The minke whale is the smallest of the rorquals; females reaching a maximum length of approximately 10.5 m and males reaching 10 m. This whale has a sharply pointed, triangular rostrum, with a noticeable head ridge. The tall, sickle shaped dorsal fin is located in the end third of the body. Minke whales are dorsally dark gray and ventrally white, with grey shading extending up each side in front of and below the dorsal fin. The most distinctive marking is a brilliant white band across each flipper, generally visible when animals are near the surface (the band is not usually present on Antarctic minke whales). The minke whale has an inconspicuous blow. The ventral grooves commonly extend to just behind the flippers, and there are 231-285 pairs of baleen plates. Minke whales in the northern hemisphere are slightly smaller than those in the south.
There are three subspecies recognized. The North Pacific minke whale (B. a. scammoni) and North Atlantic minke whale (B. a. acutorostrata) both average about 8 m for adult males and 8.5-8.8 m for adult females. Both have the distinct white band on the flipper and possess white baleen plates. The dwarf minke whale (B. a. un-named subspecies) averages about 6.5-7.0 m as adults, and the white of the flipper extends up to the shoulder area. Dwarf minke whales only reach a known maximum of 7.8 m. Length at birth is 2.0-2.8 m. Maximum body weight is about 10 tons, although dwarf minkes weigh much less.
Can be Confused With
Other members of the balaenopteridae family (B. physalus, fin whale; B. musculus, blue whale; B. edeni, Bryde’s whale; etc.) are much larger than the minke whale. The minke whale is also distinguished by its sharply pointed rostrum and a low, inconspicuous blow. The dorsal fin often appears simultaneous to the blow as the animal surfaces to breathe. The best way to distinguish them (except in the Antarctic) is the presence/absence of the flipper band. Sei whales, Bryde’s whales, and some beaked whales may present identification problems if the animals are seen at a distance.
Minke whales have a cosmopolitan range and typically exploit rich polar or temperate waters in summer, all the way to edges of pack ice. In the winter, they move to warm equatorial waters, migrating thousands of kilometers. In some regions, minke whales are found year round. At least three populations of distinct geography are recognized:
North Pacific – In the eastern Pacific, they are found in the Bering and Chukchi Seas, on the shores of Alaska, and south to the coast of Baja California, occasionally being seen in the Sea of Cortez and the eastern tropical Pacific. In the western Pacific, minke whales are found from the Sea of Okhotsk and the Bering Sea in the north to the Sea of Japan and Yellow Sea in the south.
North Atlantic – In the eastern Atlantic, the minke whale is found from the Barants Sea and the coastlines of Norway and Iceland all the way south to the Azores, the shores of Portugal, and the Mediterranean Sea. In the western Atlantic, they can be found from the shores of Greenland and Newfoundland in the north to the waters of the Florida Keys and West Indies and the Gulf of Mexico in the south.
Southern Hemisphere – The minke whale in the southern hemisphere is pelagic and circumpolar, found from the pack ice of Antarctica in the summer to the South Atlantic, Indian, and South Pacific Oceans in winter.
Ecology and Behavior
Minke whales are highly migratory, inhabiting coastal waters. They prefer coastal and inshore waters to open ocean.
They are long-lived species, with a lifespan estimated at sixty years. Females become sexually mature at six to eight years and males at five to eight years. Evidence suggests calving can occur annually; given this life history, females are thought to be capable of rearing up to 40 calves each. Gestation lasts ten months, and birth occurs in winter at lower latitudes. Calves are thought to nurse three to six months. Minke whales sometimes aggregate for feeding in coastal and inshore areas of cold temperate to polar seas. Group sizes are generally small (singles, pairs, and trios), although several animals may aggregate on productive feeding grounds. Minkes do not fluke-up on a dive, but they do sometimes breach and perform other aerial behaviors. Minke whales may segregate into groups defined by age or gender.
Feeding and Prey
Minke whales use two forms of feeding: lunge feeding and bird-association feeding. Bird-association feeding involves foraging on fish concentrated below feeding birds.
Minke whales have a broad diet dominated by: Fish > crustaceans.
In the northern hemisphere, the minke whale prefers fish but eats krill when fish are not abundant; in the Southern Ocean minke whales feed on krill almost exclusively. Small schooling fish such as capelin, sandlance, and herring, as well as euphausiids, are particularly important prey items.
The minke whale is considered a species of “Lower Risk” (IUCN), and in the United States the species is protected by the Marine Mammal Protection Act. Population is approximately 125,000 in the northern hemisphere and 380,000 in the southern hemisphere. Minke whales have been heavily exploited, and this is now the species of whale most commonly taken by commercial and “scientific” whalers. It is still hunted by Norway in the North Atlantic and by Japan in the North Pacific, provoking international controversy. Despite this exploitation, the minke whale generally remains abundant in most areas of its range. Some are caught in fishing gear and suffer from vessel strikes and habitat disturbance.
Arnold, P., H. Marsh and G. Heinsohn. 1987. The occurrence of two forms of minke whales in east Australian waters with a description of external characters and skeleton of the diminutive or dwarf form. Scientific Reports of the Whales Research Institute 38:1-46.
Boyd, I.L., C. Lockyer and H.D. Marsh. 1999. Reproduction in marine mammals. pp. 218-287 in J.E. Reynolds III and S.A. Rommel, eds. Biology of Marine Mammals. Smithsonian Institution Press, Washington, DC.
Gaskin, D.E. 1982. The ecology of whales and dolphins. Heinemann, Portsmouth, New Hampshire.