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Balaena mysticetus Linnaeus, 1758Bowhead Whale; Bowhead |
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PHYSICAL DESCRIPTION:
Found only in Arctic and sub-arctic waters, the bowhead whale has a massive body protected from the icy waters by a layer of
blubber
up to 2 feet thick. Its head is immense; it makes up nearly one-third of the bowhead's total body length. Its mouth can be as long as 16 feet (4.9 m), 12 feet (3.7 m) high, and 8 feet (2.4 m) wide and its tongue weighs about 1 ton (907 kg). In profile, a bowhead whale's head is triangular in shape, which may be an adaptation that enables the whale to break through the ice to breathe. Bowhead whales have a high bridge (termed the "stack") on which sit the nostrils, and with this are able to smash through ice that is 1-2 feet thick to breathe, presumably as they visually follow long cracks and valleys we now know to mark the bottom of the ice. There are 2 blowholes located at the highest point of the head that send 2 bushy, V-shaped blows 13 feet (4 m) in the air. While swimming, only the bowhead whale's triangular head and rounded back show above the surface of the water.
COLOR:
Bowhead whales are blue-black in color, except for a variable amount of white on the lower jaw. A series of irregular black spots are usually found on the white patch, and a few stiff hairs grow at the front of both the upper and lower jaws. In addition, there may be some white markings on the belly, and a gray-to-white band just forward of the fluke (tail). This "penduncle patch" near the tail turns whiter and larger with age, and very old bowhead whales may have all-white tails.
FINS AND FLUKE:
The bowhead whale's broad back has no dorsal fin, a characteristic of the genus. The deeply-notched flukes of a mature bowhead whale can measure 25 feet (7.6 m) from tip to tip. Flippers are broad and paddle shaped, about 6 feet (1.8 m) in length.
Length and Weight:
Adult males reach physical maturity at 50 feet (15 m) and may weigh in excess of 60 tons (54,431 kg). Sexual maturity is reached at 38 feet (11.6 m). Adult females are slightly larger than males at both physical and sexual maturity. Maximum length exceeds 60 feet (18.3 m).
Feeding:
Bowhead whales feed on planktonic organisms including copepods, amphipods, euphausiids, and various other crustaceans. They consume about 2 tons (1800 kg) of food each day. As a
baleen
whale, it has a series 325-360 fringed overlapping plates of
baleen
hanging from each side of the upper jaw, just outside where teeth might otherwise be located. These plates consist of a fingernail-like material called keratin that frays out into fine hairs on the ends inside the mouth near the tongue. The plates are dark gray-to-black and are the longest baleen of any whale, measuring up to 14 feet (4.3 m) in length and 12 inches (30 cm) in width. While feeding, a bowhead whale skims through the water with its mouth open. As water flows into the mouth and through the baleen, prey are trapped on the inside near the tongue to be swallowed.
Mating and Breeding:
Mating takes place in late spring or early summer, and the calves are 11-18 feet (3.5-5.5 m) long at birth. Calving is every 3 to 4, but occasionally with intervals as long as 7 years. Gestation length has not been confirmed but is probably 13 to 14 months, potentially longer. Calves are born with a thick layer of blubber which helps them survive in freezing water immediately after birth. The calf nurses for about 9 to 12 months.
Distribution and Migration:
Migration is seasonal, and movements are determined by retreating or advancing ice. Always close to the edge of the Arctic icepack, bowhead whales of the Chukchi-Beaufort-Bering Sea follow it south to the Bering Sea in winter northeast to the Beaufort Sea, and northwest to the Chukchi Sea. They feed in the Arctic Ocean in summer. On the northward migration, bowhead whales are often accompanied by beluga whales, who follow them through the leads in the ice. Segregation by age and sex is evident during certain phases of the migration. Worldwide, bowhead whales are found in the western Arctic (Bering, Chukchi, and Beaufort Seas), the Canadian Arctic (Baffin Bay, Davis Strait, and Hudson Bay), the Okhotsk Sea (in Russia, between the mainland, the Kamchatka Peninsula, and the Kuril Islands), and Spitsbergen westward to Greenland in the far north Atlantic Ocean. The Spitsbergen stock may be extinct.
Natural History:
Bowhead whales usually travel alone or in small groups of up to 6 animals. Larger congregations may be seen in the feeding grounds. These whales are slow swimmers, and will retreat under the ice when they are alarmed. Their sight and hearing are excellent, and they vocalize with low moans that at times occur in discrete sequences of sound representing simple song. These may be mating displays, but this has not been investigated. Their only known predator, besides man, is the killer whale. There is increasingly good evidence that bowhead whales can live for well over 100 years, and they may be the longest-lived mammal on Earth.
Status:
Commercial whalers discovered the bowhead whale as early as 1611 in the eastern Arctic and in 1848 in the western Arctic. Unregulated commercial whaling continued into the early 1900s, reducing the bowhead whale populations to the point of extinction. Bowhead whales have been completely protected from commercial whaling since 1946; Eskimos have hunted "the whale" for centuries. In accordance with
International Whaling Commission (IWC)
rules, Eskimos are legally allowed to hunt an allocated number of bowhead whales each year for food and oil.
