Arnoux's beaked whale (''Berardius arnuxii''), also called the southern four-toothed whale, southern beaked whale, New Zealand beaked whale, southern giant bottlenose whale and southern porpoise whale is one of the species of ''

Berardius The four-toothed whales or giant beaked whales are beaked whales in the genus ''Berardius''. They include Arnoux's beaked whale (''Berardius arnuxii'') in cold Southern Hemispheric waters, and Baird's beaked whale (''Berardius bairdii'') in t ...

''. Arnoux's and

Baird's beaked whale Baird's beaked whale (''Berardius bairdii''), also known as the northern giant bottlenose whale, North Pacific bottlenose whale, giant four-toothed whale, northern four-toothed whale and North Pacific four-toothed whale, is a species of whale fro ...

s are so similar that researchers debated whether or not they are simply two populations of the same species, until genetic evidence and their wide geographical separation led them to be classified as separate. Little is known about their behavior due to infrequent encounters with live individuals.

Etymology

Named Berardius arnuxii in 1851 for the French surgeon, M. Arnoux, who presented the skull to the Paris Museum of Natural History in 1846.

Physical description

Arnoux's and Baird's beaked whales, have very similar features and would be indistinguishable at sea if they did not exist in disjoint locations. Both whales reach similar sizes, have bulbous

melons A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. It can also specifically refer to '' Cucumis melo'', commonly known as the "true melon" or simply "melon". The term "melon" can apply to both the ...

, and long prominent

beak The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for pecking, grasping, and holding (in probing for food, eating, manipulating and ...

s. Their lower jaw is longer than the upper, and once sexual maturity is reached the front teeth are visible even when the mouth is fully closed. The Baird's and Arnoux's beaked whales are the only whales in the Ziphiidae family where both sexes have erupted teeth. The teeth in the Ziphiidae are presumed to be used by males for fighting and competition for females. Ziphiidae have the most prevalent and pronounced markings caused by teeth scarring among the cetaceans. Front-facing teeth may be covered in barnacles after many years. Baird's and Arnoux's beaked whales have similarly shaped small flippers with rounded tips, and small dorsal fins that sit far back on their bodies. Adult males and females of both species pick up numerous white linear scars all over the body as they age, and these may be a rough indicator of age. These traits are similar in both sexes, as there is little

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

in either species. Among the observed differences in the sexes is their size: female Baird's and Arnoux giant beaked whales are slightly larger than the males.

Population and distribution

Arnoux's beaked whales inhabit great tracts of the

Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the world ocean, generally taken to be south of 60th parallel south, 60° S latitude and encircling Antarctica. With a size of , it is the seco ...

. Large groups of animals, pods of up to 47 individuals, have been observed off

Kemp Land Kemp Land is a thin sliver of Antarctica including, and lying inland from, the Kemp Coast. Part of the Australian Antarctic claim, it is defined as lying between 56° 25' E and 59° 34' E, and, as with other sectors of the Antarctic, is deemed ...

, Antarctica. Beachings in

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

and

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

indicate the whale may be relatively common in the Southern Ocean between those countries and

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

; sporadic sightings have been recorded in polar waters, such as in

McMurdo Sound The McMurdo Sound is a sound in Antarctica, known as the southernmost passable body of water in the world, located approximately from the South Pole. Captain James Clark Ross discovered the sound in February 1841 and named it after Lieutenant ...

. It has also been spotted close to

South Georgia South Georgia is an island in the Atlantic Ocean, South Atlantic Ocean that is part of the British Overseas Territories, British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. ...

and

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

, indicating a likely

circumpolar distribution A circumpolar distribution is any range (biology), range of a taxon that occurs over a wide range of longitudes but only at high latitudes; such a range therefore extends all the way around either the North Pole or the South Pole. Taxa that are al ...

. The northernmost stranding was at 34 degrees south, indicating the whales inhabit cool and temperate, as well as polar, waters. There is no stock report for the Arnoux's beaked whale to date by NOAA. An April 2022 sighting in the

Weddell Sea The Weddell Sea is part of the Southern Ocean and contains the Weddell Gyre. Its land boundaries are defined by the bay formed from the coasts of Coats Land and the Antarctic Peninsula. The easternmost point is Cape Norvegia at Princess Martha C ...

prompted a review of 108 prior sightings of 1125 individuals, dating to 1986-1998. This review corroborated their presumed range in the Southern Ocean, and found that Arnoux's beaked whales prefer the coasts of icy landmasses. In temperate regions above 60 degrees South, they can also be found near continents, even in

fjord In physical geography, a fjord (also spelled fiord in New Zealand English; ) is a long, narrow sea inlet with steep sides or cliffs, created by a glacier. Fjords exist on the coasts of Antarctica, the Arctic, and surrounding landmasses of the n ...

s far inland.

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).

References

{{Taxonbar, from=Q629227 Ziphiids Mammals of Brazil Mammals of Argentina Mammals described in 1851 Taxa named by Georges Louis Duvernoy