minke whale

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Last week on #WhaleWednesday you read about the Antarctic Minke whale this week you’ll learn about the Common (or Northern) Minke Whale

Minke whales are the smallest and most abundant of the rorqual whales. They have a sharply pointed snout, straight mouth line and a long ridge along the head with two blowholes. They have hundreds of baleen plates 20 to 30cm long growing from their upper jaws and between 50 and 70 pleats running from their throat and ending just past their flippers. These pleats stretch, allowing the whale to take in huge volumes of water when feeding. Minke whales have a streamlined shape and smooth skin with no callosities or barnacles. They are black, dark brown, or grey on their upper side with a lighter belly and a dorsal fin positioned far behind the centre of their back. Minke whales in the northern hemisphere have a white band on each flipper, though many in the southern hemisphere do not. The fluke of a minke whale is rarely seen above the surface.

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You are more likely to see minke whales at close quarters than other baleen whales because they are notoriously inquisitive and often approach boats.

The minke whale is the smallest of the rorqual whales. Females reach an average length of 8.5m and males grow to about 8m. Like other baleen whales, those found in the northern hemisphere tend to be smaller than those from the southern hemisphere. Minke whales weigh between five to 10 tonnes.

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The minke is widespread and seasonally abundant in the North Atlantic Ocean. In the winter, they migrate southwards, although it is unclear where their breeding grounds are located. In summer, concentrations shift northward to Spitsbergen and the Barents Sea, the coast of Norway and the waters off Iceland, Greenland and Newfoundland. In the northern Pacific, minkes are found in the Bering and Okhotsk Seas, and Gulf of Alaska in the spring and summer.

Like other great whales, minkes migrate to temperate and tropical waters in winter and polar waters in summer. Minke whales are often solitary, although they often travel in pairs or groups of three. In higher latitudes they are sometimes found in larger groups.

Common minke whales are generally solo marine mammals and prefer to travel alone, however in some cases they may be accompanied by one or two other whales. During small gatherings groups may expand to 4-10 minke whales but these occurrences are rare.

In the eastern North Pacific and North Atlantic, breeding may occur throughout the year, but there appears to be a calving peak in winter. The gestation period is believed to be around ten months. Females give birth to a calf every 12 to 14 months. Killer whales prey on minkes, as do other natural predators. They are believed to live to 40 to 50-years-old.

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Minke whales tend to feed on the food source that is most abundant in a given area, primarily krill and small schooling fish, but occasionally larger fish such as mature arctic cod and haddock. In the North Pacific, minke whales reportedly feed on euphausiids, copepods and sand eel, and those in the Okhotsk Sea feed on krill, and sometimes fish. In the North Atlantic, minke whales feed on a wide variety of prey, including sand eel, euphausiids, copepods, salmon, capelin, mackerel, and cod.

Northern minke whales are caught in the North East Atlantic by Norway pursuant to an objection to the International Whaling Commission’s (IWC) whaling moratorium, and by Greenlanders as “aboriginal subsistence” whaling. Japan hunts 150 whales a year in the North Pacific under their “scientific” reasearch permit. Japan also hunts up to 440 southern minkes a year in the Antarctic under their “scientific” research permit.

Minke whales are know to face attacks from groups of killer whales in areas where these predators are know to hunt other marine mammals. Numerous cases of minke whale meat being found in a killer whales stomach have been confirmed along with injuries and scares being observed on minke whales that have successfully escaped being killed. There are also a number of cases where dead minke whales have been spotted eaten by groups of sharks which my indicate that they are either hunted by sharks or the sharks wait for the whale to die and then consume the carcass.

The common minke whale global population however is currently under review by the IWC whilst little information is available for the dwarf minke whale. The species is listed as of Least Concern by IUCN (2008).

Video: Bait Ball – Common Minke Whale lunge feeding

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The minke whale is the smallest rorqual whale and, as such, was the last to be targeted by whalers. Until the turn of the century, the minke was treated as one species but it is now widely accepted that there are two species: a common minke and an Antarctic minke whale. The latter overlaps in its distributional range with a small form of the common minke, sometimes called the dwarf minke whale.

The Antarctic minke whale is among the smallest of the baleen whales, with only the common minke and the pygmy right whale being smaller. Males can reach a length of 35 ft and females approximately 32 ft in length, and adult minke whales can weight up to 15 tonnes.

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The body colour is usually black or dark brown with streaks of paler colour on their lateral sides, and a distinctly paler belly. It has a notably pointed rostrum and a single ridge on its head. This species often has a yellow wash to its baleen as a result of diatom growth. Most importantly, the Antarctic minke lacks the distinctive white flipper mark that is found in the common minke whale.

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Antarctic minke whales are known from around 7º S to the ice edge (and into the ice fields) during the austral summer (November through March). There they feed mainly on krill and, in turn, are important prey items for the orca that also live in these waters. They will occasionally approach smaller boats when feeding. The Antarctic minke whale is usually found alone or in pairs, although aggregations of hundreds of whales can gather in feeding grounds.

The antarctic minke whale reaches sexual maturity at 7 to 8 years old and has a lifespan of approximately 50 ears. The species mates over the winter and the female undergoes a 10 month gestation period, usually giving birth to a single calf, although twins and triplets may sometimes occur. The calf typically suckles for 5 months before being weaned, and will remain with the female for up to 2 years.

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Distribution Map: Minke whales are the only baleen whale species which is still most common in Antarctic waters and the most ice adapted of the Antarctic baleen whales. They have been seen hundreds of kilometers into heavy pack ice in the middle of winter and some of them obviously spend winter there. In summer, their favourite habitat seems to be open pack ice, that is, pack ice where there is quite a lot of open water among ice floes.

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Minke whales (both Antarctic and common) continue to be hunted in large numbers by the Japanese whaling fleet, who claim to kill minke whales for “scientific research”, but they are simply attempting to recommence commercial whaling. The meat from this research is sold in commercial markets. Since 2005 Sea Shepherd Conservation Society has used its ships to disrupt Japan’s annual whaling expedition in Antarctic waters. (Be sure to check out the TV series Whale Wars) However this year, Sea Shepherd has announced it is suspending the campaign, since the Japanese whalers have doubled their whaling grounds and are now employing military surveillance to watch Sea Shepherd ship movements in real time by satellite. The result is that Sea Shepherd cannot compete with their military grade technology. Captain Paul Watson, founder of Sea Shepherd Conservation Society, has stated that Sea Shepherd will regroup with different strategies, tactics and an alternative way to dealing with the Japanese whalers.

Like other cetaceans, the Antarctic minke whale is also vulnerable to chemical and noise pollution. Climate change will also be a major threat to this species. With rising temperatures, a reduction of sea ice means the Antarctic minke whale may lose between 5 and 30 percent of ice associated habitat in the next 40 years. As the area of suitable habitat reduces and prey populations decrease there will be an increase in competition for space and food, ultimately decreasing the population of this whale species.

They are categorized as Data Deficient by the IUCN Red List (2008).

Video: Curious Antarctic Minke Whale