Hundreds of bowhead whales were taken each year in the late l800s and early 1900s, and great profits were made from the sale of oil and baleen. A single bowhead whale could yield up to 100 barrels of oil and 1500 pounds of baleen or "whale bone." In 1859 the price of whale oil dropped dramatically because of substitutes made from petroleum then discovered in western Pennsylvania. Hunting continued for the baleen alone and the rest of the animal was discarded. Baleen was used for such things as corset stays, buggy whips, watch springs, skirt hoops, fishing rods, and umbrella ribs. The use of baleen became unnecessary in the early 1900's as a result of the development of spring steel. At present, the number of bowhead whales of the Chukchi-Beaufort-Bering Sea is estimated to exceed 8,000, those of the eastern Canadian Arctic and of the Okhostsk Sea in far east Russia are in the hundreds.
Bibliography:
Acknowledgements:
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Home
Balaena mysticetus
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By James Justice
Bowhead whales ( Balaena mysticetus ) once inhabited oceans throughout the northern hemisphere. Over the last hundred years the population of bowhead whales has been greatly reduced into five geographically secluded stocks. These stocks are: the Spitsbergen stock, which inhabit the north Atlantic; the Davis Strait and Hudson Bay stocks, which both inhabit the west-northern Atlantic; the Okhotsk stock, which are found in the Okhotsk Sea; and Bering Sea stock, found in the area of the Bering Sea (Shelden and Rugh 1995). Bowhead whales inhabit the Arctic Ocean and associated seas. They are rarely found below 45 degrees north latitude (Nowak 1999). ( Nowak, 1999 ; Shelden and Rugh, 1995 )
Biogeographic Regions:
arctic ocean
(
native
);
atlantic ocean
(
native
);
pacific ocean
(
native
).
Balaena mysticetus lives in the colder waters of the northern hemisphere. Of the current total population, approximately 700 are found in the north Atlantic while 7,000 are located in the north Pacific. Balaena mysticetus usually follow the receding ice drifts (Shelden and Rugh 1995). During summer they can be found in bays, straits, and estuaries (Nowak 1999). ( Nowak, 1999 ; Shelden and Rugh, 1995 )
These animals are found in the following types of habitat:
polar
;
saltwater or marine
.
Aquatic Biomes:
coastal
.
Balaena mysticetus is the second largest whale in the world, second only to the blue whale ( Balaenoptera musculus ) . The name "bowhead" comes from their bow-shaped mouth. The lower jaw makes a U-shape around the upper jaw. This lower jaw is usually marked with white spots, contrasting with the rest of the whale's black body (Nowak 1999). Baleen in the bowhead whale's mouth is the largest of any cetacean with 300 baleen plates measuring 300-450 centimeters in vertical length. The skull makes up almost one-third of the total body length, is curved and asymetric (Lanier 1998). Bowhead whales, on average, are sixty feet in length and weigh around 100 tons. Contributing to the whale's mass is a two foot thick layer of insulating blubber (Nicklen 2000). Balaena mysticetus also has a small pectoral fin for its size, less than 200 centimeters in length (Nowak 1999). Bowhead whale females measure between 16 and 18 meters in length, males measure between 14 and 17 meters in length. Bowhead whales weigh from 75,000 to 100,000 kg. ( Lanier, 1998 ; Nicklen, 2000 ; Nowak, 1999 )
Some key physical features:
endothermic
; homoiothermic;
bilateral symmetry
.
Sexual dimorphism:
female larger.
Males attract female B. mysticetus through songs. It is unknown how long these pair bonds last or how many matings male bowhead whales take part in during mating season.
Mating in Balaena mysticetus usually occurs during late winter and early spring. Spring migration takes place soon after this and the female gives birth between April and June, with most births occurring in May. It takes twenty years for a Bowhead whale calf to reach sexual maturity. At this time, they can be between 12.3 and 14.2 m in length (Shelden and Rugh 1995). Females usually reach sexual maturity before males and are also 1 to 2 meters larger than males at this time (George et al. 1999). In some cases pseudohermaphroditism can occur, leaving a whale to appear female, but also having male sex organs (Shelden and Rugh 1995). ( George et al., 1999 ; Shelden and Rugh, 1995 )
Key reproductive features:
iteroparous
;
seasonal breeding
; gonochoric/gonochoristic/dioecious (sexes separate);
sexual
;
viviparous
.
When a calf is born, its average length is 4.25 to 5.25 m. Calves grow approximately 1.5 cm a day. The calf is fed with its mother's milk until it is weaned, which occurs between nine and fifteen months after birth. After weaning, growth rate decreases. After births occur, whales segregate into groups in order to migrate. Calves and mothers are in the front group. Perhaps this is to allow them to be the first to feed on food aggregations that are encountered. For the most part it seems that females take care of the young, although there have been some cases of Balaena mysticetus travelling in groups of three: a mature male, a mature female, and a calf (Shelden and Rugh 1995). ( Shelden and Rugh, 1995 )
Parental investment:
precocial
; pre-fertilization (provisioning, protecting: female); pre-hatching/birth (provisioning: female, protecting: female); pre-weaning/fledging (provisioning: female, protecting: female); pre-independence (protecting: female).
