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Berardius

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Berardius
Size comparison of an average human against Arnoux's beaked whale
Size comparison of an average human against Baird's beaked whale
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Ziphiidae
Subfamily: Berardiinae
Genus: Berardius
Binomial name
Berardius arnuxii
Duvernoy, 1851
Arnoux's Beaked Whale range
Baird's Beaked Whale range

The genus Berardius contains two species of beaked whale, Baird's beaked whale and Arnoux's beaked whale. The two species are so similar, some scientists regard their separation into distinct species as a historical anomaly.[1] The two species are the largest of all beaked whales, and collectively they are sometimes referred to as the giant beaked whales.

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.[2] 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 specific name honors Dr. Maurice Arnoux, the ship's surgeon who found the skull of the type specimen on a beach near Akaroa, New Zealand.[3]

Physical description

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 shorter. Estimated lengths of live Arnoux's at sea have been up to 12 m (39 ft), but all dead specimens have been considerably smaller. 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. Both species pick up numerous white 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 two species' ranges do not overlap. This is perhaps the most significant reason they have historically been treated as separate species.

Arnoux's inhabit great tracts of the Southern Ocean. Beachings in New Zealand and Argentina indicate the whale is relatively common in the areas south of those countries south to Antarctica. 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. 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 of Japan on the west.

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

Behavior

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 10, 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. One interesting curiosity is that 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.

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)

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 individuals 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[4] by the Environmental Investigation Agency on 07 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;[5] however, the Mammalogical Society of Japan lists them as rare in Japanese coastal waters.

The Baird's beaked whale is listed on Appendix II [6] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II [6] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.

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

References

  1. ^ McCann (1975). "A study of the genus Berardius". Scientific Reports of the Whales Research Institute. 27. Tokyo, Japan: Whales Research Institute: 111–137. ISSN 0083-9086.
  2. ^ Sharks and Whales (Carwardine et al. 2002), p. 356.
  3. ^ Beolens, Bo, Michael Watkins, and Michael Grayson. 2009. The eponym dictionary of mammals. Baltimore: Johns Hopkins University Press, p. 38, 54.
  4. ^ "Video: Aftermath of a Japanese whale hunt". Retrieved 17 July 2010.
  5. ^ Template:IUCN2009.2
  6. ^ a b "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: 5th March 2009.
  • Giant Beaked Whales in the Encyclopedia of Marine Mammals pages 519-522 Teikyo Kasuya, 1998. ISBN 0-12-551340-2
  • National Audubon Society Guide to Marine Mammals of the World Reeves et al., 2002. ISBN 0-375-41141-0.
  • Whales, Dolphins and Porpoises Carwardine, 1995. ISBN 0-7513-2781-6
  • An image of a Baird's Beaked Whale at monteraybaywhalewatch.com
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