북극해에만 산다고 하여 '북극고
래'(Bowhead Whale)라고 불리는 고
래는 가장 큰 것이 130t(길이21m)이
나 된다. 남빙양에 주로 사는 대왕고
래(Blue Whale) 다음으로 큰 종류이
다.
최근 이 북극 고래의 壽命에 대한 연구가 진행되고 있다. 2007년 알라스카에 사는 에스키모들이 잡은 북극고래 몸에 작살의 파편이 박혀 있는 것이 발견되었다. 놀랍게도 이 작살은 1880년대에 제작된 것이었다. 이 작살의 사용연대와 북극고래의 생태를 종합적으로 조사한 결과 이 북극고래는 잡혔을 때 나이가 115~130살이란 결론에 이르렀다.
그때까지는 북극고래도 다른 고래들처럼 수명이 60~70살인 것으로 추정되었으나 최근 학자들의 연구결과 150~200살까지 산다는 사실이 확인되었다. 에스키모들은 북극고래가 인간보다 두 배나 산다는 이야기를 하곤 했는데, 사실로 입증된 것이다.
다른 고래들과 달리 북극고래는 大洋을 떠돌아다니지 않고 얼어붙는 북극해에서 산다. 두께가 50cm나 되는 얼음판을 뼈가 많은 머리로 깨어부수고 海面 위로 올라와 숨을 쉰다. 북극고래는 퉁퉁한 모습인데, 지느러미가 없는 것이 특징이다. 捕鯨이 시작되기 전 북극해엔 약5만 마리의 北極고래가 살고 있었으나 지금은 그 절반 수준이다.
북극고래를 잡아먹는 것은 인간과 솔피뿐이다. 그린랜드에 사는 에스키모인들은 생활용으로 북극고래를 잡을 수 있도록 허용되어 있다. 200살까지 살면서 바다를 유유히 떠도는 고래들은 인간을 우습게 여길지도 모른다. 북극고래 암컷은 90세가 될 때까지 아기고래를 出産한다고 한다.
| Bowhead Whale[1] | ||||||||||||||
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 Size comparison against an average human | ||||||||||||||
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| Scientific classification | ||||||||||||||
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| Binomial name | ||||||||||||||
| Balaena mysticetus Linnaeus, 1758 | ||||||||||||||
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-colored whale without a dorsal fin, it can grow to 20 meters (66 ft) in length. Estimated maximum weight of this thick-bodied species is 136 tonnes (134 LT; 150 ST), 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 24,900 worldwide, down from an estimated 50,000 before the commencement of whaling.
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[edit] Taxonomy
The Bowhead Whale was described by Carl Linnaeus in the 10th edition of his Systema Naturae (1758).[3] 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.[4]
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
The Bowhead Whale is a robust-bodied, dark-colored animal 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. This whale has a massive bony skull which it uses to break the ice from beneath to breathe. Some Inuit hunters have reported whales surfacing through 60 cm (24 in) of ice in this method. The Bowhead may reach lengths of up to 20 m (66 ft) 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 ft) for an unweighed giant caught off of Spitsbergen, Norway.[5]
[edit] Distribution
The Bowhead Whale is the only baleen whale that spends its entire life in and around Arctic waters. Those found off Alaska spend the winter months in the southwestern Bering Sea. It migrates northward in the spring, following openings in the pack ice, into the Chukchi and Beaufort seas, hunting zooplankton such as copepods. The Bowhead is a slow swimmer and usually travels alone or in small herds of up to six animals. Although it may stay below the water surface for as long as forty minutes in a single dive, it is not thought to be a deep diver.
[edit] Reproduction and lifespan
The Bowhead Whale is highly vocal and uses underwater sounds to communicate while traveling, feeding, and socializing. Some Bowheads make long repetitive songs that may be mating displays. The whales' behavior can also include breaching, tail slapping, and spyhopping. 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 1,000 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).[6]
In May 2007, a 50 ton specimen caught 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.[7][8][9]
Because of their possible lifespans, female Bowhead Whales are believed to go through menopause. Observations of very large animals without calves support this hypothesis.[10]
Plainly, maximum lifespan is not yet determined - but it may be the greatest of all mammals.
[edit] Population status
The Bowhead Whale has been hunted for its blubber, meat, oil, bones, and baleen. It is closely related to the right whales and shares with them 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.[citation needed] 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, 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. There are about 1,200 Bowheads off West Greenland (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 Bowhead population in the Eastern Arctic had undercounted the number of whales in the region, with a new estimate of 14,400 animals (r. 4,800-43,000).[11] These larger numbers would correspond to the estimates of the whale population before whaling, indicating that this population has recovered. However, some supporters of climate change could argue that with more breaking up of sea ice Bowhead whales could be threatened by increased shipping traffic.[12]
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] Behavior and predators
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Unlike most other baleen whales which primarily feed on concentrated shoals of prey species, the Bowhead Whale feeds in a manner similar to the Basking Shark by swimming forward with its mouths agape and continuously filtering water through its baleen plates. Thus, it specializes in feeding on much smaller prey items such as copepods. Its mouth with the large upturning lip on the lower jaw helps to reinforce and contain the baleen plates within its mouth, and prevents buckling or breakage of the plates due to the pressure of the water passing through them as it swims 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.
The Bowhead is social and nonaggressive, and will retreat under the ice when threatened. Its only predators are humans and the Orca. On rare occasions, the Bowheads are also attacked by sea lions.
