Balaenoptera acutorostrata

The Northern minke whale (Balaenoptera acutorostrata), is a very large cetacean, in the family of Rorquals (Balaenoptera). The Minke is a baleen whale, meaning that instead of teeth, it has long plates which hang in a row (like the teeth of a comb) from its upper jaws. Baleen plates are strong and flexible; they are made of a protein similar to human fingernails. Baleen plates are broad at the base (gumline) and taper into a fringe which forms a curtain or mat inside the whale's mouth. Baleen whales strain huge volumes of ocean water through their baleen plates to capture food: tons of krill, other zooplankton, crustaceans, and small fish.

The smallest of the rorqual whales (and the second-smallest baleen whale), the minke whale is also the most abundant. Two species are now recognised, the northern hemisphere minke whale (the subject of this species page) and the southern hemisphere Antarctic minke whale (Balaenoptera bonaerensis). Minke whales are slim in shape, with a pointed dolphin-like head, bearing a double blow-hole. The smooth skin is dark grey above, while the belly and undersides of the flippers are white, and there is often a white band on the flipper. When seen at close quarters, minke whales have variable smoky patterns which have been used to photo-identify individuals.

Minke whales feed on fish and various invertebrates; like all baleen whales they filter their food from the water using their baleen plates like sieves. Although largely a solitary species, when feeding minke whales can often be seen in pairs, and on particularly good feeding grounds up to a hundred individuals may congregate. A number of feeding techniques have been observed, including trapping shoals of fish against the surface of the water. After a ten month gestation period, births occur in mid-winter, at birth the calf measures up to 2.8 metres in length. It will be weaned at four months of age, and will stay with its mother for up to two years, becoming sexually mature at seven years of age. Minke whales have an average life span of around 50 years. Minke whales are rather inquisitive and often swim by the side of boats for up to half an hour.

The smallest of the rorqual whales, the minke whale is also the most abundant (2). Two species are now recognised, the northern hemisphere minke whale (the subject of this species page) and the southern hemisphere minke whale (Balaenoptera bonaerensis) (5). Minke whales are slim in shape (2), with a pointed 'dolphin-like' head (2), bearing a double blow-hole (5). The smooth skin is dark grey above, the belly and undersides of the flippers are white, and there is often a white band on the flipper (5) (6). When seen at close quarters, minke whales have variable 'smoky' patterns which have been used to photo-identify individuals (2).

Minke whales are the second-smallest baleen whales. They are identifiable by a narrow, pointy snout, and most seen in North American waters have a white stripe on the back of each flipper. Minkes are relatively common in coastal waters, where they feed on marine crustaceans and fish. They may also become the prey of killer whales. During spring and summer minkes generally migrate north through coastal waters. In fall and winter they go south, taking an offshore route. They tend to occur in small groups of two or three. Mature females can calve every year, after a gestation of about 10 months. Calves are born at any time of the year, but mostly in January and June. Newborns are less than 3 m long, nurse for 4 or 5 months, and take at least 6-7 years to mature.

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Mammal Species of the World

 The Minke is a medium sized whale, sleek in shape, with a very pointed head. It is dark grey to black in colour with a white underside and has white patches behind the head and a bright white band on the outer part of the flippers. Adults reach lengths of 6.75-10 m long and 5 -10 tonnes in weight. The new born calf is ca 2.5 m long and weighs ca 350 kg. There are 30-70 throat grooves that always end before the naval (umbilicus). The dorsal fin is sickle-shaped, and about two-thirds of the way back from the tip of the animal's snout. The tail flukes are a quarter of the animal's length in width, and are not shown when diving. There are 230-360 baleen plates, 12 -20 cm long, in each half of the upper jaw, which are yellowish-white at the front to grey-brown at the rear.The blow is very weak and can been seen at the same time as the dorsal fin appears. Spyhopping and breaching are common for this species, which forms small groups of up to 3 individuals. The Minke can remain submerged for up to 20 minutes (Kinze, 2002).

