Species Profiles: minke whale
ContentsClassificationClass: Mammalia
Order: Cetecea Suborder: Mysticeti Family: Balaenopteridae Genus: Balaenoptera Species: acutorostrata Common names: Minke whale; piked whale; pikehead; lesser rorqual Irish Name: Droimeiteach beag; Míol mór mince top Key Identification FeaturesMax. adult body length/weight: 10m / 15 tonnes
Average adult body length/weight: 7m / 10 tonnes Average length/weight of calf at birth: 2.6m / 350kg Blow: The minke’s blow is a short quick 3m blow. It is generally not visible, unless seen at close range or in calm conditions, when it can be heard. Head: The head is narrow and sharply pointed, with a single ridge, which runs down the centre of the triangular shaped rostrum, beginning in front of the blowholes. This ridge resembles that of the fin whale, except that it is much sharper (hence the name sharp-headed finner). The rostrum is flattened. The baleen is short and is sometimes visible when a whale is feeding. Dorsal Fin: The dorsal fin is tall and falcate and is highly variable. It is positioned quite far forward, slightly less than 2/3 of the way back from the tip of the rostrum (as in the Sei whale). Pectoral Fins: Small and pointed (about 1/8 the total body length) and have a conspicuous white diagonal band (variable) on the upper surface. Colouration: Minke whales are black, brown, or dark grey on their backs and lighter on the belly and underside of the flippers. The most conspicuous feature of these animals in the Northern Hemisphere is a diagonal band of white on the upper surface of each flipper. The extent and orientation of the white band on the flipper varies individually. In the Southern Hemisphere, the presence and extent of the white flipper stripe is variable, and may not be present. Minke whales sometimes have a pale chevron on the back (like fin whales), behind the head and two regions of light grey on each side - one just above and behind the flipper, and another just in front of and below the dorsal fin. These may be conspicuous in some individuals and not in others. The tail flukes may be pale grey, bluish-grey or white on the underside, usually with a dark margin. The baleen plates are white, grey or cream in colour. There are 50-70 thin ventral pleats on the throat and belly, the longest of which end slightly anterior to the navel. Markings: Identification of individual minke whales is possible using a combination of naturally occurring features (shape of dorsal fin; scars; pigmentation) which vary between individuals. This technique has facilitated photo-identification studies of minke whales in some areas. top Field IdentificationThe dive sequence of the Minke whale is quite distinctive and aids identification from other easily confused species such as Sei, Fin or Northern Bottlenose whales. The sharply pointed snout, which breaks the water surface first and the sight of both blow and dorsal fin simultaneously distinguishes the Minke whale from all other rorqual whales with the exception of the Sei whale. The back and tail stock arch more strongly than the Sei whale as the Minke prepares for a long dive and the tail stock is strongly arched, but the flukes do not appear above the surface. The Minke whale also lacks the lower right hand jaw of the Fin whale.
If the animal you see is in the 20-30ft range, (too large to be a dolphin) and is showing no obvious blow, has a fair sized dorsal fin and does not fluke on diving, then you are most likely looking at a Minke whale. top Status and DistributionThe Minke whale is found virtually worldwide, and is less common in the tropics than in cooler waters. There are three geographically isolated populations currently recognised – in the North Pacific, North Atlantic and Southern Hemisphere. There are estimated to be between 500,000 to 1 million minke whales worldwide. top Reproduction and Life CycleMax. life expectancy: 40-50 years.
Average life expectancy: 45 years.Minke whales produce a calf every two years, and this calf is weaned after six months – the earliest known weaning period for any baleen species. Mating Occurs: January - May. Season of birth: December - January. Gestation: Approximately 10 months. top Conservation IssuesThe minke whales only known predator appears to be the killer whale and man. Although not endangered, some stocks of minke whales have been significantly reduced by whaling, particularly those in the central and eastern North Atlantic and the western North Pacific. The incidental capture of minke whales in fishing nets and traps may also be a cause for concern. The problem has been given little attention and its impact on populations has not been assessed. Contamination of the oceans by toxic, man-made chemicals and other pollutants may impact on minke whales, as has been suggested for other species. The effects of oil and gas exploration, other industrial activities, development of offshore wind turbines and shipping in the minke whale’s habitat along the Irish coastline, are largely unknown warranting further study. top |
 Where and When Best Seen in IrelandMinke whales can be seen off most headlands on the west and south west coastline of Ireland, less so in the Irish Sea. There appears to be a seasonal inshore migration of Minke whales off Loop Head during September and October but can be seen throughout the year. Minke whales have been stranded on every coastline in Ireland with the highest incidence of strandings on the south and south west coastlines.
In the years 1999-2001 they were, perhaps surprisingly, the 2nd most frequently observed baleen whale, after the fin whale. They are the 5th most frequently stranded cetacean in Ireland. top Stranded AnimalsThe general stout form of this slender whale aids in identification of stranded animals. The baleen plates are white, grey or cream in colour. There are 50-70 thin ventral pleats on the throat and belly, the longest of which end slightly anterior to the navel. There are between 270-348 short (up to 20cm long, 12 cm wide) baleen plates. The baleen is mostly yellowish white with fine white bristles and may be black or streaked towards the back. top BehaviourMinke whales are typically seen once and then may disappear for up to five minutes before reappearing in a totally different, unpredictable location, earning them the nickname: ‘slinky minke’. A typical breathing sequence consists of 5-8 blows at intervals less than a minute, followed by 3 – 8 shallow dives before a deep dive of typically 3- 5 minutes, but may last up to 20 minutes. Are often seen singly but may be seen in small groups of 3- 5 (up to 100, rarely), in good feeding areas. Minke whales are often difficult to approach but some, especially juveniles are inquisitive and may approach boats, appearing alongside without warning. Breaching behaviour is occasionally seen, particularly in stormy weather. They usually leave the water dorsal-side up at and angle of about 45° and re-enter, without twisting or turning their bodies, head first or with a belly flop. Most of the body may leave the water in the initial breach and the tail may sometimes be seen. Breaches are often repeated two or three times but may be repeated for long sequences. Can often be seen feeding near groups of seabirds. top Food and FeedingMinke whales have the most varied diet of all baleen whales, feeding on various small fish, including capelin, sand eel, herring and cod, they may also feed on small squid. In the Southern Hemisphere they feed exclusively on Krill. They hunt in a variety of ways often herding or chasing fish into a group before capturing them, driving fish from the deep to the surface, or by rushing through a group of fish and gulping them as they swim through, resulting in the capture of larger species such as cod and haddock. top |