The smallest of the rorqual whales, the common minke whale (Balaenoptera acutorostrata) is also the most abundant (2)(5). The common minke whale is slim in shape, and has a pointed, 'dolphin-like' head (2), bearing a double blow-hole (5). The smooth skin is dark grey above and white on the belly, and there is often a white band on each flipper (5)(6). When seen at close quarters, common minke whales have variable 'smoky' patterns which have been used to photo-identify individuals (2).
Until the 1990s, only one species of minke whale was recognised. However, minke whales have now been divided into two species, the common minke whale and the Antarctic minke whale (Balaenoptera bonaerensis). The common minke whale is believed to exist in two main forms, a northern hemisphere form and a southern hemisphere “dwarf” minke whale, which may be a separate subspecies(1)(5). Others have also further divided the northern hemisphere minke whale into North Pacific and North Atlantic populations (1).
Like all baleen whales, the common minke whale filters its food from the water using its baleen plates like sieves. The diet of this species includes fish and various invertebrates(1)(2).
Although largely a solitary species, common minke whales can often be seen feeding in pairs, and on particularly good feeding grounds up to a hundred individuals may congregate (2). A number of feeding techniques have been observed, including trapping shoals of fish against the surface of the water (7). Common minke whales are active, manoeuvrable and fairly inquisitive, often swimming by the side of boats for up to half an hour (2)(5).
The common minke whale gives birth in mid-winter, after a ten month gestation period (2). At birth, the calf measures up to 2.8 metres in length (5). Although it is weaned at four months of age (3), the calf stays with the female for up to two years, becoming sexually mature at seven years old (7). Common minke whales have an average lifespan of around 50 years (7).
The common minke whale occurs in both coastal and offshore waters. It is usually more concentrated in cooler, higher latitudes during the summer and warmer, lower latitudes during the winter, but in some areas it may be found year-round (1)(5).
The common minke whale is classified as Least Concern (LC) on the IUCN Red List (1). Most populations of common minke whale are listed on Appendix I of CITES, except the population from Greenland, which is listed on Appendix II (4).
The common name of this species indicates the main threat that has faced it for many years; Minke was an 18th Century Norwegian whaler who hunted small whales, flouting the whaling rules of the day (7). Despite the world moratorium on commercial whaling set up by the International Whaling Commission (IWC) in 1982, common minke whales are still hunted by Norway and Japan (2). Norway officially objected to the moratorium, and Japan kills whales for 'scientific research', but the carcasses are commercially processed after the research has been carried out (2).
Other potential threats facing the common minke whale, and indeed all cetaceans, include pollution and a reduction in prey abundance, perhaps as a result of over-fishing (5)(7). Entanglement in fishing nets and the effects of long-term climate change are also likely to pose problems, but as yet the importance of these threats is unknown (1)(5)(7).
The common minke whale is listed on Appendices I and II of CITES, meaning that international trade in this species should be strictly controlled (4). Although catch limits for all commercial whaling have been set at zero by the International Whaling Commission (IWC) since 1986, this does not apply to Iceland, Norway or the Russian Federation, and whaling permits have been issued to Japan for scientific research (1).
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