=October 6, 2016|archive-url=https://web.archive.org/web/20161006061729/http://www.cascadiaresearch.org/Hawaii/pygmykillerwhale.htm|url-status=dead}}</ref>

==Description==
[[File:Feresa attenuata by OpenCage.jpg|thumb|Skeleton of a pygmy killer whale]]

=== Distinguishing features ===

The pygmy killer whale is dark gray to black on the cape and has a sharp change to lighter gray on the sides. The flesh around their lips and on the end of their snout is white while pinkish white skin surrounds the genitals. The average length is just over two meters (6.5&nbsp;ft.). Upon reaching 2 meters in length, males are considered sexually mature. They have approximately 48 teeth, with 22 teeth on the top jaw and 26 on the lower jaw.<ref name=":3">{{Cite journal|title = Biological Data of Pygmy Killer Whale (Feresa attenuata) from a Mass Stranding in New Caledonia (South Pacific) Associated with Hurricane Jim in 2006|journal = Aquatic Mammals|pages = 162–172|volume = 40|issue = 2|doi = 10.1578/am.40.2.2014.162|first = Eric|last = Clua|year = 2014| bibcode=2014AqMam..40..162C }}</ref>

They travel approximately 3&nbsp;km/hour (2 miles/hour)<ref>{{Cite journal|last1=Baird|first1=Robin W.|last2=Schorr|first2=Gregory S.|last3=Webster|first3=Daniel L.|last4=McSweeney|first4=Dan J.|last5=Hanson|first5=M. Bradley|last6=Andrews|first6=Russel D.|date=2011-10-01|title=Movements of two satellite-tagged pygmy killer whales (Feresa attenuata) off the island of Hawai'i|journal=Marine Mammal Science|language=en|volume=27|issue=4|pages=E332–E337|doi=10.1111/j.1748-7692.2010.00458.x|bibcode=2011MMamS..27E.332B |s2cid=14549941 |issn=1748-7692|url=http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1228&context=usdeptcommercepub|url-access=subscription}}</ref> and  are predominately found in deeper waters ranging from 500 m to 2000 m (1600–6500&nbsp;ft.) in depth.<ref name=":4" />

Pygmy killer whales are most commonly confused with [[melon-headed whale]]s and [[false killer whale]]s. For instance, a published paper describing an encounter with a school of pygmy killer whales<ref name=":0" /> was later determined to be either a mixture of pygmy and false killer whales or solely false killer whales.<ref name=":1">{{Cite journal|last=Baird|first=Robin W.|title=Pygmy Killer Whales (''Feresa attenuata'') or False Killer Whales (''Pseudorca crassidens'')? Identification of a Group of Small Cetaceans Seen off Ecuador in 2003|journal=Aquatic Mammals|volume=36|issue=3|pages=326–327|doi=10.1578/am.36.3.2010.326|year=2010|bibcode=2010AqMam..36..326B }}</ref>

The three species can be differentiated by physical differences between them. One defining difference is, although both species have white around the mouth, on pygmy killer whales the white extends back onto the face. Pygmy killer whales also have rounded-tipped dorsal fins, as opposed to pointed tips. When compared to false killer whales, pygmy killer whales have a larger dorsal fin. Finally, pygmy killer whales have a more clearly defined line where the dark dorsal color changes to the lighter lateral color than either of the other two species.<ref name=":1" />

Behavioral differences can also be used to differentiate pygmy killer whales from false killer whales. Pygmy killer whales usually move slowly when at the surface whereas false killer whales are highly energetic. Pygmy killer whales rarely bow ride but it is common in false killer whales.<ref name=":1" />