Balaena mysticetus has a remarkable lifespan. The average age of animals captured during whaling is estimated at 60 to 70 years old, based on examination of changes in the nucleus of the eye over time. However, several individuals have been discovered with ancient ivory and stone harpoon heads in their flesh and examination of their eye nucleus has resulted in estimated lifespans up to 200 years (George et al. 1999), making bowhead whales the longest lived mammalian species. There is little knowlege of diseases in B. mysticetus that would effect the average lifespan (Stover 2001). ( George et al., 1999 ; Stover, 2001 )
When migrating, bowhead whales divide into three smaller groups in which to migrate during the spring and fall. The groups they segregate into are: subadults, intermediate mature whales, and large adults. Each of the five stocks show distinct migration patterns dependent on the supply of food and the extension or recession of the polar ice cap (Shelden and Rugh 1995). ( Shelden and Rugh, 1995 )
Key behaviors:
natatorial
;
motile
;
migratory
;
social
.
Balaena mysticetus is a baleen whale, which means that they filter water through baleen plates, feeding on the organisms caught in the plates and pushing the rest of the water out. Balaena mysticetus can sometimes feed opportunistically during the spring migration, but mostly feed during the winter months on their feeding grounds. They eat crustacean zooplankton, epibenthic organisms, and some benthic organisms. Crustacean zooplankton, such as copepods, are not important food sources for young B. mysticetus , but increase in importance with age (Shelden and Rugh 1995). Copepods are small crustaceans, which a bowhead whale can filter at approximately 50,000 per minute (Stover 2001). Balaena mysticetus sometimes form groups of up to fourteen individuals, in which they make a V-shape formation. In this formation they travel at the same speed and filter feed together (Nowak 1999).
Foods commonly eaten include: euphausiids, copepods, mysids, gammarid amphipods, other benthic organisms ( Nowak, 1999 ; Shelden and Rugh, 1995 ; Stover, 2001 )
Primary Diet:
carnivore
(eats non-insect arthropods);
planktivore
.
Animal Foods:
aquatic crustaceans;
zooplankton
.
Foraging Behaviors:
filter-feeding
.
Bowhead whales are protected from predators by their large size. They are also known to take shelter under ice drifts. As the oceanic waters of the polar regions become frozen, bowhead whales will swim beneath the extending polar ice cap. In order to survive under the ice cap, B. mysticetus can break through the ice in order to breathe without making themselves accessible to other marine predators (Stover 2001). In a study in 1995, it was found that one-third of the animals of the Davis Strait stock showed scars from killer whale attacks (Shelden and Rugh 1995). ( Shelden and Rugh, 1995 ; Stover, 2001 )
Barnacles use B. mysticetus as both a mode of transportation and a way to encounter fresh food supplies (Lanier 1998). Bowhead whales play an important role as predators of plankton in the arctic ocean. ( Lanier, 1998 )
The only way in which Balaena mysticetus may interfere with humans is in marine fishing. The large bowhead whale has been known to collide with sailing vessels on rare occassions as well as get caught in nets fishing for other oceanic life (Shelden and Rugh 1995). ( Shelden and Rugh, 1995 )
Balaena mysticetus is a benefit to the whaling industry. Because of their large size, one whale can bring a large bounty of whale meat, massive baleen, and the blubber for which it is primarily hunted. In fact, B. mysticetus is the most economically valuable of all cetaceans (Nowak 1999). Many native people such as Eskimos also depend on these resources for the survival of their communities economically by using baleen for tools, blubber for fuel, and whale meat for food and trade (Nicklen 1995). ( Nicklen, 2000 ; Nowak, 1999 )
Ways that people benefit from these animals:
food
; body parts are source of valuable material;
ecotourism
; research and education.
IUCN Red List:
[link]
:
Lower Risk - Conservation Dependent.
US Migratory Bird Act:
[link]
:
No special status.
US Federal List:
[link]
:
Endangered.
CITES:
[link]
:
Appendix I.
Primary conservation efforts for Balaena mysticetus involve reducing or ending the hunting of this species. Agencies who are playing parts in the conservation of the species are the Alaskan Eskimo Whaling Commission (AEWC) and the National Oceanic and Atmospheric Administration (NOAA) (Shelden and Rugh 1995). Native people have been allowed to take only one whale every two years (Nicklen 2000). Whale populations plummeted as a result of a huge expansion in the whaling industry from the 1600s to the early 1900s (Shelden and Rugh 1995). ( Nicklen, 2000 ; Shelden and Rugh, 1995 )
Find Balaena mysticetus information at
James Justice (author), University of Northern Iowa.
Jim Demastes (editor), University of Northern Iowa.
To cite this page: Justice, J. 2002. "Balaena mysticetus" (On-line), Animal Diversity Web. Accessed February 09, 2010 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Balaena_mysticetus.html.
Disclaimer: The Animal Diversity Web is an educational resource written largely by and for college students . ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.
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