Minke Whale

Minke Whale

[ming-kee]
Minke Whale or Lesser Rorqual is a name given to two species of marine mammal belonging to a clade within the suborder of baleen whales. The Minke Whale was given its official designation by Lacepède in 1804, who described a dwarf form of Balænoptera acuto-rostrata.

Taxonomy

Most modern classifications split the minke whale into two species;

Taxonomists further categorize the Common Minke Whale into two or three subspecies; the North Atlantic Minke Whale, the North Pacific Minke Whale and Dwarf Minke Whale. All Minke Whales are part of the rorquals, a family that includes the Humpback Whale, the Fin Whale, the Bryde's Whale, the Sei Whale and the Blue Whale.

The junior synonyms for B. acutorostrata are B. davidsoni Cope 1872, B. minimia (Rapp, 1837) and B. rostrata (Fabricius, 1780). There is one synonym for B. bonaerensis - B. huttoni Gray 1874.

Writing in his 1998 classification, Rice recognised two of the subspecies of the Common Minke Whale - B. a. scammoni (Scammon's Minke Whale) and a further (taxonomically) unnamed subspecies found in the southern hemisphere to which he gave the common name the Dwarf Minke Whale (first described by Best, 1986).

Description

The minke whales are the second smallest of the baleen whales - only the pygmy right whale is smaller. Upon reaching sexual maturity (6-8 years of age), male and female minke whales measure an average of 6.9 and 7.4 metres (22'8" to 24' 3") in length, respectively. Estimates of maximum length vary from 9.1 m to 10.7 m (28'10" to 35'1") for females and 8.8 m to 9.8 m (28'8" 10" to 32'5") for males. Both sexes typically weigh 4-5 tons at maturity, and the maximum weight may be as much as 14 tons. The gestation period for minke whales is 10 months and babies measure 2.4 to 2.8 metres (7'10" to 9'2") at birth. The newborns nurse for five months.

Common minke whales (northern hemisphere variety) are distinguished from other whales by a white band on each flipper. The body is usually black or dark-grey above and white underneath. Most of the length of the back, including dorsal fin and blowholes, appears at once when the whale surfaces to breathe. The whale then breathes 3-5 times at short intervals before 'deep-diving' for 2-20 minutes. Deep dives are preceded by a pronounced arching of the back. The maximum swimming speed of minkes has been estimated at 20-30 km/h. Minke whales have between 240 and 360 baleen plates on each side of their mouths. Sexual maturity is reached at 7 or 8 years. Breeding peaks during the summer months. The gestation is 10 to 11 months and calving is thought to occur every two years. Minke whales typically live for 30-50 years; in some cases they may live for up to 60 years.

The brains of minke whales have around 12.8 billion neocortical neurons and 98.2 billion neocortical glia.

Population and distribution

Multimedia relating to the Minke Whale
Note that whale calls have been sped up to 10x their original speed.
The total population of Minke Whales is estimated to be in the order of 103,000 (95% confidence interval, IWC Scientific Committee 2008 ) in North East Atlantic. As of 2008, the estimates for Southern Hemisphere (CPIII with common Northern Boundaries) are 665,074 In the early 1990s the IWC Scientific Committee, after analysing the available data, agreed that Minkes in the Southern Hemisphere numbered 760,000 (CPII ), which the Japanese whaling industry currently uses as the (2005) estimate. In 2000, however, the Committee withdrew this advice in light of new survey data suggesting population estimates 50% lower than in the 1980s (Branch & Butterworth 2001). Final circumpolar estimates from the IWC IDCR/SOWER population surveys (1978/79-2003/04) were 338,000 and were only 39% of those from the 1985/86-1990/91 surveys, however, as of the 2008 Scientific Committee meeting, the figure of 665,074 was presented and discussed at the meeting and, subject to further analysis, will be the accepted 2008 population figure .The IWC has not yet decided whether these estimates reflect a real change in the population or simply a change in the survey methodology. Minke Whales are widely distributed throughout the world, commonly found from the poles to the tropics but prefer the open sea. The IUCN list the northern species as Lower Risk/Near Threatened and the southern as Lower Risk/Conservation dependent. CITES list both of the species in Appendix I (endangered) with the exception of the West Greenland stock, which is given in Appendix II (trade controls required).

The dwarf minke whale (B. acutorostrata subspecies) has no population estimate, and its conservation status is categorised as "data deficient".

Whaling

Whaling was mentioned in Norwegian written sources as early as the year 800 and hunting Minke Whales with harpoons was common in the 11th century. In the nineteenth century they were considered too small to chase, and received their name from a young Norwegian whale-spotter in the crew of Svend Foyn (died 1894) who harpoooned one mistaking it for a Blue Whale and was derided for it.

