Bowhead Whale
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  Size comparison against an average human
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| Balaena mysticetus Linnaeus, 1758 |
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 Bowhead whale range
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The Bowhead Whale (Balaena mysticetus), also known as Greenland Right Whale or Arctic Whale, is a baleen whale of the right whale family Balaenidae. A stocky dark-coloured whale without a dorsal fin, it can grow to 20 metres (66 ft) in length. Estimated maximum weight of this thick-bodied species is 136 tonnes (152 tons), second only to the Blue Whale, although the Bowhead lags behind several other whales in maximum length. The Bowhead spends all of its life in fertile Arctic waters, unlike other whales that migrate for feeding or reproduction.
The Bowhead was an early target for the whaling industry, and its population was severely depleted before a whaling moratorium was introduced in 1966. The population is estimated to be over 11,700 worldwide, down from an estimated 50,000 before the commencement of whaling.
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[edit] Taxonomy
- See also: Evolution of cetaceans
The Bowhead Whale was described by Carolus Linnaeus in the 10th edition of his Systema Naturae (1758).[2] Balaena has remained a monotypic genus ever since. Leiobalaena, described by Eschricht in 1849, is a junior synonym.
The Bowhead Whale is an individual species, separate from the other right whales. It has always been recognized as such, and stands alone in its own genus as it has done since the work of Gray in 1821. There is, however, little genetic evidence to support this two-genera view. Indeed, scientists see greater differences between the members of Balaenoptera than between the Bowhead and the right whales. Thus, it is likely that all four species will be placed in one genus in some future review.[3]
It is thought that Balaena prisca, one of the five Balaena fossils from the late Miocene (~10 mya) to early Pleistocene (~1.5 mya), may be the same as the modern Bowhead Whale. Prior to these there is a long gap back to the next related cetacean in the fossil record, Morenocetus, which was found in a South American deposit dating back 23 million years.
[edit] Description
Bowhead Whales are robust-bodied, dark-coloured animals with no dorsal fin and a strongly bowed lower jaw and narrow upper jaw. The baleen plates, exceeding three meters and the longest of the baleen whales, are used to strain tiny prey from the water. The whales have massive bony skulls which they use to break the ice from beneath to breathe. Some Inuit hunters have reported whales surfacing through 60 cm (2 ft) of ice in this method. Bowheads may reach lengths of up to 20 metres and females are larger than males. The blubber layer of whale flesh is thicker than in any other animal, averaging 43–50 cm (17–20 in). The longest reported length for a Bowhead, was 21.2 m (70 feet) for unweighed giant caught off of Spitsbergen, Norway.[4]
[edit] Distribution
Bowhead Whales are the only baleen whales that spend their entire lives in and around Arctic waters. Those found off Alaska spend the winter months in the southwestern Bering Sea. They migrate northward in the spring, following openings in the pack ice, into the Chukchi and Beaufort seas, hunting zooplankton such as copepods. Bowheads are slow swimmers and usually travel alone or in small herds of up to six animals. Although they may stay below the water surface for as long as forty minutes in a single dive, they are not thought to be deep divers.
[edit] Reproduction and lifespan
Bowhead Whales are highly vocal and use underwater sounds to communicate while traveling, feeding, and socializing. Some Bowheads make long repetitive songs that may be mating displays. The whales' behaviour can also include breaching, tail slapping, and spy-hopping. Sexual activity occurs between pairs and in boisterous groups of several males and one or two females.
Breeding has been observed from March through August; conception is believed to occur primarily in March. Reproduction can begin when a whale is 10 to 15 years old. Females produce a calf once every 3 to 4 years, after a 13 to 14 month pregnancy. The newborn calf is about 4.5 m (15 ft) long and approximately 1000 kg (2,200 lb), growing to 9 m (30 ft) by its first birthday.
The lifespan of a Bowhead was once thought to be 60 to 70 years, similar to other whales. However, discoveries of antique ivory spear points in living whales in 1993, 1995, 1999 and 2007 have triggered further research based on structures in the whale's eye, leading to the reliable conclusion that at least some individuals have lived to be 150–200 years old (another report has said a female at the age of 90 was allegedly still reproductive).[5]
In May of 2007, a 50 ton specimen caught and harvested off the Alaskan coast was discovered to have the head of an explosive harpoon embedded deep under the blubber of its neck. Examination determined the 3 1/2 inch arrow-shaped projectile was manufactured in New Bedford, Massachusetts, a major whaling center, around 1890. This proof that it survived a similar hunt more than a century ago indicated to researchers that the whale's age was between 115 and 130 years old.[6][7][8]
Because of their possible lifespans, female Bowhead Whales are believed to go through menopause. Observations of very large animals without calves support this hypothesis.[9]
[edit] Population status
Bowhead Whales have been hunted for their blubber, meat, oil, bones and baleen. They are closely related to the right whale and share with it the hunting-ideal characteristics of slow swimming and floating after death. Before commercial whaling, there were over 50,000 Bowhead Whales in the north polar region (estimated)[citation needed]. Commercial whaling began in the 16th century, when the Basques hunted bowhead whales migrating south through the Strait of Belle Isle in the fall and early winter. In 1611 the first whaling expedition was sent to Spitsbergen, and by mid-century the population(s) there had practically been wiped out, forcing whalers to begin voyaging into the "West Ice"- the pack ice off the east coast of Greenland. By 1719 whalers had reached the Davis Strait, and by the first quarter of the 19th century Baffin Bay. In the North Pacific, the commercial whaling began in the 1840s, and within two decades over 60 percent of the Bowhead Whale population had been wiped out.
