Berardius arnuxii
Arnoux's beaked whale

Berardius arnuxii has a circumpolar distribution in the southern hemisphere extending from the Antarctic coastline and ice edge (78° S) northward to about 34° S. Most records of sightings and strandings are south of 40° S, but some records occur farther north. A stranded individual was found as far north as 23° S off the coast of Brazil. It is assumed that B. arnuxii mostly occupies deeper, open ocean waters like its northern sister species Berardius bairdii, but there have been numerous sightings of B. arnuxii in shallower coastal waters (less than 500 m depth), and in close proximity to, as well as under, sea ice. Most strandings have occurred around New Zealand. (Balcomb III, 1989; Folkens et al., 2002; Hobson and Martin, 1996; Martuscelli, Milanelo, and Olmos, 2003; Ponganis, Kooyman, and Castellini, 1995)

Arnoux’s beaked whales are marine, open ocean dwellers, but they have also been seen in association with Antarctic sea ice and occasionally in shallower coastal waters. Their northern congener, Berardius bairdii, prefers deeper water where they dive to 1000 m to feed. Actual diving depths of B. arnuxii have never been recorded, but dive times of an hour or more indicate that they too may dive to depths of 1000 m. (Balcomb III, 1989; Folkens et al., 2002; Hobson and Martin, 1996; Kasuya, 1986; Ponganis, Kooyman, and Castellini, 1995; Stevick, McConnell, and Hammond, 2002)

Berardius arnuxii is one of the largest members of the family Ziphiidae ranging from 8 to 12 m in length, they are second in size only to Berardius bairdii. They have long, tubular bodies and blunt or rounded flippers. The dorsal fin is set far back on the body and is relatively small for a beaked whale (about 3% of the total body length). It has a straight leading edge and concave trailing edge. They have a prominent melon which slopes down into the distinctive ‘beak’ or ‘bottlenose’ of ziphiids. The lower jaw protrudes past the upper jaw. A pair of triangular shaped teeth are present on this protrusion while a second pair of peg-like teeth sit farther back behind a short diastema. These two pairs of teeth are characteristic of the genus Berardius and erupt in both males and females when the individual reaches sexual maturity. A deep V-shaped groove on the throat that consists of folds in the skin and blubber is also distinctive of Berardius. Their blow is a single small puff which is fairly indistinct. (Balcomb III, 1989; Folkens et al., 2002; Hobson and Martin, 1996)

Juveniles are slate grey, while older, sexually mature individuals range from very dark to light grey and are generally lighter on the head. Some individuals may appear brown or green colored due to diatoms attached to the skin. Numerous white scars are apparent on sexually mature individuals and seem to accumulate with time as older individuals have more scarring than their younger counterparts. A greater amount of scarring is also seen on larger individuals. The scars are linear or curved scratch marks occurring on the head, back and sides. Other scar types such as ovals and irregular patches are occasionally seen. No difference in scarring between males and females is apparent. Most of these marks are presumably caused by scratches from the protruding teeth of conspecifics and other objects in their environment such as rock and sea ice. See the Behavior section for more information on conspecific scarring. (Balcomb III, 1989; Folkens et al., 2002; Hobson and Martin, 1996; Kasuya, 1986)

Berardius arnuxii is almost identical in appearance to Berardius bairdii. The only real difference is the smaller size of B. arnuxii, but there is considerable overlap in size between the two species. However, the ranges of these two species do not overlap, which greatly simplifies identification. (Balcomb III, 1989; Folkens et al., 2002; Hobson and Martin, 1996)

Berardius bairdii can live to be 84 years old in males and 54 years old in females. Age in odontocetes (toothed whales) is determined by counting rings in the teeth, similar to the annual rings in a tree. Nothing is known about the lifespan of B. arnuxii, but it is assumed to be similar to that of B. bairdii. (Balcomb III, 1989; Boness, Clapham, and Mesnick, 2002; Folkens et al., 2002; Hohn and Fernandez, 1999)

