Southern bottlenose whale

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Southern bottlenose whale. Source: South African National Antarctic Programme

Southern bottlenose whale (also Antarctic bottlenose whale; scientific name: Hyperoodon planifrons) is is one of 21 species of beaked whales (Hyperoodontidae or Ziphiidae), medium-sized whales with distinctive, long and narrow beaks and dorsal fins set far back on their bodies. They are marine mammals within the order of cetaceans.

20312 hyperoodon-frasercetus-planifrons.jpg Southern bottlenose whale. Source: Collection Georges Declercq
702px-southern bottlenose whale size.png Size comparison of an average human against a southern bottlenose whale. Source: Chris Huh

Conservation Status:

-IUCN Conservation Status - Least Concern.png.jpeg

Scientific Classification

Kingdom: Animalia
Phylum:--- Chordata
Class:------ Mammalia
Order:-------- Cetacea
Family:-------- Hyperoodontidae
Genus:--------- Hyperoodon
Species:-------- Hyperoodon planifrons (Flower, 1882)

Common Names:
Antarctic bottlenose whale
Flat-headed bottle-nosed whale
Flatheaded bottlenose whale
Flower's bottle-nosed whale
Flower’s bottle-nosed whale
Pacific beaked whale
Southern bottle-nosed whale
Southern bottlenose whale

Ziphiids have a pair of grooves on their throat that converge anteriorly to form a V pattern at the chin.

A large bottlenose whale can yield up to 200 kg of spermati oil, which is used in making ointments and fine, smokeless candles. Furthermore, it can yield up to 2000 kilograms of blubber oil, which is a base ingredient of numerous skin creams and cosmetic products.

Based on geological evidence, the Northern bottlenose whale and the Southern bottlenose whale probably diverged as recently as 15,000 years ago. (Mead 1989, Tinker 1988, Nowak, 1997)

Physical Description

Overview physical features are endothermic metabolism and bilateral symmetry. Southern bottlenose whale individuals grow to about eight meters in length. Sexual dimorphism is seen in this species, with the males averaging a length of 7.5 meters and females averaging only 6.5 meters. Characteristic species body mass has been estimated at six to eight tons.

The body of the Southern bottlenose whale is cylindrical in shape and tapers toward the tail in the last one third of its length. The tail flukes are wide and lack the notched center that is often seen in other cetaceans. Southern bottlenose whales have short, distinct beaks protruding from an inflated forehead or melon. In females and young males, the forehead slopes smoothly into the beak.

In older males, the forehead rises abruptly from the beak. The dorsal fin of the Southern bottlenose whale is located two thirds of the body length from the head, measures between 30 to 40 cm, and is sickle-shaped with a blunt tip. This whale's flippers are small, short, and also blunt-tipped.

Male Southern bottlenose whale have one pair of short, conical teeth which are situated at the tip of the lower jaw. Teeth are not found in the upper jaw. The teeth of females are either smaller or do not emerge at all. Rows of vestigial teeth are often present in the lower and upper jaw.

Southern bottlenose whales are a brownish-grey color on the head, back, dorsal fin, flippers, and tail . This color is paler on the belly, throat, and sides. However, coloration becomes lighter with age. Calves are a grayish-brown to black color, while older whales are completely yellowish-white in color. (Tinker 1988, Nowak 1997, Baker 1983, Minasian et al. 1984)

Behaviour

Key behaviors are: natatorial; motile; and social. Southern bottlenose whales generally stay well out to sea and are found in waters over 1000 meters in depth. Herds of Southern bottlenose whales are small, ranging from two to twelve. Hyperoodon planifrons travel and dive together as a very compact group, and dives may last up to 45 minutes.

A frequent behavior of Southern bottlenose whale is diving under ice and raising the beak clear of the water on the last surfacing before sounding. Interactions or contact with other species is uncommon for Southern bottlenose whale.

Little information is available about their mode of communication, but it is probably quite similar to the Northern bottlenose whale. A variety of sounds have been recorded for that species, which include a series of clicks and whistles used for echolocation and communication, respectively. (Nowak 1997, Minasian et al. 1984, Ponganis and Kooyman 1995)

Reproduction

Calving in Southern bottlenose whales occurs in the spring or summer. The young measure approximately three meters at birth. Very little information is known about the reproductive cycle of Southern bottlenose whales, but it probably resembles the cycle of its close relative, Hyperoodon ampullatus, Northern bottlenose whales. In that species, females probably give birth every two years, with a gestation period of 12 months. Weaning of young takes place after one year. Sexual maturity of female bottlenose whales is reached between the ages of 8-12, and in males, between 7-11 years of age. The life span of H. planifrons is at least 37 years. (Tinker 1988, Nowak 1997)

Key reproductive features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous .

Distribution and Movements

Distribution of Southern bottlenose whale.png.jpeg

The Southern bottlenose whale is found in the waters off of Australia, New Zealand, Brazil, Argentina, Tierra del Fuego, the Falkland Islands, South Georgia, the South Orkney Islands, South Africa, and the Pacific and Indian ocean sectors of Antarctica. Southern bottlenose whales have also been sighted near Sri Lanka. (Nowak 1997, Tinker 1988)

Habitat

The Southern bottlenose whale mainly stays in cooler waters and approaches the ice packs of Antarctica during the summer.

For the winter months, southern bottlenose whales migrate towards tropical waters (Minasian et al. 1984).

Feeding Habits

The Southern bottlenose whale is known to feed primarily on squid, and most likely, on fishes (Tinker 1988).

Primary Diet: carnivore (molluscivore ).

Animal Foods: fish; mollusks.

Economic Importance for Humans

There is very little economic importance attached to this species. The Southern bottlenose whale has never been subjected to systematic whaling, unlike its close relative, Hyperoodon ampullatus. (Tinker 1988, Minasian et al. 1984)

Threats and Conservation Status

The IUCN Red List reports:

Southern bottlenose whales are the most common beaked whales sighted in Antarctic waters, and are clearly abundant there. Kasamatsu and Joyce (1995) estimated an abundance of 599,300 (CV=15%) beaked whales south of the Antarctic Convergence in January, most of which were considered to be southern bottlenose whales. This estimate of abundance is likely underestimated because the methods used did not account for the fact that beaked whales dive for long periods and are inconspicuous when they surface (Barlow 1999). There is no firm information on trends in the global abundance of this species.

No significant exploitation of southern bottlenose whales is known, and they have never been hunted on a large scale. Although never taken commercially, some southern bottlenose whales have been killed during whaling for research purposes. Some have also been incidentally killed in driftnets (Croxall and Nicol 2004). Recently several of this species have been recorded as bycatch of driftnet fishing in the Tasman Sea. Numbers taken annually are not known, however, (Jefferson et al. 1993).

This species, like other beaked whales, is likely to be vulnerable to loud anthropogenic sounds, such as those generated by navy sonar and seismic exploration (Cox et al. 2006).

Developing high-latitude fisheries, such as that for Antarctic toothfish, have the potential to reduce food available for large predators, such as Hyperoodon planifrons. That this fishery has a significant illegal component is an additional concern.

Predicted impacts of global climate change on the marine environment may affect southern bottlenose whales, although the nature of impacts is unclear (Learmonth et al. 2006).

References

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Citation

Encyclopedia of Life (2011). Southern bottlenose whale. ed. C. Michael Hogan. Encyclopedia of Earth. National Council for Science and Environment. Washington DC. Retrieved from http://editors.eol.org/eoearth/wiki/Southern_bottlenose_whale