Giant beaked whale

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Giant beaked whale
Arnoux's beaked whale size.svg
Size of Arnoux's beaked whale compared to an average human
Baird's beaked whale size.svg
Size of Baird's beaked whale compared to an average human
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Class: Mammalia
Order: Artiodactyla
Family: Ziphiidae
Subfamily: Berardiinae
Genus: Berardius
Duvernoy, 1851
Binomial name
Berardius arnuxii
Duvernoy, 1851
Cetacea range map Arnoux 27s Beaked Whale.png
Arnoux's Beaked Whale range
Berardius bairdii
Stejneger, 1883
Cetacea range map Baird 27s Beaked Whale.png
Baird's Beaked Whale range

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Giant beaked whales are two species of beaked whales in the genus Berardius: Arnoux's beaked whale (Berardius arnuxii) in cold Southern Hemisphere waters, and Baird's beaked whale (Berardius bairdii) in the cold temperate waters of the North Pacific. They are the largest of the beaked whales, growing up to 10–12 m in length. They are sometimes referred to as "four-toothed whales" or "giant beaked whales", but are most commonly known by their genus name, Berardius. Arnoux's and Baird's beaked whales are so similar that researchers have debated whether or not they are simply two populations of the same species. However, genetic evidence and their wide geographical separation has led them to be classified as separate.

Physical description

Illustration of Baird's beaked whale.

The two species have very similar features and would be indistinguishable at sea if they did not exist in disjoint locations. Arnoux's is generally smaller. Estimated lengths of live Arnoux's at sea have been up to 12 m (39 ft), but all dead specimens have been considerably smaller of around 9.3 m (31 ft) to 9.75 m (32.0 ft).[1] The Baird's, on the other hand, have been confirmed to grow to 12–13 m (39–43 ft). The weight is up to 14,000 kg (31,000 lb).

Both whales have a very long prominent beak, even by beaked whale standards. The lower jaw is longer than the upper and the front teeth are visible even when the mouth is fully closed. The melon is particularly bulbous. The body shape is slender—the girth is only 50% of length. The body is uniformly coloured and a particular individual's colour may be anything from light grey through to black. The flippers are small, rounded and set towards the front of the body. The dorsal fin similarly is small and rounded and set about three-quarters of the way along the back. Adult males and females of both species pick up numerous white linear scars all over the body as they age and may be a rough indicator of age. There is little sexual dimorphism in either species.

Population and distribution

The total population is not known for either species. Estimates for Baird's are of the order of 30,000 individuals.

The two species' have an allopatric (non-overlapping) antitropical distribution. Arnoux's beaked whales inhabit great tracts of the Southern Ocean. Beachings in New Zealand and Argentina indicate the whale may be relatively common in the areas south of those countries south to Antarctica, and sporadic sightings have been recorded in polar waters such as McMurdo Sound.[2] It has also been spotted close to South Georgia and South Africa, indicating a likely circumpolar distribution. The northernmost stranding was at 34 degrees south, indicating the whales inhabit cool and temperate, as well as polar, waters.

Baird's beaked whale is found in the North Pacific Ocean, the Sea of Japan and the southern part of the Sea of Okhotsk. They appear to prefer seas over steep cliffs at the edge of the continental shelf, but are known to migrate to oceanic islands and to near shore waters where deep cliffs locate next to landmasses such as at Rishiri Island and in Tsugaru Strait, Shiretoko Peninsula, Tokyo Bay, and Toyama Bay. Specimens have been recorded as far north as the Bering Sea and as far south as the Baja California Peninsula on the east side and the southern islands (Izu and Bonin Islands) of Japan on the west although it is unclear whether records at these islands are of Berardius bairdii. Southern limits of historical occurrences in east Asian were unclear, while there had been a stranding in East China Sea at Zhoushan Islands.[3] Whales off the east coast of North America seems to approach coasts less frequently than in the western North Pacific, but they may travel further south than in Japan. Historical distributions of southward migrations or vagrants in Asian waters are unknown as the whales wintering from Boso Peninsula and in Tokyo Bay to Sagami Bay and around Izu Oshima have been severely depleted or nearly wiped out by modern whaling (recently whalers shifted their major hunting grounds from Boso Peninsula to further north due to the very small numbers of whales still migrating to the former habitats).

