Deep dive...into Minke whales

The minke whale is the second smallest member of the baleen family, growing to a maximum of 10 metres long and weighing up to nine tonnes.  

The scientific name for the Common minke species, Balaenoptera acutorostrata, translates to ‘sharp snouted winged whale’. And the name ‘minke’ comes from a Norwegian novice whaling spotter called Meincke, who is said to have mistaken a minke whale for a blue whale.  

The minke whale is also a member of the rorqual family of whales (these whales have baleen, a dorsal fin and throat pleats). Minke whales are usually quite solitary, spotted on their own or in small groups of two to three, although it is possible to see them in larger groups (usually when they are feeding).  

The species is recognisable from its slender and streamlined body, its baleen pleats that expand during feeding and its narrow, triangular rostrum (upper jaw) which is proportionally shorter than ones in other rorquals.  

Its colouring is black to grey on top with white below, with two areas of lighter grey on each side of the body – one behind the flippers and the second one around the tall dorsal fin.   

Minke whales are found in two distribution groups – one in the northern hemisphere and one in the southern. Each of the groups migrate to their respective polar regions to feed for several months of the year before returning to more temperate waters.

Northern hemisphere whales have a distinctive white band located in the middle of their flippers, while the southern variety doesn’t have this. And southern hemisphere minke whales tend to be slightly larger in size than the northern species and are referred to as Antarctic minke.  

There is an unofficial sub-species of the Common minke, called the dwarf minke whales. As you’d expect, it’s smaller in size.  

Dwarf minke whales grow to seven to eight metres long and weigh up to 6.3 tonnes. Their colouring is slightly different also with a bright white path on the upper part of their pectoral fin which extends up around the shoulders and back. They also have darker shading on their head compared to their bigger counterparts.  

The estimated life span of the minke whale is 50 years old. 

Minke whales are more difficult to spot in the water, compared to other whales, because they send out a small and weak blow from their two blow holes. They also surface from the water snout-first and don’t raise their flukes out of the water when they’re diving (they roll their back and body above the surface of the water before taking a deep dive).   

The overall effect is of a graceful creature gliding through the water and is a beautiful sight to behold.   

Minkes can stay submerged for up to 15 minutes before they need to come back up for air. They’re often spotted spy hopping, especially in icy areas, and they’re known to be curious creatures, with some individuals approaching vessels and swimming alongside them. Minkes are fast swimmers, capable of reaching speeds up to 30-38 kilometres per hour.  

Some interesting research has been carried out into the calls of minke whales. A study by the University of California, published in 2022, identified four key Antarctic minke whale calls.

The most common was the rumble, a short call lasting just over one-tenth of a second and said to sound like pulling up a zipper. The three others are named the growl, boom and the downsweep (this had been reported back in the 1970s but was mistakenly attributed to the common minke whale).

The study was also able to connect the calls to particular types of behaviour and times of day or night when they take place.

The species is found in oceans all over the world, in polar, temperate and tropical areas (though they’re not spotted frequently in the latter). 
 
They feed most often in the cooler waters at higher and lower latitudes, with some minke whales migrating long distances each year to warmer waters and some opting to remain closer to their feeding grounds.  
 
Research shows that older male minkes are more commonly found in the polar regions during the summer feeding season. Mature females also travel into these areas but are more likely to stick closer to coastal waters instead of the open ocean.  
 
Dwarf minke whales are found almost exclusively in the southern hemisphere, most frequently in areas off Australia, South America and South Africa.  

Whalers in the 19th and 20th centuries initially overlooked the minke whale as a target species as it was considered too small and too fast to be worth hunting. But when the larger species became severely depleted and tricky to locate, attention turned to the minke.  
 
Whaling practices have had an impact on population, particularly since whaling started to focus on them more in the late 1960s and 1970s onwards. But over the whole period of whaling, minke whale numbers have been less impacted when compared to other species such as the grey whale, blue whale or humpback whale.  
 
Some experts say the minke whale may have had some advantages in the early years of whaling as there was less competition for food as other whale species numbers reduced in numbers.  
 
Over the past 50 years though, the minke whale has been on the radar of countries that continue to commercially hunt and kill whales. Japan, Norway and Iceland target minkes as part of their catch (with quotas from the International Whaling Commission). In February 2022, Iceland indicated that its whaling would come to an end in 2024 as demand for whale meat has dwindled. 
 
Greenland has catch limits from the International Whaling Commission for aboriginal subsistence whaling, and they include minke whale in these catches.  
 
Estimates of the global minke whale population vary from 500,000 to 1 million. About three quarters of the species are located in the southern hemisphere, with the next biggest population group in the North Atlantic and after that, the north Pacific Ocean.  
 
Overall, the Common minke is designated as Least Concern on the IUCN Red List for Threatened Species. The Antarctic minke is listed as Near Threatened on the list.  

Minke whales are side lungers when it comes to feeding – they open wide and gulp in large amounts of sea water and food. Their baleen plates filter the prey from the water, which drains back out.  
 
Antarctic minke whales feed almost exclusively on krill while the Common minke eats a wider range of food (plankton, crustaceans, anchovies, dogfish, eels, herring, salmon, cod, mackerel and more). Common minkes off Greenland eat krill, like their Antarctic counterparts.  

Like other whales, minkes can become entangled in fishing gear which goes on to cause injury, fatigue, comprised feeding and sometimes even death.  

Minke whale bycatch has been observed to be particularly high off the coasts of Korea and Japan.

Minke whales are at risk of vessel strikes throughout their range but the threat is much higher in coastal areas with busy ship traffic. Trans-polar shipping routes are expected to become busier as Arctic sea ice continues to melt year-on-year.

This will have an impact on whales in terms of increased vessel strikes, increased noise and pollution.  

As discussed earlier in the article, whaling is still a threat for minkes as several countries continue to hunt and kill the species.

Climate change and pollution are a threat to all whales and dolphins because of the loss of habitat as waters become warmer. Minke whales are particularly vulnerable to the loss of ice in the polar regions, as it’s a vital feeding ground for the species.  
 
Plastics and micro plastics, along with chemical pollutants, entering into the water system are a serious threat to all creatures in our ocean.  
 
Minke whales, like other whales, use noise to communicate and to locate prey and increased noise pollution from vessels and other human activity interferes with this ability.  

Orca are the only known natural predator of minke whales. Attacks have been observed more frequently in the southern hemisphere.  

Check out this video of a curious minke whale in Portuguese waters: