Species fact file
Common names: Common minke whale, lesser rorqual
Icelandic name: hrefna
Scientific name: Balaenoptera acutorostrata
Family: Balaenopteridae (rorqual whales)
Max length: 8.7m (males), 9m (females)
Distribution: Ice-free and non-enclosed seas of the North Atlantic
The name minke whale actually applies to two species – the common minke whale and the Antarctic minke whale. The common minke whale is the smallest species of baleen whale found in Iceland, and the second smallest in the world after the pygmy right whale. There are three subspecies of common minke – the North Atlantic minke whale, the North Pacific minke whale and the dwarf minke whale which is found in the southern hemisphere.
North Atlantic minke whales are dark grey with a white underside and distinctive white bands on the pectoral fins. Their small, curved dorsal fin is positioned two-thirds of the way down the back which gives the minke a distinctive profile when surfacing. Minkes typically surface a few times in quick succession before making a longer, deeper dive which can last 20 minutes or more. Their movements are often erratic, which can make them difficult to track – when they dive, it is almost impossible to predict where they will next come up for air!
Historically, minke whales were not favoured by whalers due to their small size. Today they are one of the few species of whales still hunted commercially, including in Iceland. Despite this they are the most abundant cetacean in Icelandic waters – an estimated 12,710 minke whales are found in Icelandic coastal waters during summertime. They are commonly sighted on whale-watching tours, especially in Faxaflói bay.
Like other rorquals, minke whales engage in lunge feeding. This is an energetic form of hunting where the whale swims at great speeds towards a ball of schooling fish or a dense aggregation of plankton, engulfing great mouthfuls of water and prey at a time. You can watch some footage of minke whales lunge feeding here.
Minke whales are mostly generalist hunters and do not appear to have one preferred prey type. Their diet varies by season and by region. There is evidence that minke whales in Iceland have switched prey in recent decades. It is thought that this may be linked to climate change as during the same period of time, there have been notable changes in water temperature and salinity in the waters around Iceland. While unlikely to affect large and warm-blooded marine mammals such as minke whales, smaller species that are low in the food chain are susceptible to these environmental changes. They may change how they are distributed or simply decline in abundance. As a result, the species available to minke whales as food have changed throughout time.
Sandeel, which was previously a major component of minke whale diet, is now consumed much less frequently. There has also been a decrease in the consumption of krill and capelin. On the other hand, herring and haddock have become important prey for minke whales.
As with most other baleen whales in Iceland, minke whales migrate seasonally. In summer, minke whales are found in sub-polar and cold temperate waters, including ice-free regions of the arctic. Their winter distributions are not fully understood, but minkes are known to leave their northern feeding grounds and migrate further south to warmer temperate and tropical regions.
Despite the geographic separation of the two species, there is evidence of at least one case of hybridisation between Antarctic and common minke whales in the northeast Atlantic. This is the first documented incidence of Antarctic minke whales in the northern hemisphere.
Unlike larger balaenopterids, minke whales don’t sing, but they do produce a range of vocalisations. These include grunts, thumps, and ‘down sweeps’ – sliding from a high frequency to a lower one. In the North Pacific minke whales make strange sounds described as ‘boings’. When scientists first heard this unusual noise recorded on hydrophones, they didn’t know where it came from – it was many years before they realised it had been the common minke whale all along!
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