Minke Whales are one of the smallest and most abundant of the baleen whales. Only the Pygmy Right Whale are smaller.
There are considered to be two species of Minke Whales, the Common (or Northern) Minke Whale (Balaenoptera acutorostrata) and the Antarctic Minke Whale (Balaenoptera bonaerensis) which was recognised as a separate species in 2001.
Further to this the Common Minke whale has been divided into several subspecies, the North Atlantic Minke Whale, the North Pacific Minke Whale. There is also the Dwarf Minke Whale which is currently regarded as an undescribed subspecies of Common Minke whale. The Dwarf Minke whale was first described by PB Best in 1985 and given its name by DW Rice (Marine Mammals of the World) in 1998. There is ongoing debate around the Dwarf Minke Whale being a third separate species or not?
All Minke whales are part of the Rorqual family which also includes Humpback, Fin, Sei, Bryde’s and Blue whales.
Antarctic Minke Whale by Rachel Hardman
Antarctic Minke Whales Common Name: Antarctic Minke Whales Other Names: Southern Minke Whale, Dark-shoulder Minke Whale, Pike Whale, Ordinary Minke Whale, Scammon’s Minke Whale Scientific Name: Balaenoptera bonaerensis Conservation Status: Near Threatened Length: New-born calf up to 2.8 metres, Adults females up to 8 metres, Males up to 6.9 metres. (Maximum up to 9.8 metres) Weight: Birth weight is under 1 ton. Adults up to 4-5 tonnes. Gestation: 10 months Weaning Age: Approximately 10 to 12 months Calving Interval: 2 years Sexual Maturity Age: Females Approx 7.9 m and 7-8 years, Males Approx 7.3 m and 8 years Physical Maturity Age: Mating Season: June to Dec (peak in August and September) Calving Season: July to August Cruising Speed: 20 kilometres per hour cruising and up to 35 kilometres per hour for short bursts Protected Since:
Dwarf Minke Whales Common Name: Dwarf Minke Whales Other Names: Scientific Name: Balaenoptera acutorostrata Conservation Status: Length: New-born calf 2 metres, Adults up to 8 metres. Weight: Birth weight is less than 1 ton. Adults up to 5 tonnes. Gestation: 11 months Weaning Age: 6 months Calving Interval: Sexual Maturity Age: Physical Maturity Age: Lifespan: 30–50+ years Mating Season: Calving Season: April to June Cruising Speed: 20 kilometres per hour cruising and up to 40 kilometres per hour for short bursts Protected Since:
Field Identification – Dark grey in colour with light grey and white markings. – Bushy shaped blow of about two meters height. – Dolphin shaped fin on their backs. – Triangular hump two thirds of the way along their backs. – Tail fluke thick and triangular in shape.
The two species found in the Southern Hemisphere, the Antarctic and the Dwarf Minke Whales. The Antarctic is the larger of the two and does not have a white band across its peck fin and shoulder (blaze) as the Dwarf Minke Whales do.
Taxonomy Up until recently it was thought that only one species of Minke Whale existed, referred to as B. acutorostrata. Now it is generally accepted that two species exist, the Common Minke Whale (B. acutorostrata) and the Antarctic Minke Whale (B. bonaerensis).
The Common Minke Whale has been further divided into two to three subspecies; the North Atlantic Minke Whale, the North Pacific Minke Whale and the Dwarf Minke Whale.
Rice in his 1998 classification recognised two of the subspecies of the common minke whale – B. a. scammoni (Scammon’s minke whale) and another subspecies found in the Southern Hemisphere, the Dwarf Minke Whale (first described by Best as “Type 3”, 1985). There is ongoing debate around the Dwarf Minke being a third separate species or not?
Description Minke Whales are fast, active and highly manoeuvrable whales that are beautifully shaped and coloured, particularly the Dwarf Minke Whale. They are the second smallest of the baleen whales with only the Pygmy Right Whale being smaller.
Minke Whales have a beautifully streamlined body with a very narrow and pointed rostrum that has a single ridge. Minke whales have between 240 and 360 baleen plates on each side of their mouths. They trend to surface nose first with a small bushy blow about two metres in hight. Once on the surface you will be able to see most of their length including most of their back, blowhole and dorsal fin. The dorsal fin is a tall falcate shape (sickle-shaped) and positioned relatively far forward on the middle third of the body. When preparing to deep dive they will expose and arch their backs but do not raise their tails from the water. They can dive for up to 20 minutes. Minke whales are known to be very curious and will often approach boats. In short bursts they can travel at almost 40kmp and have been known to create an almost roster tail like wake.
Minke Whale Size by Chris_huh/Wikimedia Commons
The two species found in the Southern Hemisphere, the Antarctic and Dwarf Minke Whales. The Antarctic is the larger of the two. At birth Minke Whales are about 2.8 m in length, and grow at a rate of approximately 1 cm per day while suckling. Adult males measure an average of 6.9 m and females 8 m in length, respectively. The maximum length of Antarctic Minke Whales appears to be around 9.8 metres. They will reach sexual maturity at around 6–8 years of age. Minke whales will typically live for 30–50 years, perhaps even as long as up to 60 years. Both sexes typically weigh around 4–5 tons at sexual maturity with a maximum weight at as much as 10 tons.