The small size of this species also causes confusion with other dolphins especially where the frontal head shape of the animals encountered remains unseen. Unlike the melon-headed whale, pygmy killer whales do not normally lift the full face above the water as they surface to breathe so it is not easy to confirm the lack of a bottle. Furthermore, in calmer waters the small bow wave pushed in front of the face looks like a bottle from a distance.<ref name="auto">{{Cite journal|last1=Allport|first1=Gary A.|last2=Curtis|first2=Christopher|last3=Pampulim Simões|first3=Tiago|last4=Rodrigues|first4=Maria J.|date=2017-06-08|title=The first authenticated record of Pygmy Killer Whale (Feresa attenuata Gray 1874) in Mozambique; has it been previously overlooked?|journal=Marine Biodiversity Records|volume=10|issue=1 |pages=17|doi=10.1186/s41200-017-0119-9|issn=1755-2672|doi-access=free|bibcode=2017MBdR...10...17A }}</ref>

=== Early records ===
Prior to the 1950s, the only record of pygmy killer whales was from two skulls identified in 1827 and 1874. In 1952, a specimen was caught and killed in [[Taiji, Wakayama|Taiji]], Japan which is known for its [[Taiji dolphin drive hunt|annual dolphin hunts]]. Six years later, in 1958, an individual was killed off the coast of [[Senegal]]. In 1963, there were two recorded events involving pygmy killer whales. The first was in Japan, where 14 individuals were caught and brought into captivity; all 14 animals were dead within 22 days. The second was off the coast of Hawaii where an individual animal was caught and successfully brought into captivity. In 1967, a single pygmy killer whale off of [[Costa Rica]] died after becoming entangled in a purse seine net. Finally, in 1969, a pygmy killer whale was killed off the coast of St. Vincent and a group of individuals was recorded in the Indian Ocean.<ref name=":5" />

== Echolocation and hearing ==
[[File:Pygmy killer whale necropsy.jpg|thumb|left|Necropsy of two pygmy killer whales by [[NOAA]] scientists.]]
Like other oceanic dolphins, pygmy killer whales use [[Animal echolocation|echolocation]]. The [[Spectral centroid|centroid]] of echolocation frequencies is between 70–85&nbsp;kHz and can range from 32 to 100&nbsp;kHz. This is similar to the range of other odontocetes such as the bottlenose dolphin but is slightly higher than false killer whales. While echolocating, they produce 8-20 clicks per second with a 197-223 decibel sound level at the production source. The linear directionality of sound production in pygmy killer whales is better than in porpoises but lower than is found in bottlenose dolphins; higher directionality results in sounds that are easier to discern from background noise. Based on similarities to the acoustic parameters of other odontocetes, it is presumed that they use a similar mechanism for producing echolocation clicks.<ref>{{Cite journal|title = Source parameter estimates of echolocation clicks from wild pygmy killer whales (Feresa attenuata) (L)|last1 = Madsen|first1 = P. T.|date = 2004|journal = Journal of the Acoustical Society of America|doi = 10.1121/1.1788726 |pmid = 15532623| first2 = I. | last2 = Kerr | first3 = R. | last3 = Payne | volume=116 |issue = 4| pages=1909–1912| bibcode=2004ASAJ..116.1909M }}</ref>

The anatomy for auditory reception is similar to other odontocetes, with a hollow [[mandible]] and a mandibular fat body composed of a low density outer layer and a denser inner core. The inner core comes into direct contact with the tympanoperiotic complex (functionally similar to the [[Tympanic part of the temporal bone|auditory bulla]] in other species - see [[Cetacea#Ears|Cetacea]]). Hearing tests performed on two live individuals brought in for rehabilitation exhibited frequency response range and temporal resolution similar to that found in other echolocating dolphins. During those tests, one individual exhibited low frequency hearing loss that might have been related to treatment with the antibiotic [[amikacin]] although the researchers believed the more likely cause was slight differences in testing setup.<ref>{{Cite journal|last1=Montie|first1=Eric W.|last2=Manire|first2=Charlie A.|last3=Mann|first3=David A.|date=2011-03-15|title=Live CT imaging of sound reception anatomy and hearing measurements in the pygmy killer whale, Feresa attenuata|journal=Journal of Experimental Biology|language=en|volume=214|issue=6|pages=945–955|doi=10.1242/jeb.051599|issn=0022-0949|pmid=21346122|doi-access=free|bibcode=2011JExpB.214..945M }}</ref>

