Spade-toothed whale

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Spade-toothed whale
Mesoplodon traversii.jpg
Skeleton of Mesoplodon traversii
CITES Appendix II (CITES) [2]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Ziphiidae
Genus: Mesoplodon
Species:
M. traversii
Binomial name
Mesoplodon traversii
(Gray, 1874)
Mesoplodon traversii distribution.png
Locations and dates of specimens
Synonyms

Dolichodon traversiiGray, 1874
Mesoplodon bahamondiReyes, van Waerebeek, Cárdenas and Yáñez, 1995

Contents

The spade-toothed whale (Mesoplodon traversii) is a very little-known species, the rarest species of beaked whale.

Discovery

Skull of M. traversii from New Zealand (referred to M. layardii in the original description). Mesoplodon traversii TPRSNZ1872-5.2.6.1.19-a14-700w.jpg
Skull of M. traversii from New Zealand (referred to M. layardii in the original description).

It was first named from a partial jaw found on Pitt Island, New Zealand, in 1872; reported and illustrated in 1873 by James Hector (referring it to M. layardii), and described as a new species the next year by John Edward Gray, who named it in honor of Henry Hammersley Travers, the collector. [3] [4] This was eventually lumped with the strap-toothed whale, starting as early as an 1878 article by Hector, who never considered the specimen to be specifically distinct. [5] A calvaria found in the 1950s at White Island, also New Zealand, initially remained undescribed, but was later believed to be from a ginkgo-toothed beaked whale. [6]

In 1993, a damaged calvaria was found washed up on Robinson Crusoe Island, Chile, and was described as a new species, Mesoplodon bahamondi or Bahamonde's beaked whale. [7]

In December 2010, two specimens, a cow and calf, were found stranded on Opape Beach, Bay of Plenty, New Zealand. They were originally thought to be Gray's beaked whale, but later genetic analysis revealed that they represented the first complete specimens of the spade-toothed whale. [8] Following this find, a report describing the spade-toothed whale and an analysis of their DNA later appeared in the 6 November 2012 issue of the journal Current Biology . [9] [10]

The results of DNA sequence and morphological comparisons have shown all three finds came from the same species, which is therefore properly known as M. traversii. [11] The external appearance was only described in 2012, and it is likely to be the most poorly known large mammalian species of modern times.

Because of where these specimens were initially located at, it is assumed that the remaining population of M. traversii lives solely in the South Pacific. [12]

Physical description

Size comparison to an average human. Mesoplodon traversii.svg
Size comparison to an average human.

Until 2012, nothing was known about this species other than cranial and dental anatomy. Some differences exist between it and other mesoplodonts, such as the relatively large width of the rostrum. Its appearance might be most similar to an oversized ginkgo-toothed beaked whale in overall shape, as their skulls are quite alike except in size. The distinguishing characters are the very large teeth, 23 cm (9 in), close in size to those of the strap-toothed whale. The teeth are much wider than those of the strap-toothed, and a peculiar denticle on the tip of the teeth present on both species is much more pronounced in the spade-toothed whale. It is believed that only the males obtain the jutted denticle and that it smoothens over time due to aggressive behavior with other males. [13] The common name was chosen because the part of the tooth that protrudes from the gums (unlike the strap-like teeth of strap-toothed whales) has a shape similar to the tip of a flensing spade as used by 19th-century whalers.

Despite the rather similar dentition, the spade-toothed whale and strap-toothed whale seem to be only distantly related. The present species' relationships are not known with certainty, though, because this species is very distinct morphologically, and the DNA sequence information is contradictory and is currently not good enough to support a robust phylogenetic hypothesis. [11] [14] Judging from the size of the skull, the species was thought to be between 5.0 and 5.5 m (16.4 and 18.0 ft) in length, perhaps a bit larger. The only known complete specimens are a 5.3-m (17.4-ft) adult female and her 3.5-m (11.5-ft) male calf. The cow was spindle-shaped, with a triangular dorsal fin with a concave trailing edge set about two-thirds the way back. It was dark gray or black dorsally and white ventrally, with a light thoracic patch created by a diagonal band that extends from behind the eye downwards and back to the dorsal fin. It also has a dark eye patch, rostrum, and flippers. [8]

Ecology and status

This species has never been seen alive, so nothing is known of its behavior. It is presumably similar to other medium-sized Mesoplodon , which are typically deep-water species living alone or in small groups and feeding on cephalopods and small fish. Following a year long gestation period, the young probably become independent of their mothers at about one year of age, as is the case in most whales, with roughly a 73% chance of survival past year one. [15] [16]

The population status of the spade-toothed whale is entirely unknown.

