Wet Beast Wednesday: bowhead whale
You know how some people just seem to excel at a ton of things at once for no particular reason? Yeah, this whale is kind of like that. It's a multiple record setter among whales but also mammals in general. Come learn about the wild biology of the bowhead whale.
(Image: a pair of bowhead whales swimming at the surface of the water, seen from above. They are large, gray, rotund whales with an unusual jawline. The upper law is very slender and the lower law is very large and curves up and down. They have paddle-like flipper and broad flukes. End ID)
The bowhead whale (Balaena mysticetus), also called the arctic whale, polar whale, or Greenland right whale (it's not a right whale but they are closely related) is one of the largest whales in the world, usually cited as the 2nd largest after the blue whale. They are fairly rotund whales with robust bodies and exceptionally large heads. The head makes up 40% of the whale's total lengths, the most of any whale. The rostrum (upper jaw) has a notable curve upwards, making the head almost triangular and giving the whale a strange, curved jawline. The name bowhead whale comes from the similarity of the rostrum to a ship's bow. Bowhead whales have the largest mouths of any animal and, as baleen whales, they have hundreds of sheets of comb-like baleen hanging from either side of the upper jaw. The baleen is the longest of any species. Bowheads have stout flukes and round, paddle-like flippers, with males generally having longer flippers than females. The body is mostly black or gray, but with a white chin and white spots on the tail and fluke, the latter of which usually develops later in life. Bowhead whales have no dorsal fin. Adults typically reach between 14 and 18 meters (46 - 59 ft) long and 7,500 to 10,000 kg (166,000 - 220,000 lbs), with females being slightly larger.
(Image: a bowhead whale facing to the right of the camera. Part of the white chin is visible from this angle. Its body is dark gray and it has several scars. The eye is located near the back of the jaw and is very small. End ID)
Bowhead whales live in the Arctic regions of the Atlantic and Pacific oceans and are the only whales who spend their entire lives in Arctic and subarctic waters. Their range has moved northward since records started being kept, which could be a reaction to warming oceans or whaling. To protect themselves from the cold, bowhead whales have the thickest blubber of any whale, up to 50 cm (19.7 in) thick in places. The shape of their heads and lack of dorsal fins let the whales specialize in swimming under pack ice. Dorsal fins risk getting caught on ice so the bowheads and other arctic species like narwhals and beluga lack them. The large head and its triangular shape allows the whale to smash its way through the ice to reach air. Bowheads migrate south for the winter, but never go so far south that they leave subarctic waters. Bowheads are less social than many other large whales. They tend to be solitary or swim in small pods of usually 2 or 3 members, but up to 10 when conditions are good. While often solitary, bowheads are highly vocal and appear to use whale song to communicate and socialize with each other over large distances. It could be said that bowheads aren't antisocial, they're just introverted and need their space. When they do congregate, they tend to show off through breaching and slapping the water with their tails.
(Image: a side view of a bowhead whale's head. The chin is very white and has a row of black dots running across it. End ID)
Belugas are predatory filter-feeders who target small crustaceans. The majority of their food comes in the form of krill, copepods, amphipods, and mysids, but small fish, jellies, squid, and other animals may be caught and eaten. Bowheads locate swarms of krill with echolocation and will swim through them while opening their mouths. This creates a vacuum that sucks water and prey into the mouth. The whale then closes its mouth and uses its tongue (which can get up to 5 meters/16.4 ft long) to force the water out through the baleen. The baleen acts like a sieve, trapping prey inn the mouth, where it is then swallowed. Bowheads need to eat around 2 tons of food a day to survive. Opening and closing their mouths takes so much energy that the whales won't do it unless they're sure they'll catch enough food to offset the energy costs with surplus. Bowheads usually feed at or near the surface. They can make dives up to 150 meters deep in rare occasions and can spend up to an hour underwater. They appear to use their long dive duration for distance rather than depth, allowing them to move long distances under pack ice.
(Image: a bowhead whale feeding at the surface of the water. It is turned on its side and its moth is open, exposing the plates of baleen, which look kind of like hair. End ID)
Bowhead mating season starts and peaks in March, but can last until August. The mating habits of the whales is understudied, but we do know that they sing unique songs during mating season, which are likely used to attract mates. Gestation takes 13 to 14 months and a single calf will be born that is up to 4.5 meters (15 ft) long and 1,000 kg (2,200 lbs). Newborn calves are very vulnerable and need to be born quick and then raised up to the surface by the mother so they can start breathing. Calves are born with a layer of blubber already established and they nurse on milk with a very high fat content to develop their blubber even further, allowing them to survive in frigid water. Calves usually wean after a year. Bowhead whales reach sexual maturity at 15 to 25 years, with females talking longer, and will reach their adult size at age 50 to 60. Females may remain fertile until well over 100 years old and males show no sighs of reproductive decline with age. The lifespan of bowhead whales is something of an open question, but genetic testing indicates that they can live for over 200 years, making them the longest-lived mammal by a considerable margin.
(Image: an overhead shot of a bowhead whale and its calf swimming at the surface of the water. the mother has notable white patches on its tail that the calf does not have. The calf is a smaller version of the mother. End ID)
The longevity of bowhead whales makes them an example of Peto's paradox. This relates to cancer rates. Cancer is primarily a disease of old age and occurs in cells. Whales like bowheads and blues, who live for a long time and have lots of cells, should in theory have a higher rate of cancer since they have a lot more chances for the bad luck to happen. However, whales actually have a lower cancer rate than humans. It has been hypothesized that large and long-lived animals face evolutionary pressure to develop better cancer-fighting mechanisms. Recent research has shown that Bowhead whales have an ability to repair their own DNA and proteins called CIRBP that can help keep mutations from happening. Research into these abilities could help with cancer prevention and treatment in humans.
(Image: a bowhead whale in the middle of breaching. Its head is out of the water and its chin is facing up. End ID)
Bowhead whales as a species are rated as least concern by the IUCN, but the population is subdivided into multiple stocks based on where they live that individually range from vulnerable to critically endangered. Bowheads were heavily targeted during whaling as their slow speed made them easy to catch and their size and thick blubber made them heavily profitable. Overhunting caused a major decrease in population and genetic diversity that the whales have still not recovered from. Even before commercial whaling, bowheads were hunted by the indigenous peoples of the Arctic circle for thousands of years. As whale hunts are culturally important to indigenous people in Canada, Alaska, Greenland, and Russia, subsistence hunting is permitted under regulations by the International Whaling Commission and the government of Canada. Bowhead whales are threatened by pollution, excessive noise from shipping, and global warming. The latter is especially concerning as it is leading to decreases in pack ice and the thick blubber of bowhead whales leaves them vulnerable to overheating. There are currently estimated to be 16,000 bowhead whales in the wild.
(Image: a bowhead whale spyhopping. It is positioned vertically with its head out of the water. End ID