==Population and distribution==
Pygmy killer whales have been observed in groups ranging from 4 to 30 or more individual animals.<ref name=":4" /> The only population estimate is of 38,900 individuals in the eastern tropical [[Pacific Ocean]]; however, this estimate had a large [[coefficient of variation]] meaning the true population size could be much lower or much higher.<ref>{{Cite journal|last1=Wade|first1=P. R.|last2=Gerrodette|first2=T.|date=1993|title=Estimates of cetacean abundance and distribution in the eastern tropical Pacific|journal=Forty-Third Report of the International Whaling Commission |volume=43 |pages=477–493}}</ref>

The species has a wide distribution in tropical and subtropical waters worldwide. They are sighted regularly off Hawaii and Japan.<ref>Author name,[http://eol.org/pages/328531/details “Pygmy Killer Whale”], ”EOL, Encyclopedia of Life”, March 13th, 2015</ref> Appearances in [[bycatch]] suggest a year-round presence in the [[Indian Ocean]] near [[Sri Lanka]] and the [[Lesser Antilles]]. The species has also been found in the south-west Indian Ocean in the [[French Southern and Antarctic Lands]] off [[Europa Island]], [[Mozambique]]<ref name="auto"/> and [[South Africa]]<ref>{{Cite journal|last1=Findlay|first1=K. P.|last2=Best|first2=P. B.|last3=Ross|first3=G. J. B.|last4=Cockcroft|first4=V. G.|date=1992-06-01|title=The distribution of small odontocete cetaceans off the coasts of South Africa and Namibia|journal=South African Journal of Marine Science|volume=12|issue=1|pages=237–270|doi=10.2989/02577619209504706|issn=0257-7615|doi-access=free}}</ref> but not yet recorded off East Africa. In the Atlantic, individuals have been observed as far north as [[South Carolina]] on the west  and [[Senegal]] on the east.<ref>Author name, [http://www.slideshare.net/hellanysales/grzimek-animal-life-encyclopedia-volume-15-mammals-iv “”] {{Webarchive|url=https://web.archive.org/web/20150402133256/http://www.slideshare.net/hellanysales/grzimek-animal-life-encyclopedia-volume-15-mammals-iv |date=April 2, 2015 }}, ”Grzimek Mammals IVAnimal Life Encyclopedia”, March 13th 2015</ref> In May 2023, a sailor named Bryant Irawan, spotted a pod much further north off the coast of Portugal, which was confirmed by scientists at [https://happywhale.com/home happywhale.com].<ref>{{Cite web |title=Check out Bryant Irawan's sighting on Happywhale! |url=https://happywhale.com/user/19463;enc=372967 |access-date=2024-05-14 |website=happywhale.com |language=en}}</ref> They have been observed along the coast of South America and as far north as the Gulf of Mexico where they have been known to breed during the spring season.<ref name=":0" />

A resident population of pygmy killer whales lives in the waters around Hawaii. Most sightings have been around the main island, however there are occasional sightings around several of the other islands. The population has a tightly connected social structure with affiliations between individuals that can last up to 15 years. Despite the existence of this resident population, sightings of pygmy killer whales around Hawaii are still quite rare; they accounted for less than 1.5% of all cetaceans sighted in a study lasting from 1985 to 2007. This population has been observed associating with false killer whales, short-finned pilot whales, and bottlenose dolphins.<ref name=":4" />