Arnoux’s beaked whales are generally seen in groups of five to ten individuals, although larger temporary groups of up to 80 are sometimes observed. They seem to dive and then surface as a group. While at the surface they remain in close proximity to each other and respire for one to eight minutes or about 15 breaths. They slowly swim forward while respiring in the open ocean and remain mostly stationary while surfacing near ice. Average dive times are usually 10 to 45 minutes, but longer dives up to about 70 minutes also occur. They have been sighted near the pack ice edge and well into the pack ice in leads or open holes in the ice off the Antarctic coast. Some individuals have been trapped in closing ice and subsequently died, but it is unknown whether this is a common cause of mortality. (Balcomb III, 1989; Folkens et al., 2002; Hobson and Martin, 1996; Ohizumi et al., 2003; Ponganis, Kooyman, and Castellini, 1995; Stevick, McConnell, and Hammond, 2002)

Profuse scarring on mature individuals indicates some sort of social interaction between individuals, presumably aggressive. Most of the scars are linear and often parallel which corresponds with the exposed posterior teeth. One hypothesis for scarring in Berardius and other cetaceans is that it serves as a quality signal in competing males. This may apply to B. arnuxii, but the presence of scarring and teeth in both females and males may indicate that such displays are not limited to one sex. (Balcomb III, 1989; Folkens et al., 2002; Hobson and Martin, 1996; MacLeod, 1998)

Barardius arnuxii has a prominent melon and skull structure similar to other odontocetes, indicating that this species uses echolocation for signaling and sensory applications, but little is actually known. Hobson and Martin (1996) observed dolphin-like vocalizations in one group of individuals in ice leads. These clicks and squeaks were made while their heads were above the water line and seemed only to occur while their blowholes were closed. A study by Rogers and Brown (1999) on the acoustic traits of B. arnuxii found that these whales were "highly vociferous" exhibiting whistles, clicks, and click trains similar to other echolocators. (Balcomb III, 1989; Hobson and Martin, 1996; Rogers and Brown, 1999)

Little is known about the food habits of Berardius arnuxii and most information comes from comparison with B. bairdii. Berardius bairdii is primarily teuthophagous and piscivorous (squid- and fish-eating), but other benthic, epibenthic, and pelagic prey are also eaten. Berardius arnuxii is presumed to have a similar diet with slight variation due to the difference in geographic range. Their association with pack ice suggests that B. arnuxii may be exploiting a unique niche that is not available to most other cetaceans who do not have access to prey found under ice. (Balcomb III, 1989; Folkens et al., 2002; Hobson and Martin, 1996; Kasuya, 1986; Ohizumi et al., 2003)

There are no known predators of Arnoux’s beaked whales. However, killer whales (Orcinus orca) occasionally prey on Berardius bairdii in the northern hemisphere. As killer whales occur in the same range as B. arnuxii and utilize many of the same locations, it is possible that a similar relationship occurs, but evidence is currently lacking on this subject. (Balcomb III, 1989; Hobson and Martin, 1996; Stevick, McConnell, and Hammond, 2002)

Arnoux's beaked whales seem to act primarily as benthic predators. They are also hosts for several parasites such as nematodes, trematodes, cestodes, diatoms, cyamid amphipods, and occasional barnacles. (Balcomb III, 1989)

Although B. arnuxii may feed on species used by humans, they do not seem to have any significant impact on any fisheries. (Balcomb III, 1989; Folkens et al., 2002)

Encounters between humans and Berardius arnuxii are very rare. There is no commercial or subsistence harvesting of this species and they are not caught as by-catch in existing fisheries. (Balcomb III, 1989; Folkens et al., 2002)

Arnoux’s beaked whales are listed under the IUCN red list under the category LR/cd, but no specific threats are listed. They are listed in Appendix I of CITES but are not currently protected under the United States Endangered Species Act. The relatively few sightings imply that B. arnuxii is not common, but little is known regarding its abundance or potential threats. (Balcomb III, 1989; Folkens et al., 2002)

The only major differences between Berardius bairdii and B. arnuxii are the differences in size and range. Some researches claim that these two taxa represent one species with a disjunct distribution. Recent analyses of mitochondrial DNA have not resolved this ambiguity. In one study conducted by Dalebout et al. (1998) on the control region of the mitochondrial genome, only a 3.78% difference was found between B. arnuxii and B. bairdii. However, they had an extremely small sample size (two B. bairdii and one B. arnuxii). Despite high relatedness, these two taxa continue to be labled as separate species as is evident in later studies by Dalebout et al. (2004) and other researchers (Price et al. 2005). (Dalebout et al., 1998; Dalebout et al., 2004; Price, Bininda-Emonds, and Gittleman, 2005)