Historic and current statuses of northern species in northwestern coastal Pacific out of Japanese EEZ are rather vague especially within North and South Koreas and China. In Chinese waters, the species has been recognized not to occur, at least not constantly, and the locational origin of the skeletal specimen at the Zhejiang Museum of natural History is unreliable although it was collected in the nation.[4] However, archeological records suggest that there could have been historical migrant groups of Baird's Beaked Whales once regularly reached into Yellow and Bohai Seas especially around the island of Lingshan off Jiaozhou Bay and off Dalian.[5] until being wiped out by Japanese whalers. Some could have reached into southern regions at least at Zhoushan archipelago.[3] See also Wildlife of China for natural histories of large cetaceans in this region.

Behavior

Arnoux's beaked whale

Little is known about the behavior of Arnoux's beaked whale, but is expected to be similar to that of Baird's. The whales normally move in close-knit groups of about three to ten, with groups of 50 observed in exceptional circumstances. Considering the extent of whaling of the Baird's species, the pod structure is not well known. Two-thirds of all whales caught have been male, despite the fact females are somewhat larger than males and would be the preferred targets for whalers. Observations of possibly the same group of Arnoux's Beaked Whales cavorted in Doubtful Sound, New Zealand in the same seasons in 2009[6] and in 2010[7] indicate that this species may possess a form of bond to locations similar to those of other species such as Right Whales. Another 4 or 5 sightings have been recorded in the Doubtful Sound between 2007 and in 2011.[8][9]

Species

Berardius is currently classified as containing two species: Arnoux's beaked whale (Berardius arnuxii) in the Southern Hemisphere waters, and Baird's beaked whale (Berardius bairdii) in the North Pacific.[10] Arnoux's beaked whale was described by Georges Louis Duvernoy in 1851. The genus name honors admiral Auguste Bérard (1796-1852), who was captain of the French corvette Le Rhin (1842-1846), which brought back the type specimen to France where Duvernoy analyzed it; the species name honors Maurice Arnoux, the ship's surgeon who found the skull of the type specimen on a beach near Akaroa, New Zealand.[11] Baird's beaked whale was first described by Leonhard Hess Stejneger in 1883 from a four-toothed skull he had found on Bering Island the previous year. The species is named for Spencer Fullerton Baird, a past Secretary of the Smithsonian Institution.[12]

Researchers have debated over whether the northern and southern populations represent distinct species or whether they are simply geographic variants.[13] Several morphological characters have been suggested to distinguish them, but the validity of each has been disputed;[14][15][16] currently, it seems that there are no significant skeletal or external differences between the two forms, except for the smaller size of the southern specimens known to date.[17][18] The morphological similarity gave rise to the hypothesis that the populations were sympatric as recently as the last Pleistocene Ice Age, approximately 15,000 years ago,[10][19] but subsequent genetic analyses suggest otherwise.[20] Phylogenetic analyses of the mitochondrial DNA control region (D-loop) revealed that Baird's and Arnoux's beaked whales were reciprocally monophyletic — lineages from each of the species grouped together to the exclusion of lineages from the other species. Diagnostic DNA substitutions were also found. These results are consistent with the current classification of Baird's and Arnoux's beaked whales as distinct species. Further, the degree of differentiation between the northern and southern forms of Berardius suggest that the species may already have been separated for several million years.[20]

Possible new species

Sightings during whale watching tours and studies of stranded individuals suggest the possibility of another form of Berardius in the Sea of Okhotsk inclusive of the coast of northern Hokkaido especially around Shiretoko Peninsula and off Abashiri.[21][22][23] These whales are generally much smaller than known species (6-7m), darker in color, and inhabit shallow waters closer to coastal areas, enough to be trapped within fixed nets for salmons.[24] Local whalers had called them "Kurotsuchi" (= Black Baird's) or "Karasu" (= Ravens). According to genetic studies, these whales are distinct from any of the known Berardius beaked whales in the Pacific. "Bottlenose whales in the Sea of Okhotsk" had been reported since the time of the Soviet Union's whaling,[25] and an unknown type of beaked whale resembling Baird's beaked whales having 4 tusks on upper and lower jaws has also been recorded by traditional whalers in Japan.[26] It is unknown whether these records correspond with this new form.

