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Berardius arnuxiiArnoux's beaked whale

By Julia Turner

Geographic Range

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, et al., 2003; Ponganis, et al., 1995)

Habitat

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, et al., 1995; Stevick, et al., 2002)

Physical Description

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)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    8 to 12 m
    26.25 to 39.37 ft

Reproduction

The mating system of B. arnuxii is not known. Scarring on the bodies of males and females may indicate social aggression, possibly around mating, but these behaviors have not been observed.

Little is known about the mating and reproductive habits of Berardius arnuxii. Investigation of the sister species, B. bairdii, is informative, but information on the reproduction of this species is also sparse and debated. Berardius bairdii becomes sexually mature at about 8 to 10 years of age at lengths of 10 m for females and 9.5 m for males. Some researchers claim that females mature first while others state that males mature first and live longer than females. Males are more numerous and older based on research conducted on B. bairdii around Japan, but this could be due to a difference in geographical ranges between the sexes or sampling bias (Kasuya 1986). The gestation period is between 10 and 17 months with a three year interval between birthing events. Calving occurs mostly in the spring, but some births take place from late winter through summer and fall. The mating peak occurs from fall to early winter. Due to their smaller overall size and the few records of mature or pregnant stranded individuals, B. arnuxii seems to mature at younger ages and smaller sizes than B. bairdii. (Balcomb III, 1989; Boness, et al., 2002; Folkens, et al., 2002)

  • Breeding interval
    Breeding interval in B. arnuxii is unknown.
  • Breeding season
    Breeding seasonality in B. arnuxii is unknown.
  • Range gestation period
    10 to 17 months

Like all mammals, females B. arnuxii invest heavily in their young through gestation and lactation. Otherwise, little is known about parental investment in Arnoux’s beaked whales.

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female

Lifespan/Longevity

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, et al., 2002; Folkens, et al., 2002; Hohn and Fernandez, 1999)

Behavior

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, et al., 1995; Stevick, et al., 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)

Communication and Perception

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)

Food Habits

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)

  • Animal Foods
  • fish
  • mollusks

Predation

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, et al., 2002)

Ecosystem Roles

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)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

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)

Economic Importance for Humans: Negative

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)

Conservation Status

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)

Other Comments

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, et al., 2005)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Julia Turner (author), University of Alaska Fairbanks, Link E. Olson (editor, instructor), University of Alaska Fairbanks.

Glossary

Antarctica

lives on Antarctica, the southernmost continent which sits astride the southern pole.

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nomadic

generally wanders from place to place, usually within a well-defined range.

piscivore

an animal that mainly eats fish

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

ultrasound

uses sound above the range of human hearing for either navigation or communication or both

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Balcomb III, K. 1989. Baird's Beaked Whale Berardius bairdii Stejneger, 1883: Arnoux's Beaked Whale Berardius arnuxii Duvernory, 1851. Pp. 261-288 in S Ridgeway, R Harrison, eds. Handbook of Marine Mammals Volume 4: River Dolphins and the Larger Toothed Whales, Vol. 4. London: Academic Press.

Boness, D., P. Clapham, S. Mesnick. 2002. Life History and Reproductive Strategy. Pp. 278-283 in A Hoezel, ed. Marine Mammalogy Biology - an Evolutionary Approach. Oxford, UK: Blackwell Science.

Dalebout, M., C. Baker, J. Mead, V. Cockcroft, T. Yamada. 2004. A comprehensive and validated molecular taxonomy of beaked whales. Journal of Heredity, 96 (6): 459-638.

Dalebout, M., A. van Helden, K. van Waerebeek, C. Baker. 1998. Molecular genetic identification of southern hemisphere beaked whales (Cetecea: Ziphiidae). Molecular Ecology, 7: 687-694.

Folkens, P., R. Reeves, B. Stewart, P. Clapham, J. Powell. 2002. Guide to Marine Mammals of the World. New York: Alfred A. Knopf Inc..

Hobson, R., A. Martin. 1996. Behavior and dive times of Arnoux's beaked whales, Berardius arnuxii, at narrow leads in fast ice. Canadian Jounal of Zoology, 74: 388-393.

Hohn, A., S. Fernandez. 1999. Biases in dolphin age structure due to age estimation techniques. Marine Mammal Science, 15 (4): 1124-1132.

Kasuya, T. 1986. Distribution and abundance of Baird's beaked whales off the Pacific coast of Japan. Reports of the International Whaling Commission, 37: 61-83.

MacLeod, C. 1998. Intraspecific scarring in odontocete ceteceans: an indicator of male 'quality' in aggressive social interactions?. Journal of Zoology London, 244: 71-77.

Martuscelli, P., M. Milanelo, F. Olmos. 2003. First record of Arnoux's beaked whale (Berardius arnuxii) and Southern Right-whale dolphin (Lissodelphis peronii) from Brazil. Mammalia, 59 (2): 274-275.

Ohizumi, H., T. Isoda, T. Kishiro, H. Kato. 2003. Feeding habits of Baird's beaked whale Berardius Bairdii, in the western north pacific and Sea of Okhotsk off Japan. Fisheries Science, 69: 11-20.

Ponganis, P., G. Kooyman, M. Castellini. 1995. Multiple sightings of Arnoux's beaked whales along the Victoria land coast. Marine Mammal Science, 11 (2): 247-250.

Price, S., O. Bininda-Emonds, J. Gittleman. 2005. A complete phylogeny of the whales, dolphins, and even-toed hoofed mammals (Cetartiodactyla). Biological Reviews, 80: 445-473.

Rogers, T., S. Brown. 1999. Acoustic observations of Arnoux's beaked whale (Berardius arnuxii) off Kemp Land, Antarctica. Marine Mammal Science, 15 (1): 198-204.

Stevick, P., B. McConnell, P. Hammond. 2002. Patterns of Movement. Pp. 186-216 in A Hoezel, ed. Marine Mammalogy Biology - an Evolutionary Approach. Oxford, UK: Blackwell Science.

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