 This whale could be confused at a distance with the Sei whale and the Bryde's whale as they are relatively the same size, however the weak blow of the Minke whale and dorsal fin appearing at the same time as the blow is characteristic. At close range the white bands on the Minke's flippers are diagnostic (Jefferson et al., 1993; Kinze, 2002).

 Baleen whales are included in group species action plan under the UK Biodiversity Action Plan (Anon, 1999v). All baleen whales are protected under schedule 5 in the Wildlife and Countryside Act 1981, the Wildlife (Northern Ireland) Order 1985. All whales are listed on Annex A of EU Council Regulation 338/97 and therefore treated by the EU as if they are on CITES, Appendix I, thus prohibiting their commercial trade (Anon, 1999v). Whales are listed in Appendix I of CITES, Appendix II of the Bern Convention and Annex IV of the EC Habitats Directive (Anon, 1999v).

Antarctica, Azores Exclusive Economic Zone, Belgian Exclusive Economic Zone, Comores, Danish Exclusive Economic Zone, European waters (ERMS scope), Greek Exclusive Economic Zone, Gulf of Maine, Gulf of Mexico, Gulf of St. Lawrence, Kenya, Kenyan Exclusive Economic Zone, Madagascar, Mauritius, Mediterranean Sea, Mozambique, New Zealand Exclusive Economic Zone, North West Atlantic, Norwegian Exclusive Economic Zone, Portuguese Exclusive Economic Zone, Reunion, Seychelles, Somalia, Southern Bight, Spanish Exclusive Economic Zone, St. Lawrence Estuary, Subantarctic Waters, Tanzania, United Kingdom Exclusive Economic Zone, World Oceans

The common minke whale is a cosmopolitan species found in all oceans and in virtually all latitudes, from 65°S to 80°N. In parts of its range it is very abundant, in other parts much less so. Its migration patterns are poorly known. It occurs in the North Atlantic, the North Pacific, and the Southern Hemisphere, but is not known from the northern Indian Ocean.

North Atlantic
In summer, minke whales are common throughout the northern North Atlantic as far north as Baffin Bay, Greenland Sea, Svalbard (Norway), Franz Josef Land and Novaya Zemlya (Russian Federation), and as far south as 40°N (New Jersey) on the US east coast (Anon. 2005a), and as far south as the Hebrides (northwest British Isles) and the central North Sea in the east. In the mid-Atlantic summer concentrations of minke whales occur to at least as far south as 50°N (Sigurjónsson et al. 1991). It is likely that at least a part of the minke whale population over-winters in the summer range, but there has been very little observation effort in winter to confirm this.

Minke whales also occur south of this range in the southeastern North Atlantic, but with no obvious seasonality, and are not common, with the exception of the Canary Islands, where they appear to be frequent year-round (Van Waerebeek et al. 1999). There have been occasional sightings (Aguilar et al. 1983) and strandings (Van Waerebeek et al. 1999) off Spain and Portugal, Western Sahara, Mauritania and Senegal. Minke whales are rare in the Azores and not recorded from Madeira. The minke whale is considered a “visitor species” in the Mediterranean (average <1 record per year) with one vagrant recorded in the Black Sea (Reeves and Notabartolo di Sciara 2006).

There are very few winter records, but a summary by Mitchell (1991) indicates that they do occur in winter near Bermuda, the Bahamas and the Antilles, and the US coast south of 40°N. Ten strandings have been recorded in the Gulf of Mexico (Jefferson and Schiro 1997) but hardly any live sightings. A Norwegian winter expedition sent to the tropical Atlantic in 1989/90 to “find the breeding grounds of the minke whale” encountered just two minke whales, at 20°N and 10°N off West Africa in December (Folklow and Blix 1991).

North Pacific
Minke whales occur in summer right across the North Pacific north of about 30°N in summer, with a tendency for the distribution to shift northward in high summer. They are particularly abundant in the Okhotsk Sea in August (Miyashita et al. 1995), and also occur in the Bering Sea, around the Aleutian Islands and in the Gulf of Alaska (Moore et al. 2002, Zerbini et al. 2006) and the Chukchi Sea (Ivashin and Votrogov 1981). In the eastern North Pacific, there appears to be a year-round population off California and Baja California and in the Gulf of California, and minke whales occur in summer off Oregon, Washington and British Columbia (Anon. 2003). They have been seen off Hawaii but are not common there (Anon. 2005b).