An unknown type of large beaked whale of similar size to fully grown Berardius bairdii have been reported to live in the Sea of Okhotsk. These whales have heads somewhat resembling Longman's Beaked Whales, or of a carcass of unspecified megafauna stranded on Moore's Beach on Monterey Bay in 1925,[27] so called "California's Nessie" (although the skull[28] and jawbones[29] specimen clearly showing features of Ziphiidae sp.). There have been claims that records of strandings of these whales exist along the areas within and adjacent to Tatar Strait in 2010s.[30]

Conservation

Arnoux's beaked whale has rarely been exploited, and although no abundance estimates are available, the population is not believed to be endangered. Arnoux's beaked whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).[31]

In the 20th century, Baird's beaked whales were hunted primarily by Japan and to a lesser extent by the USSR, Canada and the United States. The USSR reported killing 176 before hunting ended in 1974. Canadian and American whalers killed 60 before halting in 1966. Japan killed around 4000 individuals before the 1986 moratorium on whaling. About 300 were killed in the most prolific year, 1952. Baird's beaked whales are not protected under the International Whaling Commission's moratorium on commercial whaling, as Japan argues they are a 'small cetacean' species, despite being larger than minke whales, which are protected. Each year, 62 Baird's beaked whales are hunted commercially in Japan, with the meat sold for human consumption. A landing and processing of a Baird's beaked whale was filmed[32] by the Environmental Investigation Agency on 7 August 2009. Meat and blubber food products of the whales have been found to contain high levels of mercury and other pollutants, such as PCBs. The conservation status of Baird's beaked whales is not known globally;[33] the Mammalogical Society of Japan lists them as rare in Japanese coastal waters.

The Baird's beaked whale is listed on Appendix II [34] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II [34] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements. It is considered Data Deficient by the IUCN.

Common names

  • B. arnuxii is known as Arnoux's beaked whale, southern four-toothed whale, southern beaked whale, New Zealand beaked whale, southern giant bottlenose whale, and southern porpoise whale.
  • B. bairdii is known as Baird's beaked whale, northern giant bottlenose whale, North Pacific bottlenose whale, giant four-toothed whale, northern four-toothed whale, and North Pacific four-toothed whale.

Specimens

  • MNZ MM002654 B. arnuxii Arnoux's beaked whale, collected Riverton, near Invercargill, New Zealand, 27 January 2006

See also

References

  1. ↑ http://us.whales.org/species-guide/arnouxs-beaked-whale
  2. ↑ http://eveningreport.nz/2016/03/10/mystery-whales-put-on-show-at-scott-base/
  3. ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Matthews Z., Whales at Doubtful Sound, Fiordland Kindergarten-Blog of Fiordland Nature Discovery, 28 April 2009, http://fiordlandkindy.blogspot.jp/2009/04/whales-at-doubtful-sound.html., Retrieved 4 May 2014
  7. ↑ Department of Conservation, April 2011, Fiordland Coastal Newsletter - Conservation for prosperity – Tiakina te taiao, kia puawai, http://www.fiordlandhelicopters.co.nz/wp-content/uploads/2011/05/Fiordland-Coastal-Newsletter-April-2011.pdf., Retrieved 4 May 2014
  8. ↑ Rockwell D.H., 2009, When in Rome, Do as the Whales Do!
  9. ↑ Hudgins J., Bachara W., 2014. Multiple Opportunistic Observations of Arnoux’s beaked whales in Doubtful Sound (Patea). SC/65b/SM19. Retrieved 14 May 2014
  10. ↑ 10.0 10.1 Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Beolens, Bo, Michael Watkins, and Michael Grayson. 2009. The eponym dictionary of mammals. Baltimore: Johns Hopkins University Press, p. 38, 54.
  12. ↑ Sharks and Whales (Carwardine et al. 2002), p. 356.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  19. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  20. ↑ 20.0 20.1 Lua error in package.lua at line 80: module 'strict' not found.
  21. ↑ Kitano S., 2013. DNAで未知の鯨種に挑む－日本近海のツチクジラについて－. Cetoken Newsletter No.32. Retrieved on January 26, 2014
  22. ↑ Shiretoko Nature Cruise. 2013. 羅臼の海大集合！ 知床ネイチャークルーズ　ニュース Retrieved 26 January 2014
  23. ↑ Uni Y., Koyama K., Nakagun S., Maeda M., 2014. Sighting Records of Cetaceans and Sea Birds in the Southern Okhotsk Sea, off Abashiri, Hokkaido. Bulletin of the Shiretoko Museum 36: pp.29–40. Retrieved on 30 May 2014
  24. ↑ Uni Y., Photos from Abashiri Nature Cruise
  25. ↑ Uni Y.,2006 Whales, Dolphins and Porpoises off Shiretoko. Bulletin of the Shiretoko Museum 27: pp.37-46. Retrieved on 26 January 2014
  26. ↑ T. Kasuya, 2011. イルカ―小型鯨類の保全生物学. University of Tokyo Press. Retrieved on 26 January 2014
  27. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  28. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  29. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  30. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  31. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  32. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  33. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  34. ↑ 34.0 34.1 "Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5 March 2009.

External links

zh:阿氏貝喙鯨

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