Conservation

The spade-toothed whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU). [17] The species' IUCN Red List conservation status is "Data Deficient (DD)" [18] due to lack of information and uncertain data. [19]

Specimens

The sex of the 20th-century specimens is not known. By recovering or failing to recover DNA sequences of the Y chromosome, it could, in theory, be resolved. Little material is shared between the Pitt Island specimen and the calvariae, making direct anatomical comparisons problematic.

See also

Related Research Articles

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Beaked whales are a family of cetaceans noted as being one of the least-known groups of mammals because of their deep-sea habitat, reclusive behavior and apparent low abundance. Only three or four of the 24 existing species are reasonably well-known. Baird's beaked whales and Cuvier's beaked whales were subject to commercial exploitation, off the coast of Japan, while the northern bottlenose whale was extensively hunted in the northern part of the North Atlantic in the late 19th and early 20th centuries.

<span class="mw-page-title-main">Andrews' beaked whale</span> Species of mammal

Andrews' beaked whale, sometimes known as the deep-crest beaked whale or splay-toothed whale, is one of the least known members of a poorly known genus. The species has never been observed in the wild, and is known only from specimens washed up on beaches.

<i>Mesoplodon</i> Genus of beaked whales

Mesoplodont whales are 16 species of toothed whale in the genus Mesoplodon, making it the largest genus in the cetacean order. Two species were described as recently as 1991 and 2002, and marine biologists predict the discovery of more species in the future. A new species was described in 2021. They are the most poorly known group of large mammals. The generic name "mesoplodon" comes from the Greek meso- (middle) - hopla (arms) - odon (teeth), and may be translated as 'armed with a tooth in the centre of the jaw'.

<span class="mw-page-title-main">Hubbs' beaked whale</span> Species of mammal

Hubbs' beaked whale was initially thought to be an Andrews' beaked whale when discovered by ichthyologist Carl Hubbs; however, it was named in his honor when it was discovered to be a new species. This species has the typical dentition found in the genus, but its main outstanding features are a white "cap" on the head and very extensive scarring. The species is known from 31 strandings, a few at-sea sightings, and observations of two stranded whales that were kept in captivity for 16–25 days.

<span class="mw-page-title-main">Blainville's beaked whale</span> Species of mammal

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<span class="mw-page-title-main">Gervais's beaked whale</span> Species of whale

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<span class="mw-page-title-main">Ginkgo-toothed beaked whale</span> Species of mammal

The ginkgo-toothed beaked whale is a poorly known species of whale even for a beaked whale, and was named for the unusual shape of its dual teeth. It is a fairly typical-looking species, but is notable for the males not having any scarring.

<span class="mw-page-title-main">Gray's beaked whale</span> Species of mammal

Gray's beaked whale, sometimes known as Haast's beaked whale, the scamperdown whale, or the southern beaked whale, is one of the better-known members of the genus Mesoplodon. This species is fairly gregarious and strands relatively frequently for a beaked whale. In the Māori language, this species is called hakurā or iheihe.

<span class="mw-page-title-main">Hector's beaked whale</span> Species of mammal

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<span class="mw-page-title-main">True's beaked whale</span> Species of mammal

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<span class="mw-page-title-main">Pygmy beaked whale</span> Species of mammal

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<span class="mw-page-title-main">Stejneger's beaked whale</span> Species of mammal

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<span class="mw-page-title-main">Perrin's beaked whale</span> Species of mammal

Perrin's beaked whale is part of the toothed whale suborder and is one of over 90 known cetaceans in existence today. Beaked whales are part of the family Ziphiidae, which are the second most diverse group out of all marine mammals with over 20 species currently recognized. Although diverse, little is understood about these timid, deep divers that can dive for up to two hours. The whales are partially named after their beak shaped jaw, which extends from their small head. The genus name Mesoplodon comes from the Greek meanings of meso- (middle), - hopla (arms), - odon (teeth), and may be translated as 'armed with a tooth in the center of the jaw'.

<span class="mw-page-title-main">Southern bottlenose whale</span> Species of mammal