In the western North Pacific, there are at least two distinct subpopulations: the so-called “J stock,” an autumn-breeding population that occurs in the Yellow Sea, East China Sea and Sea of Japan, with some penetration into the Okhotsk Sea in summer; and the O-stock which, like most baleen whales, breeds in winter, and occurs in summer in the northwestern Pacific, including the northeastern coasts of Japan, and in the Okhotsk Sea (Omura and Sakiura 1956, Kato 1992).

The winter distribution is poorly known. Japanese expeditions to look for wintering grounds in the southwestern North Pacific during 1993-95 failed to locate any minke whales (Miyashita et al. 1996). The timing of the arrival of minke whales in Korean and western Japanese waters is suggestive of migration from the south in spring and return in autumn (Ohsumi 1983). The wintering area in the eastern North Pacific has been identified acoustically to be primarily between 15 and 35 degrees N latitude (Rankin and Barlow 2005).

Southern hemisphere
Much of the data on the occurrence of minke whales in the Southern Hemisphere is ambiguous with respect to identification as B. acutorostrata or B. bonaerensis, because the two species are partially sympatric. Japanese scouting vessel data indicated high abundance of minke whales in November between 10°-30°S in the central South Pacific and in much of the eastern and southern Indian Ocean down to 50°S (Miyashita et al. 1995), but their species identity is unclear. The limited information available from surveys in low and middle latitudes from the 1987/88 season onwards, when the two species were reliably distinguished, indicates that most of the minke whales are B. bonaerensis (Nishiwaki et al. 1991), probably on route to the Antarctic from (as yet unknown) low-latitude breeding grounds, but also that B. acutorostrata is present in these latitudes.

Dwarf minke whales occur at higher latitudes but are much less common than B. bonaerensis. Of more than 1,700 minke whales taken by Antarctic pelagic whaling from the 1987/88 to the 1992/93 season (when the two species have been reliably distinguished), only 16 were dwarf minke whales (Nishiwaki et al. 2005). One was taken at 65°S and the remainder at between 55-62°S, the northern limit of whaling operations.

In coastal waters, dwarf minke whales have been recorded off most of the South Atlantic coast of South America (Baldas and Castello 1986, Zerbini et al. 1996), in the Beagle Channel (Chile/Argentina) (Acevedo et al. 2005), off South Africa (Best 1985), Australia (Arnold et al. 1987, Bannister et al. 1996, Arnold 1997), New Zealand (Dawson and Slooten 1990), and New Caledonia (Garrigue and Greaves 2001). The most northerly confirmed Southern Hemisphere record is from 2°S, off the northern coast of Brazil (Magalhães et al. 2007). Three dwarf minke whales were caught in whaling operations off Costinha, Brazil in 1980 (along with 900 Antarctic minke whales) (da Rocha and Braga 1982).

Minke whales have a worldwide distribution, appearing in all oceans and some adjoining seas. Cooler regions seem to be preferred over tropical regions.

Biogeographic Regions: arctic ocean (Native ); indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )

On a small note in Dubar (1828) was written that this species was stranded in Blankenberge (Belgium) in 1837
 (Dubar, J. (1828). Ostéographie de la baleine échouée à l'est du port d'Ostende, le 4 novembre 1827; précédée d'une notice sur la découverte et la dissection de ce Cétacée. Laurent Frères, Imprimeurs-Libraires: Bruxelles, Belgium. 61, 13 folded plates pp.)

circum-global

East Pacific; Eastern and Atlantic Ocean; Indo-West Pacific

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Throughout the world's oceans in tropical, temperate, and polar waters, including Hudson Bay (Can. Field-Nat. 106:266-267). See IUCN (1991) for further details. IWC stock management units have little or no biological significance (IUCN 1991).