Pygmy killer whales are not commonly reported to be found in Thailand. On August 3, 2024, three pygmy killer whales were found stranded in the mangroves of Ao Kung, [[Phuket]]. Local officials were able to safely rescue them and return them to the sea. This is the first time they have been found in Thailand.<ref>หน้า 12 การศึกษา • ชีวิตคุณภาพ • ในประเทศ, ''ช่วยโลมาเกยตื้นอ่าวกุ้งภูเก็ต''. '''[[Matichon|มติชน]]'''วันอาทิตย์ที่ 4 สิงหาคม พุทธศักราช 2567 ปีที่ 47 ฉบับที่ 16947 {{langx|th|ภาษาไทย}}</ref><ref>{{cite news |url=https://www.thephuketnews.com/pygmy-killer-whales-rescued-from-stranding-in-phuket-mangrove-forest-93188.php |title=Pygmy killer whales rescued from stranding in Phuket mangrove forest |author=Eakkapop Thongtub |work=The Phuket News |date=2024-08-03 |access-date=2024-08-04}}</ref>

==Conservation==
Pygmy killer whales have been incidental [[bycatch]] in fishing operations.  They represent as much as 4% of the cetacean bycatch in [[Gillnetting|drift gill nets]] used by commercial fisheries in Sri Lanka.<ref>{{Cite journal|last=Alling|first=Abigail|date=1998|title=A Preliminary Report of the Incidental Trapping of Odontocetes by Sri Lanka's Coastal Driftnet Fishery|journal=Journal of the Bombay Natural History Society |volume=85 |issue=3}}</ref>

Like other cetaceans, they are hosts to parasitic worms such as [[Cestoda|cestodes]] and [[nematode]]s. The cestode species, ''Trigonocotyle sexitesticulae,'' was first discovered in the corpse of a pygmy killer whale.<ref>{{Cite journal|last=Hoberg|first=Eric|date=1989-07-11|title=Trigonocotyle sexitesticulae sp.nov. (Eucestoda: Tetrabothriidae): a parasite of pygmy killer whales (Feresa attenuata)|journal=Canadian Journal of Zoology |volume=68 |issue=9|pages=1835–1838|doi=10.1139/z90-263}}</ref> A pygmy killer whale found stranded on the coast of New Caledonia died from parasitic [[encephalitis]] caused by nematodes. They are also victims of  opportunistic [[Cookiecutter shark|cookie cutter sharks]].<ref name=":3" />

Pygmy killer whales are occasionally involved in [[Cetacean stranding|mass strandings]]. As seen in other cetaceans, these strandings often involve a sick or injured individual; even when pushed back out to the sea by rescuers, the healthy individuals will often strand again and refuse to leave until the death of the individual in declining health.<ref name=":3" />

The pygmy killer whale is classified as [[least concern]] by the [[International Union for Conservation of Nature|IUCN]].<ref name="iucn status 19 November 2021" /> They are covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas ([[ASCOBANS]]) and the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area ([[ACCOBAMS]]). The species is further included in the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia ([http://www.cms.int/species/waam/index.htm Western African Aquatic Mammals MoU]) and the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region ([[Pacific Islands Cetaceans Memorandum of Understanding|Pacific Cetaceans MoU]]).<ref>{{Cite web|url=http://www.ascobans.org/en/species|title=Species|website=ASCOBANS|access-date=2016-03-21}}</ref>

== See also ==
{{Portal|Cetaceans|Mammals|Marine life}}
*[[List of cetaceans]]
*[[Marine biology]]

==References==
{{Reflist}}

==External links==
*[http://www.ascobans.org/ Official website of the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas]
*[http://www.accobams.org/ Official website of the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area]
*[http://www.cms.int/species/waam/index.htm Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia]
*[http://www.pacificcetaceans.org/ Official webpage of the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region]

{{Cetacea|O.}}
{{Odontoceti|D.}}
{{Taxonbar|from=Q244172}}
{{Authority control}}

[[Category:Oceanic dolphins]]
[[Category:Cosmopolitan mammals]]
[[Category:Cetaceans of the Atlantic Ocean]]
[[Category:Cetaceans of the Indian Ocean]]
[[Category:Cetaceans of the Pacific Ocean]]
[[Category:Mammals described in 1874|pygmy killer whale]]
[[Category:Taxa named by John Edward Gray|pygmy killer whale]]