Arnoux’s beaked whale (Berardius arnuxii)
|Also known as:||Southern four-toothed whale|
|Spanish:||Ballena De Pico De Arnoux, Ballenato De Arnoux|
|Size||Head-body length: up to 9.9 m (2)|
Classified as Data Deficient (DD) on the IUCN Red List and listed on Appendix I of CITES (3).
One of the largest beaked whale species, Arnoux’s beaked whale is almost identical in appearance to its close relative, Baird’s beaked whale (Berardius bairdii), but is smaller in size (2). The body is uniform blackish-brown or dark grey, with irregular white blotches on the underparts of some individuals (2), and may be extensively scarred with single or paired rake marks made by the teeth of conspecifics (2) (4). The melon is relatively small, with a steep, almost vertical forehead, beneath which a short, tapering snout projects (2) (5). Interestingly, the lower jaw projects well beyond the upper jaw, so that the lower, front pair of large teeth is constantly exposed (2).
Arnoux's beaked whale is found in the southern Hemisphere, in a circumpolar distribution, from Antarctica as far North as southern Brazil and South Africa (1). Populations appear to be most concentrated to the south of New Zealand and South America (2)
Arnoux's beaked whale is usually found well-offshore, in deep, cold, temperate or sub-polar waters beyond the edge of the continental shelf (1) (2). Occasional sightings have also been made of this species in shallower coastal waters, and around seamounts and the continental slope (1). This species appears to be particularly well-adapted to living in ice-covered waters, and is frequently found around the Antarctic ice-edge and under pack-ice in the summer, but normally moves away from the ice-edge in winter (5).
As a result of the apparent rarity and open-ocean habitat of Arnoux's beaked whale, little is currently known about its biology (1) (5). Like other beaked whales, this species is an accomplished diver and, like Baird’s whale, probably forages on the sea-bed at depths of between 1,000 and 3,000 metres (4). The exceptional diving abilities of Arnoux's beaked whale also allow it to enter regions covered by sea ice, where it may travel up to seven kilometres between breathing sites, locating them with uncanny accuracy (1) (5). Such behaviour may offer the benefit of access to this species’ preferred diet of bottom-dwelling and pelagic fish and squid without competition from other predators (1) (5).
Although this species is generally encountered in groups of six to ten individuals, reports of congregations of as many as 80 have also been recorded (4)
A general lack of data about Arnoux's beaked whale means that its global population and conservation status are unclear. It is, however, generally thought to be rare and therefore may be adversely affected by some of the threats that are known to be causing declines in other beaked whale species. While this species is not generally targeted directly by commercial fisheries, it may be caught incidentally during drift-netting. In addition, commercial fishing in Antarctic waters may reduce food supplies for this species, particularly as a significant proportion of these fisheries are illegal and unregulated. Other issues may include climate change, as well as the use of active sonar by military vessels, which has been implicated in mass strandings of some beaked whale species (1).
Although it does not appear to be particularly threatened by hunting, Arnoux's beaked whale is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), which means that all international trade in this species in prohibited (3). In addition, this species is likely to benefit from the 1989 UN General Assembly resolution 44/225, which calls for effective conservation and management measures of living marine resources in areas of high seas drift-netting (1).
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- Conspecifics: individuals belonging to the same species.
- Melon: a lump of fatty tissue that forms the bulging forehead of toothed cetaceans (whales, dolphins and porpoises) thought to focus sound during echolocation.
- Pelagic: inhabiting the water column of the open ocean.
IUCN Red List (March, 2009)
- Nowak, R.M. (1999) Walker's Mammals of the World: Volume 2. Johns Hopkins University Press, Baltimore, Maryland.
CITES (March, 2009)
- Martin, A.R. (1990) Whales and Dolphins. Salamander Books Ltd, London.
Convention on Migratory Species (March, 2009)