Commercial whaling, the principal cause of the population decline, has been discontinued. The population off Alaska has increased since commercial whaling ceased. Alaska Natives continue to kill small numbers of Bowhead Whales in subsistence hunts each year. This level of killing (25–40 animals annually) is not expected to affect the population's recovery. The Bowhead Whale population off Alaska's coast (also called the Bering-Chukchi-Beaufort stock) appears to be recovering but remains at about 10,500 animals (2001). The status of the other Bowhead populations is less well known. The Baffin Bay-Davis Strait population numbers about 1,200 (2006), while the Spitsbergen bowhead population may only number in the tens.
In March, 2008, Canada's Department of Fisheries and Oceans stated that previous estimates of the Eastern Arctic bowhead population had undercounted the number of whales in the region, with a new estimate of 14,400 animals, and perhaps as many as 44,000[citation needed]. These larger numbers would correspond to the estimates of the whale population before whaling, indicating that this population has recovered.
The Bowhead is listed in Appendix I by CITES (that is, "threatened with extinction"). It is listed as endangered under the auspices of the United States' Endangered Species Act. The IUCN Red List data is as follows:
- Spitsbergen population - Critically endangered
- Sea of Okhotsk subpopulation - Endangered
- Baffin Bay-Davis Strait stock - Endangered
- Hudson Bay-Foxe Basin stock - Vulnerable
- Bering-Chukchi-Beaufort stock - Lower risk - conservation dependent
[edit] Behaviour and predators
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This section needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (December 2007) |
Unlike most other baleen whales which primarily feed on concentrated shoals of prey species, Bowheads (and Right Whales) feed in a manner similar to Basking Sharks by swimming forward with their mouths agape and continuously filtering water through their baleen plates, thus they specialize in feeding on much smaller prey items such as copepods. Their mouth with the large upturning lip on the lower jaw helps to reinforce and contain the baleen plates within their mouth, and prevent buckling or breakage of the plates due to the pressure of the water passing through them as they swim forward. This is in contrast to the Rorquals which have distendable ventral pleats that they fill with water containing prey, which is then pushed out and filtered through the baleen plates in distinct batches.
Bowheads are social and nonaggressive, and will retreat under the ice when threatened. Their only predators are humans and orcas. Although on the rare occasion Bowheads are sometimes attacked by sea lions, that is practically unheard of though.
[edit] References
- ^ Cetacean Specialist Group (1996). Balaena mysticetus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 6 May 2006. Database entry includes a lengthy justification of why this species is dependent on conservation
- ^ (Latin) Linnaeus, C (1758). Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.. Holmiae. (Laurentii Salvii)., 824.
- ^ Kenney, Robert D. (2002). "North Atlantic, North Pacific and Southern Right Whales", in William F. Perrin, Bernd Wursig and J. G. M. Thewissen: The Encyclopedia of Marine Mammals. Academic Press, 806-813. ISBN 0-12-551340-2.
- ^ <Wood, The Guinness Book of Animal Facts and Feats. Sterling Pub Co Inc (1983), ISBN 978-0851122359>
- ^ Bowhead Whales May Be the World's Oldest Mammals
- ^ John C. George, Jeffrey Bada, Judith Zeh, Laura Scott, Stephen E. Brown, Todd O'Hara, and Robert Suydam (1999) Age and growth estimates of bowhead whales (Balaena mysticetus) via aspartic acid racemization. Can. J. Zool. 77(4): 571–580
- ^ 19th Century Weapon Found in Whale by ERIN CONROY - Associated Press
- ^ http://www.cnn.com/2007/TECH/science/06/13/century.old.whale.ap/index.html[dead link]
- ^ Rare Whales Can Live to Nearly 200, Eye Tissue Reveals
[edit] See also
[edit] External links
- Whale and Dolphin Conservation Society (WDCS)
- ARKive - images and movies of the bowhead whale (Balaena mysticetus)
- Bowhead Whale: Detailed Information from NOAA
- Harpoon may prove whale was at least 115 years old
- Eastern Arctic bowhead whales not threatened