Occurs in all oceans of the northern hemisphere from polar waters to tropical regions. The northern hemisphere minke whale is the whale most likely to be seen from the coasts of the UK and Ireland, particularly from Scotland, western Ireland and the Northern Isles (7). In the English Channel and southern parts of the Northern Sea it is rare (7).

Minkes are the smallest of the finback whales, growing to a maximum of 10.2 meters long. Females are larger than males, occasionally growing to a maximum of 10,000 kg. Coloration is dark above with a white underbelly. The head is pointed and bulletlike, with a relatively small rostrum. Baleen plates number around 300, are yellowish in color, and occasionally assymetrical in pattern. There are between 50-70 ventral grooves. A broad white band trims the dorsal side of flippers. The tail extends into two long tips. The dorsal fin is high and curved back.

Range mass: 6000 to 9000 kg.

Length: 9100 cm

Sexual Dimorphism: Females are larger than males.

Length:
Range: 6.7-9.8 m males; 7.3-10.7 m females

Weight:
Range: 20,000-40,000 kg

Distinguishing characteristics: white flipper patches. Blow not readily visible. Colour is light grey with white belly.

Habitat and Ecology

Systems

• Marine

Although not considered "coastal", these baleen whales rarely venture farther than 169 km from land. They also commonly enter estuaries, bays, fjords, and lagoons. They are also know to move farther into polar ice fields than other rorqual species.

Aquatic Biomes: coastal

inshore to offshore

Depth range based on 2687 specimens in 1 taxon.
Water temperature and chemistry ranges based on 1606 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): -1.678 - 29.313
  Nitrate (umol/L): 0.016 - 30.199
  Salinity (PPS): 30.771 - 37.050
  Oxygen (ml/l): 4.431 - 8.213
  Phosphate (umol/l): 0.044 - 2.073
  Silicate (umol/l): 0.494 - 87.652

Graphical representation

Temperature range (°C): -1.678 - 29.313

Nitrate (umol/L): 0.016 - 30.199

Salinity (PPS): 30.771 - 37.050

Oxygen (ml/l): 4.431 - 8.213

Phosphate (umol/l): 0.044 - 2.073

Silicate (umol/l): 0.494 - 87.652
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Habitat Type: Marine

Comments: Coastal and pelagic waters.

 An open water species, most often seen in coastal and inshore areas but sometimes enters inlets, bays or estuaries.

Inhabits inshore to offshore waters and is usually more concentrated in higher latitudes during the summer and lower latitudes during the winter, but migrations vary from year to year. This whale often enters estuaries, bays and inlets, and during summer may feed around headlands and small islands (2) (8)

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Many populations migrate to high latitude waters for summer, to low latitude waters for winter.

A baleen whale, this species feeds primarily on krill and some small fish. There are regional differences in the diet. Minkes eat krill almost exclusively in the Antarctic, but they are more omnivorous in the northern hemisphere, taking as food squid and small vertebrates such as cod, herring, and sardines.

Animal Foods: fish; mollusks; aquatic crustaceans

Foraging Behavior: filter-feeding

Primary Diet: carnivore (Eats non-insect arthropods)

Comments: Diet mostly fishes in North Pacific, krill in southern ocean, fishes (mainly) and krill in North Atlantic (IUCN 1991); fishes eaten are small, schooling species.

Usually solitary, sometimes found in groups of 2-3. Annual survival rate in Antarctic exceeds 90% (IUCN 1991). Common prey for orca (killer whale).

Comments: Active day/night.

Average lifespan
Status: wild: 45.0 years.

Average lifespan
Status: wild: 47.0 years.

Average lifespan
Status: wild: 50.0 years.

Maximum longevity: 50 years (wild) Observations: These animals have been estimated to live up to 50 years in the wild (Bernhard Grzimek 1990).

Only one young is born at a time. Gestation lasts for 10 to 11 months. Weight at birth is 450 kg. The young are weaned at 5 months, but they do not become sexually mature for 6 years. Females are thought to have young every other year. The breeding period is long--from December to May in the Atlantic and year round in the Pacific. Peak months for births are December and June. Growth stops at about 18 years for females and 20 years for males.

