Arnoux's beaked whale
Arnoux's beaked whales inhabit great tracts of the Southern Ocean.
The genus Berardius encompasses two species of beaked whale which have an antitropical distribution; 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. There has been some debate over whether these two forms represent distinct species or whether they are simply geographic variants. Several morphological characters have been suggested to distinguish them, but the validity of each has been disputed; 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.Berardius spp. 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 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.
Estimated lengths of live Arnoux's at sea have been up to 12 m (39 ft), but all dead specimens have been considerably smaller.
Their preferred diet is primarily deep-water squid, but also benthic and benthopelagic fish and some crustaceans, mostly taken near the sea floor. In a recent study, gouge marks in the seafloor were interpreted to be a result of feeding activities by beaked whales.
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.
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.