The minke whale, also known as lesser rorqual, is a complex species of baleen whale. There are two species of minke whale; the common minke whale (also known as the northern minke whale) (Balaenoptera acutorostrata) and the Antarctic minke whale (or southern minke whale) (Balaenoptera bonaerensis). Sometimes, 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.
Minke whales are the smallest of all the rorquals in the baleen family, with only the pygmy right whale being smaller. They belong to the family Balaenopteridae and the order Artiodactyla. 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.
It is one of the most abundant rorqual in the world, and their population status is considered stable throughout almost their entire range. Northern minke whales have a widespread distribution in the Northern Hemisphere and are found throughout the northern Atlantic and Pacific Oceans. Southern minke whales are found close to the polar region in the Southern Hemisphere, and are frequently found in areas off of Australia (such as the Great Barrier Reef), South America, and South Africa.
While minke whales are not currently endangered, whaling may have reduced populations in recent years. Keep reading on to find out more.
Minke Whale History
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 it 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.
Minke Whale Characteristics
Minke whales are the second smallest baleen whales. Both male and female minke whales typically weigh 4 to 5 tons at maturity and the maximum weight may be as much as 14 tons. Male minke whales reach a length of around 8 to 10 metres and females 8 to 10.5 metres.
The body of the minke whale is usually black or dark-grey above and white underneath. Most of the length of the back, including dorsal fin and blowholes, appear at the same time when the whale surfaces to breathe, which reveals the small size of the animal. Northern minke whales can be told apart from other whales by a white band on each flipper.
Minke whales have between 240 and 360 baleen plates on each side of their mouths. Their digestive system is composed of four compartments. There is a high density of anaerobic bacteria found in their stomachs, which suggests minke whales rely on microbial digestion to extract nutrients provided by their food.
Minke Whale Lifespan
The minke whale has an average lifespan of around 50 years, however, in some cases they may live for up to 60 years
Minke whales are primarily ichthyophagous (fish-eating) species, and will eat anchovies, dogfish, capelin, coal fish, cod, eels, herring, mackerel, salmon, sand lance, saury, and wolfish. However, they are opportunistic feeders and will also eat crustaceans, krill and plankton when available.
Minke whales feed by side-lunging into schools of prey and gulping large amounts of water.
Minke whales are usually found individually or in small groups of 2 to three, but loose groupings of up to 400 animals have been seen in feeding areas closer to the poles.
Minke whales are known to vocalize and create sounds that include clicks, grunts, pulse trains, ratchets, thumps, and recently discovered “boings”. These distinct vocalizations can vary depending on species and geographic area.
These whales have interesting breathing patterns. On surfacing from a deep dive, the whale breathes 3 to 5 times at short intervals before ‘deep-diving’ again for 2 to 20 minutes. Unlike other rorqual species, they do not raise their flukes out of the water when they are diving. Deep dives are preceded by a pronounced arching of the back.
Despite its large size, the minke whale can actually swim very fast. The maximum swimming speed of minkes has been estimated at 20 to 30 kilometres per hour. Minke whales are very tolerant and often approach vessels.
Minke whales undertake seasonal migration and can travel very long distances. Both whale species follow routes to the poles during spring and towards the tropics during fall and winter, but the difference between the timings of the seasons prevents them from ever mixing.
Immature whales are often more solitary and usually stay in lower latitudes during the summer months. Adult males will likely stay closer to the polar regions, whereas mature females will migrate farther into the higher latitudes.
Minke Whale Reproduction
Mink whales become sexually mature at around 3 to 8 years of age. The timing of conception and birth varies between region. The gestation period for these whales is 10 months and babies measure 2.4 to 2.8 metres (7 feet 10 inches to 9 feet 2 inches) at birth. Calves are usually born every two years. The newborns nurse from their mothers for five months.
The northern minke whale is found throughout the northern Atlantic and Pacific Oceans, while the southern minke whales are found in all oceans in the southern hemisphere, such as Australia, South America, and South Africa and the polar region.
Both species of minke whale prefer the coastal and the offshore waters of the oceans, but their distribution is considered cosmopolitan because they can occur in polar, temperate, and tropical waters in most seas and areas worldwide. They feed most often in cooler waters at higher latitudes.
The IUCN Red List labels the northern species as Least Concern and the southern as Near Threatened. The dwarf minke whale (B. acutorostrata subspecies) has no population estimate, and its conservation status is categorised as ‘data deficient’.
Predators and Threats
The most common predator of the minke whale is the killer whale (orca). However, there are other factors that threaten the minke whale population.
Minke whales have been threatened by commercial whaling since the 1930s. They were originally overlooked because of their small size, but these whales began to be targeted by China, Iceland, Korea, Russia, and Taiwan. To this day, Greenland, Japan, and Norway still hunt minke whales. They are taken as both animal and human food, as well as for scientific research.
Climate change is affecting whale populations as it has a direct effect on oceanographic conditions. As the conditions of the sea change, so does prey distribution could lead to changes in foraging behavior, nutritional stress, and diminished reproduction for minke whales. Temperature changes also affects the timing of environmental cues important for navigation and foraging in minke whales.
Minke whales are injured or killed in vessel collisions, too, and they can become entangled in fishing gear.