Minke Whales are the most colourful of all the baleen whales with complex patterns of white, light and dark greys. These patterns are the easiest way to tell the different species apart.
Common or Northern Minke Whale (Northern Hemisphere) are a dark grey on top with a white belly underneath. Their most distinct makings is a white band across each peck fin.
Antarctic Minke (Southern Hemisphere) is slightly larger than the Common and Dwarf Minke and do not have the dark throat, white band on the peck fins or white shoulder blaze (patches). Their backs are dark bluish-grey, with pale grey to white sides and belly. Undersides of their peck fins and tails are white. They also have asymmetrically coloured baleen, with the right side series having a larger number of white plates towards the front of the head than on the left.
Dwarf Minkes (Southern Hemisphere) is the smallest of the species and has a distinctive white shoulder blaze (dark at the tip of peck fin and completely white where fin joins body). They also have a triangular shaped thorax patch extending up from the peck fin and shoulder. A dark band extends down the neck between the mouth and peck fin which continues down the sides onto the throat.
Lizard Island on the Great Barrier Reef, Qld
Distribution and Movement Patterns Antarctic Minke Whales and Dwarf Minkes are found across the Southern Hemisphere’s waters from the tropics too deep in the Southern Ocean. Each year they will undertake long and extensive migrations from their summer Antarctic feeding grounds to their winter sub-tropical to tropical breeding grounds. They have even been spotted up to 350 km south of the ice edge during winter, suggesting that some of the population may over-winter in Antarctica.
Australia – Antarctic Minke Whales have been recorded in the waters of all states except the Northern Territory although their exact range is not yet completely understood. Antarctic Minke Whales are not that gregarious and tend to be found alone or in pairs. It is thought that the Antarctic Minkes do not travel as far north as the Dwarf Minke Whales. During the summer months they can be found feeding along the Antarctic sea ice edge where they form into larger feeding pods. Their winter breeding grounds appear to off the continental shelf edge off mainland Australia although due to a lack of observations estimations of populations and their locations cannot be accurately calculated.
Global – The Antarctic Minke Whale and Dwarf Minke Whales are found throughout the Southern Hemisphere from their mid-latitudes breeding grounds (30° S and 10° S) during the winter months then migrating deep in the Southern Ocean up to the Antarctic ice edge to feed over the summer months. The Antarctic Minke Whale is considered to be an oceanic whale preferring the deeper waters off the continental shelf.
Dwarf Minke Whales have been recorded in the waters off South Africa, Australia, New Zealand, New Caledonia and eastern coast of South America from March to December. Scattered sightings have been made in the sub-Antarctic from December to March.
Whaling data has indicated that mature males and females arrive at different times during the feeding season – males in June, females in July. Similarly sexual segregation has been observed in the breeding grounds with immature Antarctic Minke Whales comprised the larger proportion of the catch off Durban in South Africa, during the early part of the season between April to May (Best 1982). Data from Brazil (Williamson 1975) also suggests segregation by sexes (as well as by size) during the winter migration.
Distribution in the low latitudinal breeding grounds is predominately composed of solitary individuals that from into small pods of approximately five whales during Spring, then returning back to solitary individuals during November prior to heading south to the feeding grounds. Single individuals to small pods have been observed in the feeding grounds.
Population The International Whaling Commission (IWC) estimated the global population of Minke Whales in the Southern Hemisphere at 761 000 individuals (±5%). How reliable this number is is uncertain as the methodology of these surveys has recently been revised.
Currently there are no population estimates, nor any population trends available for Antarctic Minke Whales in Australian waters. It is thought that extreme population fluctuations within Australian waters are unlikely as there has been no whaling and that both their breeding and feeding grounds occur within Australian territory.
Minke whales gather in the Southern Ocean feeding grounds off Antarctic from November, peaking in January through to February. Timing of this gathering differs between the sexes and and age classes, with the majority of the mature population of Antarctic Minke Whales distributed south of 40° S during the summer (Gambell et al. 1975).
Tragically Antarctic Minke Whales have undergone extensive population reductions as they where the species targeted by Japanese ‘scientific’ whaling that continued until very recently. Whaling caused extensive population reductions with approximately 14 600 whales killed off the breeding grounds off Brazil, (Zerbini et al. 1997); 1113 off Durban in South Africa (Best 1982); and over 98 200 in the Antarctic feeding grounds between 1957 and 1987 (Horwood 1990). Japan reportedly took over 7000 Antarctic Minke Whales under IWC scientific research permits between 1987–2004. From 2005 the IWC allowed 850 ±10% Antarctic Minke Whales per annum to be killed.
