Bowhead whale
Bowhead whale in other languages
| Latin | Balaena mysticetus |
| Norwegian | Grønlandshval |
| German | Grönlandwal |
| French | Baleine du Groenland |
Bowheads are dark grey on the back and lighter on the belly. They have elevated nostrils and no dorsal fin. Females are slightly larger than males; their lengths are 16–18 m whereas males are 14–17 m. Bowhead whales weigh 75,000–100,000 kg. The bowed appearance of their mouth gives them their name. Their blow is V-shaped.
Distribution
The bowhead is the only full-time arctic resident among the baleen whales. It is a species that lives in close association with ice on a year-round basis and it has a patchy circumpolar distribution that varies seasonally as the ice extent contracts and expands. Bowhead whales usually remain close to the southern boundary of winter ice; as the ice cover recedes the whales move northwards and disperse in pack ice areas during spring, summer and autumn.
There are five defined stocks of bowhead whales in the Arctic. One is the Spitsbergen stock, which is confined to the north-east Atlantic where they have been observed from the Greenland Sea between Greenland and Svalbard, eastward past the Barents and Kara Seas, well into the Russian Arctic.
Ecology
Bowheads number in the thousands in the Alaskan stock, but the other bowhead stocks only include hundreds or tens of animals.
In Svalbard sightings of this species are rare. No estimate is available, but it is known that the population is very small.
The bowhead’s adaptations to living in the Arctic are extensive. It has the greatest development of the blubber layer seen among whales (up to 30 cm thick), and it has complex blood circulatory mechanisms for conserving heat. Their raised nostrils and lack of dorsal fin are thought to be adaptations to living in ice. The bowhead is a very slow swimmer compared to the more stream-lined baleen whales.
Bowheads also have extreme development of baleen (reaching lengths of four to five metres), which is a series of filtering plates that hang in the mouth from the top jaw. The feeding plates of this and other baleen whales are adapted to filter small prey out of large volumes of water. The muscular tongue helps clear the prey off of the hairy inside surface of the plates and helps to direct food into the throat.
Bowheads are assumed to obtain most of the food necessary for annual growth and maintenance, during the summer months, although some feeding almost certainly takes place outside the summering areas. They feed throughout the water column, skimming the surface, but also feeding near the sea floor.
Bowhead whales have a remarkable vocal repertoire, which they use frequently, suggesting that sound serves an important function in their lives. It is thought that bowheads communicate acoustically with one another over very long distances.
Similar to many other cetaceans, bowhead whales show some sex and age segregation. Mothers and calves migrate independently of male groups and often feed in different areas as well during the summer months. This species appears to be “loosely social”, travelling in very small groups most of the time and without long-term associations outside the mother–calf pair between individual animals. It has been suggested that there is coordination among activities of individuals separated by considerable distances, so longdistance communication of some sort might be taking place.
Bowheads feed mainly on planktonic crustaceans, including copepods and euphausiids (ranging in size from three to 30 mm), although they will also take small schooling fishes such as polar cod in addition. Killer whales are the only known natural predator.
Life history and reproduction
Bowhead whales are the only baleen whale species that gives birth to their calves in arctic waters. In the Canadian Arctic they mate and calve during their northward spring migration and spend the summer feeding and raising their young. Mating groups often consist of a female and several males, similar to right whales.
A lot of boisterous activities take place during mating, such as breaching and fluke slapping, but it is not clear whether most of this is competitive or whether some form of cooperation takes place among males during mating.
Gestation lasts 13–14 months, after which the single calf is born. Calves remain with their mothers during the summer and subsequent autumn migration and probably through the winter as well.
This species has a long inter-calving interval of about four years. Bowheads have a much delayed age at first reproduction. They do not commence breeding before they are approximately 25 years old.
They grow slowly, reaching final body size when they are between 40 and 50 years old and are thought to live to ages in excess of 200 years.
Management status and monitoring
Peoples of the North have hunted bowheads along their migratory routes for centuries. They were also the first Arctic whale species to be harvested intensively by commercial whalers. Because they are slow swimmers, and because they are so fat that they float when killed, early whalers that were operating out of small man-driven boats working off sailing ships targeted them. The Spitsbergen stock was the first to receive the attention of these early whalers and this species was the first of the Great Whales to be severely depleted. During intensive hunting that took place primarily from the 17th century up into the 19th century, bowheads were driven to near extinction throughout their range.
Some recovery has taken place in Alaska, where there is currently an aboriginal harvest that works within a quota system. Hunting of a bowhead or two has been permitted in recent years in the Canadian Arctic, on the basis of maintenance of cultural heritage.
All bowhead stocks are classified as endangered. Bowheads are protected in Svalbard.