The minke whale (), or lesser rorqual, is a species complex of baleen whale. The two species of minke whale are the northern common minke whale and the southern Antarctic minke whale. The minke whale was first described by the Danish naturalist Otto Fabricius in 1780, who assumed it must be an already known species and assigned his specimen to Balaena rostrata, a name given to the northern bottlenose whale by Otto Friedrich Müller in 1776. In 1804, Bernard Germain de Lacépède described a juvenile specimen of Balaenoptera acuto-rostrata. The name is a partial translation of Norwegian minkehval, possibly after a Norwegian whaler named Meincke, who mistook a northern minke whale for a blue whale.
Taxonomy
Most modern classifications split the minke whale into two species:
Common minke whale or northern minke whale (Balaenoptera acutorostrata) Antarctic minke whale or southern minke whale (Balaenoptera bonaerensis) Taxonomists further categorize the common minke whale into two or three subspecies: the North Atlantic minke whale, the North Pacific minke whale and the 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 (Scammon 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 recognized 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, the dwarf minke whale (first described by Best as "Type 3," 1985). On at least one occasion, an Antarctic minke whale has been confirmed migrating to the Arctic. In addition, at least two wild hybrids between a common minke whale and an Antarctic minke whale have been confirmed.
Description
The minke whales are the second smallest baleen whale; only the pygmy right whale is smaller. Upon reaching sexual maturity (7–8 years of age), males measure an average of 8.35 m (27.4 ft) and 7 t (6.9 long tons; 7.7 short tons) and females measure an average of 8.9 m (29 ft) and 8.25 t (8.12 long tons; 9.09 short tons) in length and body mass, respectively. Growth of females stops at 20–22 years of age, and the average length after this age is 8.8 m (29 ft). The estimated maximum size for females is over 10 m (33 ft) in length and more than 10–12 t (9.8–11.8 long tons; 11–13 short tons) in body mass. Males stop their growth at 18–20 years old. Common minke whales (Northern Hemisphere species) are distinguished from other whales by a white band on each flipper. The body is usually black or dark-gray above and white underneath. Minke whales have between 240 and 360 baleen plates on each side of their mouths. Minke whales typically live between 30–50 years, but in some cases, they may live for up to 60 years. They have a gestation and calving period of approximately 10–11 months and 2 years, respectively. In an 18-year study reported by Konishi in 2008, age was estimated through earwax analysis and found that the maximum lifespan of Antarctic minke whales was 59 years for females and 63 years for males. Minke whales have a digestive system composed of four compartments with a high density of anaerobic bacteria throughout. The presence of the bacteria suggests minke whales rely on microbial digestion to extract nutrients provided by their food. As with most Mysticetes, the auditory system for the minke whale is not well understood. However, magnetic resonance imaging suggests that the minke whale has fat deposits in the jaw intended for sound reception, much like Odontocetes. The brains of minke whales have around 12.8 billion neocortical neurons and 98.2 billion neocortical glia. Most of the length of the back, including dorsal fin and blowholes, appears at once when the whale surfaces to breathe. Despite its relatively large size, the minke whale is very fast, capable of swimming at speeds of 20–30 km/h (12–19 mph), and their surfacing can be sporadic and hard to follow.
Behavior
The whale breathes three to five times at short intervals before "deep-diving" for 2 to 20 minutes. Deep dives are preceded by a pronounced arching of the back. The maximum speed measured by methods such as satellite tracking or GPS was 20–30 km/h (12–19 mph). In a 2019 collaborative study involving scholars from around the world, various types of whales, including Humpback whales, Blue whales, Fin whales, Bryde's whales, and Antarctic minke whales, were tracked for four years to investigate changes in migration patterns based on size. When all results were finalized, most whales swam at an average speed of 1.9 m/s (6.8 km/h; 4.3 mph), but one Antarctic minke whale recorded a top speed of 8.3 m/s (30 km/h; 19 mph).
Migration Both species undertake seasonal migration routes to the poles during spring and towards the tropics during fall and winter. The difference between the timing of the seasons may prevent the two closely related species from mixing. A long-term photo identification study on the British Columbian and Washington coasts showed that some individuals travel as far as 424 km north in the spring, and 398 km south to warmer waters in the autumn. Many specifics about migration in this species still remain unclear.
Reproduction
The gestation period for minke whales is ten months, and calves measure 2.4 to 2.8 m (7.9 to 9.2 ft) at birth. The newborns nurse for five to ten months. Breeding peaks during the summer months. Calving is thought to occur every two years. The timing of conception and birth varies between region. In the North Atlantic, conception takes place from December to May with a peak month of February; while birth takes place from October to March with a peak in December. In the North Pacific off Japan, there appears to be two phases of conception, the majority of which occurs from February to March but also from August to September, with births occurring from December to January and June to July. In the Yellow Sea stock these two phases have not been noted, instead conception occurs from July to September and birth peaks from May to June. In the Southern Hemisphere conception takes place from June to December with a peak in August and September. Peak birth time occurs from July to August.
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