The Ribbon Reefs, Great Barrier Reef, Qld
Habitat The Antarctic Minke Whale is considered to be an oceanic whale primarily found offshore within pelagic habitats (near the surface or in the open water) of the cold Antarctic waters between 21° S and 65° S. They prefer pelagic waters exceeding 600 m depth for breeding during the winter months. Over summer they will congregate along the sea ice edge to feed. They have also been been sighted well into the sea ice zone.
A 1996 survey of Australian Antarctic Territories found Antarctic Minke Whales unevenly distributed with more being found west of 120° E and concentrated south of the southern boundary of the Antarctic Circumpolar Current. They were found almost exclusively in a thin band of colder Antarctic Coastal Current water near the ice edge between 120° E and 150° E.
The Dwarf Minke Whales are famous for gathering within the Great Barrier Reef between Cains and Lizard Island on the Ribbon Reefs during June to July. Here they are known to approach boats and interact with people.
Behaviours Minke Whales are very active, highly manoeuvrable ittle whales that have been described as behaving more like Dolphins than whales. Know for their short high speed bursts and it thought they can dive to at least 140 metres in depth and for more than ten minutes. Surface activities include spyhopping and breaches. More unusual is when they occasionally swim on the surface for prolonged periods exposed from nose to fin, this has been called ‘motorboating’.
Antarctic Minke Whale tend to be more solitary usually only being seen by themselves or in pairs unless they’re feeding when they will gather in larger numbers.
Dwarf Minke’s are highly inquisitive shaking out interactions with boats and people. On the Great Barrier Reef they will gather around boats and swim up to people in the water.
Sounds – Minke are famous for making the ’Star Wars’ sounds.
Baleen whales produce sound differently to the toothed whales as they lack the system of air sacks, melon organ and sound-making ‘phonic lips’ in their forehead. So far there is no evidence that Minke whales can make the very high frequency sounds such as dolphins do for echolocation. It is thought that Minke whales therefore make the sounds using their larynx even though they lack vocal cords.
Dwarf Minke Whales produce sounds between 50–9400 Hz, which is well within the range of human hearing 18 Hz–20,000 Hz. People snorkelling in the water with them often report hearing the whales calls which sound like a mechanical sounding call that has three rapid pulses and a longer trailing note. They are also known to make almost pig like grunts, moans and belches. It is thought that these low frequency calls may be used to communicate with other whales as they can travel great distances underwater.
Whilst studying the calls of Dwarf Minke Whales Dr Jason Gedamke confirmed that it was the whales making the sounds. He also noted that the “star-wars” vocalisations shared similarities with the mating calls of other whale species such as Humpbacks, so this sound may only be made by the male whales.
Feeding Minke Whales migrate deep into the Southern Ocean too feast on Antarctic Krill (Euphausia superba) and other smaller krill species (E. spinifera and E. crystallorophias). It is thought that they will opportunistically feed on fish if the opportunity arises when migrating but for the main part don’t eat during migration and breeding.
Antarctic Krill are found near the surface in so it is thought that the whales do not need to dive very deeply to feed on them.
The distribution and feeding habits of newly weaned calves is unknown, but given that they are born in lower latitudes where Antarctic Krill are not readily available it is thought they feed on copepods, small euphausiids or fish.
Life Cycle The life history of Antarctic Minke Whale in Australian waters is extremely limited and many assumptions are based on data from South African and Brazilian populations.
Breeding occurs from June through December, with a peak between August and September. Gestation lasts about 10 months with calving occurring from late May to early June in warmer waters north of the Antarctic Convergence. No definite calving grounds are known although newborn calves have been seen from Victoria to southern Queensland (near Fraser Island and Lady Elliot Island) during April to June. Usually one calf of about 2 to 2.8 metres is born although twins and even triplets have been recored. Newborns grow about 1cm per day on the rich fatty milk and will be weaned after about five months and around 5.7 m in length. Antarctic Minke Whales will ovulate again about four months after calving, leading to a 14 month calving cycle. It is believed that the long mating season allows females continue to fall pregnant again and continue a rapid reproductive capacity within the population.
Like all whales Minke Whales are affected by ocean pollution, noise, climate change, ocean warming and acidification. Killer Whales are known predators of Minke Whales with one estimate suggesting that Antarctic Minke Whales comprise 85% of the diet of Killer Whales in the Southern Oceans (Stewart & Leatherwood 1985).
Threats Like all marine mammals Minke Whales have a number of natural and man made threats. Natural – predation by Killer Whales and sharks. Disease and old age. Man Made – Whaling, pollution, climate change, acoustic disturbance, ship strikes, entanglement and bycatch, over-harvesting of food sources such as Krill.
TheMinke Whale Project My sincere thanks to Dr Matt Curnock, Research Officer – Minke Whale Project, James Cook University for all his generous advice and guidance in creating this page.
References/Sources Australian Department of the Environment, Canberra QLD Department of the Environment Whales, Dolphins and Porpoises by Mark Carwardine Whales, Dolphins & Seals: A Field Guide to the Marine Mammals of the World by Hadoram Shirihai and Brett Jarrett