By the end of the 1930s they were the target of coastal whaling from countries including Brazil, Canada, China, Greenland, Japan, Korea, Norway, and South Africa. Minke Whales were not then regularly hunted by the large-scale whaling operations in the Southern Ocean on account of their relatively small size. However, by the early 1970s, following the over-hunting of larger whales such as the Sei, Fin, and Blue Whales, Minkes attracted the attention of these whalers too. By 1979 the Minke was the only whale caught by Southern Ocean fleets. Hunting continued apace until the general moratorium on whaling was introduced in 1986.

Following the moratorium, most hunting of Minke Whales ceased. Japan and more recently Iceland (in August 2003) have continued hunting for Minkes on scientific grounds, however, these "scientific grounds" are criticised by many environmental organisations as being a cover for commercial whaling. Both Iceland and Japan have the long term goal of resuming open commercial whaling. Although Norway initially followed the moratorium, they placed an objection to it with the IWC and resumed a commercial hunt in 1993. Norwegian whalers caught 639 in 2005. The quota for 2006 was set at 1052 animals, from which a catch of 546 was taken. The 2006 catch by Japanese whalers included 505 Antarctic Minke Whales. A 2007 analysis of DNA fingerprinting of whale meat estimated that South Korean fishermen caught 827 minke between 1999 and 2003. Japan plans to hunt 850 (plus/minus 10%) Antarctic minke whales in 2008.

Minke Whale-watching

Due to their relative abundance Minke Whales are often the focus of whale-watching cruises setting sail from, for instance, the Isle of Mull in Scotland, County Cork in Ireland and Húsavík in Iceland. Minke Whales are frequently inquisitive and will indulge in 'human-watching'. In contrast to the spectacularly acrobatic Humpback Whale, Minkes do not raise their fluke out of the water when diving and are less likely to breach (jump clear of the sea surface). This, combined with the fact that Minkes can dive under water for as long as twenty minutes, has led some whale-watching enthusiasts to label them 'stinky Minkes'. The name may also be applied because it is frequently possible to smell the breath of a Minke Whale whilst observing it from a boat.

In the northern Great Barrier Reef (Australia), a swim-with-whales tourism industry has developed based on the seasonal migration of dwarf minke whales during the months of June and July. A limited number of Reef tourism operators (based in Port Douglas and Cairns) have been granted permits by the Great Barrier Reef Marine Park Authority to conduct these swims, under the conditions that a Code of Practice is strictly adhered to, and that operators report details of all sightings as part of a monitoring program. Scientists from James Cook University and the Museum of Tropical Queensland have worked closely with participating tourism operators and the Marine Park Authority, researching potential impacts from tourism interactions on the whales and implementing management protocols to ensure that these interactions are ecologically sustainable.

Minke whales are also occasionally sighted in the Pacific waters, in and around the San Juan Islands of Washington State.

2007 Amazon incident

In November 2007, a Minke Whale ran aground on a sandbar in the Amazon jungle some from the ocean. Scientists said the whale was long and weighed about , and were working to dislodge the mammal and return it to the ocean. The whale ran aground on Wednesday near Santarem in Pará state, Brazil's Environmental Protection Agency said, according to BBC News. The whale's corpse was discovered the following Tuesday "by local people who reported it to the authorities."

Conservation status

According to the IUCN Red List, B. acutorostrata is considered "Near Threatened", whereas B. bonaerensis is "Conservation Dependent".

References

General references

  • Branch, T. A., and D. S. Butterworth. 2001. "Southern Hemisphere minke whales: standardised abundance estimates from the 1978/79 to 1997/98 IDCR/SOWER surveys". Journal of Cetacean Research and Management 3:143-174.
  • Minke Whales, Rus Hoelzel and Jonathon Stern, ISBN 1-900455-75-7
  • National Audubon Society Guide to Marine Mammals of the World, Reeves, Stewart, Clapham and Powell, ISBN 0-375-41141-0
  • Whale Watching in Iceland, Asbjorn Bjorgvinsson and Helmut Lugmayr, ISBN 9979-761-55-5
  • Whales & Dolphins Guide to the Biology and Behaviour of Cetaceans, Maurizio Wurtz and Nadia Repetto. ISBN 1-84037-043-2
  • Encyclopedia of Marine Mammals, editors Perrin, Wursig and Thewissen, ISBN 0-12-551340-2
  • Odin Norwegian Ministry of Foreign Affairs
  • "Modes of Production and Minke Whaling: The Case of Iceland", Gísli Pálsson (2000).

External links

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