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References

  1. Pitman, R.L.; Taylor, B.L. (2020). "Mesoplodon traversii". IUCN Red List of Threatened Species . 2020: e.T41760A50383956. doi: 10.2305/IUCN.UK.2020-3.RLTS.T41760A50383956.en . Retrieved 11 November 2021.
  2. "Appendices | CITES". cites.org. Retrieved 14 January 2022.
  3. Hector, James (1873). "On the whales and dolphins of the New Zealand seas" (PDF). Transactions of the New Zealand Institute. 5: 154–170. Retrieved 6 November 2012.
  4. Gray, John Edward (1874). "Notes on Dr Hector's paper on the whales and dolphins of the New Zealand seas" (PDF). Transactions of the New Zealand Institute. 6: 93–97. Retrieved 6 November 2012.
  5. Hector, James (1878). "Notes on the whales of the New Zealand Seas" (PDF). Transactions of the New Zealand Institute. 10: 331–343. Retrieved 6 November 2012.
  6. Baker, Alan N.; van Helden, Anton L. (1999). "New records of beaked whales, Genus Mesoplodon, from New Zealand (Cetacea: Ziphiidae)" (PDF). Journal of the Royal Society of New Zealand. 29 (3): 235–244. doi:10.1080/03014223.1999.9517594. Archived from the original (PDF) on 7 October 2008. Retrieved 6 November 2012.
  7. Reyes, J.C.; van Waerebeek, K; Cárdenas J.C. & Yáñez, J.L. (1995): Mesoplodon bahamondi sp.n. (Cetacea, Ziphiidae), a new living beaked whale from the Juan Fernández Archipelago, Chile. Boletin del Museo Nacional de Historia Natural, Chile45: 31–44.
  8. 1 2 Platt, John R. Amazing: Rarest Whale Seen for First Time in History, but Not at Sea. Scientific American Blogs, 5 November 2012.
  9. Thompson, Kirsten; C. Scott Baker; Anton van Helden; Selina Patel; Craig Miller; Rochelle Constantine (6 November 2012). "The world's rarest whale". Current Biology . 22 (21): R905–R906. doi: 10.1016/j.cub.2012.08.055 . PMID   23137682.
  10. "First ever sighting of rare whale confirmed". CBC News. 6 November 2012. Retrieved 12 January 2014.
    "World's rarest whale seen for first time: Spade-toothed whale". Scientific American Blogs. 5 November 2012. Retrieved 12 January 2014.
  11. 1 2 van Helden, Anton L.; Baker, Alan N.; Dalebout, Merel L.; Reyes, Julio C.; van Waerebeek, Koen & Baker, C. Scott (2002): Resurrection of Mesoplodon traversii (Gray, 1874), senior synonym of M. bahamondi Reyes, van Waerebeek, Cárdenas and Yáñez, 1995 (Cetacea: Ziphiidae). Marine Mammal Science18 (3):609–621. PDF fulltext
  12. "Spade-toothed beaked whale". Whale & Dolphin Conservation USA. Retrieved 2 December 2020.
  13. "Marine Mammals of the World: A Comprehensive Guide to Their Identification by T. A. Jefferson, M. A. Webber and R. L. Pitman". Marine Mammal Science. 26 (2): 499–500. April 2010. doi:10.1111/j.1748-7692.2009.00358.x. ISSN   0824-0469.
  14. Dalebout, Merel L.; Ross, Graham J.B.; Baker, C. Scott; Anderson, R. Charles; Best, Peter B.; Cockcroft, Victor G.; Hinsz, Harvey L.; Peddemors, Victor & Pitman, Robert L. (2003): Appearance, Distribution, and Genetic Distinctiveness of Longman's Beaked Whale, Indopacetus pacificus. Marine Mammal Science19 (3): 421–461. PDF fulltext
  15. New, Leslie F.; Moretti, David J.; Hooker, Sascha K.; Costa, Daniel P.; Simmons, Samantha E. (17 July 2013). "Using Energetic Models to Investigate the Survival and Reproduction of Beaked Whales (family Ziphiidae)". PLOS ONE. 8 (7): e68725. Bibcode:2013PLoSO...868725N. doi: 10.1371/journal.pone.0068725 . ISSN   1932-6203. PMC   3714291 . PMID   23874737.
  16. New, Leslie F.; Moretti, David J.; Hooker, Sascha K.; Costa, Daniel P.; Simmons, Samantha E. (17 July 2013). Ropert-Coudert, Yan (ed.). "Using Energetic Models to Investigate the Survival and Reproduction of Beaked Whales (family Ziphiidae)". PLOS ONE. 8 (7): e68725. Bibcode:2013PLoSO...868725N. doi: 10.1371/journal.pone.0068725 . ISSN   1932-6203. PMC   3714291 . PMID   23874737.
  17. "Official webpage of the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region". Archived from the original on 16 March 2016. Retrieved 12 April 2012.
  18. Taylor, B.L.; Pitman, R.L. (August 2020). "Mesoplodon traversii". IUCN Red List of Threatened Species . August 2020: e.T41760A50383956. doi: 10.2305/IUCN.UK.2020-3.RLTS.T41760A50383956.en .
  19. Taylor, B.L.; Pitman, R.L. (August 2020). "Spade-toothed Whale – Assessment justification". iucnredlist.org. IUCN. Retrieved 21 September 2020.

Further reading