Breeding interval: Females are thought to have young every other year.

Breeding season: The breeding period lasts from December to May in the Atlantic and year round in the Pacific

Average number of offspring: 1.

Range gestation period: 10 to 11 months.

Average age at sexual or reproductive maturity (female): 6 years.

Average age at sexual or reproductive maturity (male): 6 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Average birth mass: 320000 g.

Average number of offspring: 1.

Average age at sexual or reproductive maturity (male)
Sex: male: 2740 days.

Average age at sexual or reproductive maturity (female)
Sex: female: 2740 days.

Gestation lasts 10-11 months. Single calf is born November-March in North Atlantic, mainly late May and early June in Southern Hemisphere. Young are weaned in 6 months or less. Adult females produce one calf every 1-2 years. Most sources give the age of sexual maturity as 6-7 years or 7-8 years, but 2 years or mean of 6-15 years also has been reported; age of maturity apparently decreases when populations are significantly reduced. Maximum age is about 30-40 years in the North Atlantic, something less than 50 years in the Southern Hemisphere.

The following is a representative barcode sequence, the centroid of all available sequences for this species.

There are 3 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 3
Specimens with Barcodes: 4
Species With Barcodes: 1

Genomic DNA is available from 1 specimen

Year Assessed

Assessor/s

Reviewer/s

Justification

History

• 1996
  Lower Risk/near threatened
• 1994
  Insufficiently Known
  (Groombridge 1994)

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N2 - Imperiled

Rounded Global Status Rank: G5 - Secure

Classified as Least Concern (LC) on the IUCN Red List (1). Listed on Annex IV of the EC Habitats Directive. All whales are listed on Annex A of EU Council Regulation 338/97 and are therefore classed as if they are listed on Appendix 1 of CITES. Under the Fisheries Act of 1981 whaling is illegal in UK waters. All cetaceans (whales and dolphins) are fully protected under the Wildlife and Countryside Act, 1981 and the Wildlife (Northern Ireland) Order, 1985. The UK recognises the authority of the International Whaling Commission in matters concerning whaling regulations (4).

Near Threatened.

Population

Population Trend

Major Threats

Comments: Some stocks (e.g., Sea of Japan/Yellow Sea/East China Sea stock and northeastern North Atlantic stock) have been depleted by commercial whaling (IUCN 1991). There is concern about the status of the West Greenland stock, where catches by local people for their own use continue (IUCN 1991). In the early 1990s, there was strong pressure from some countries to reopen commercial whaling for this species.

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, 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 minke whales, and indeed all cetacea, include pollution and reduction in prey abundance, perhaps as a result of over-fishing (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 (7).

Conservation Actions

This whale is a UK Biodiversity Action Plan priority species. Under Schedule 8 of the Wildlife and Countryside Act of 1981, this species is fully protected in UK waters. CITES (the Convention on International Trade in Endangered Species) controls exports of whale meat and products (7). In 1996, six tonnes of Norwegian whale meat was confiscated by customs officials in Japan. The shipment was disguised as mackerel (2). The current population figures for northern hemisphere minke whales are unknown and highly disputed. The future status of this inquisitive whale is unclear.

Minke whales have been hunted by people for products such as meat, oil, and baleen since the Middle Ages. Regardless, it has never been of large commercial importance until other whale species were overhunted. Annual kill peaked in 1976 with 12,398 individuals, but now is down to < 1,000. These are taken primarily by indigenous peoples for food, or by scientists for research.

Comments: Long hunted for human food and oil. Became a major target for modern whalers following depletion of larger species (around the 1930s in the Northern Hemisphere, 1970s in the Southern Ocean). Mainstay of Japanese factory ship whaling in southern ocean in early 1980s. Norway and Japan continued hunting for "scientific research" during recent whaling ban; these and possibly other nations have been pressing to resume commercial hunting of minke. See IUCN (1991) for review of exploitation history.

Least Concern (LC)