The
bowhead whale (
Balaena mysticetus) is a species of the family
Balaenidae, in
suborder Mysticeti, and
genus Balaena, which once included the
right whale.
A stocky dark-colored whale without a
dorsal fin,
it can grow 14 to 18 m (46 to 59 ft) in length. This thick-bodied
species can weigh from 75 to 100 tonnes (74 to 98 long tons; 83 to 110
short tons).
[3] They live entirely in fertile
Arctic
and sub-Arctic waters, unlike other whales that migrate to low latitude
waters to feed or reproduce. The bowhead was also known as the
Greenland right whale or
Arctic whale. American whalemen called them the
steeple-top,
polar whale,
[4] or
Russia or
Russian whale. The bowhead has the largest mouth of any animal.
[5]
The bowhead was an early
whaling target. The population was severely reduced before a 1966
moratorium
was passed to protect the species. Of the five stocks of bowhead
populations, three are listed as "endangered", one as "vulnerable", and
one as "lower risk, conservation dependent" according to the
IUCN Red List.
[6]
Taxonomy
Carl Linnaeus first described this whale in the 10th edition of his
Systema Naturae (1758).
[7] Seemingly identical to its cousins in the
North Atlantic,
North Pacific and
Southern Oceans, they were all thought to be a single species, collectively known as the "right whale", and given the
binomial name Balaena mysticetus.
Today, the bowhead whale occupies a
monotypic genus, separate from the
right whales, as was proposed by the work of
John Edward Gray in 1821.
[8] For the next 180 years, the family Balaenidae was the subject of great
taxonometric
debate. Authorities have repeatedly recategorized the three populations
of right whale plus the bowhead whale, as one, two, three or four
species, either in a single genus or in two separate genera. Eventually,
it was recognized that bowheads and right whales were in fact
different, but there was still no strong consensus as to whether they
shared a single genus or two. As recently as 1998, Dale Rice, in his
comprehensive and otherwise authoritative classification,
Marine mammals of the world: systematics and distribution, listed just two species:
B. glacialis (the right whales) and
B. mysticetus (the bowheads).
[9]
Studies in the 2000s finally provided clear evidence that the
three living right whale species do comprise a
phylogenetic lineage,
distinct from the bowhead, and that the bowhead and the right whales are rightly classified into two separate genera.
[10] The right whales were thus confirmed to be in a separate genus,
Eubalaena. The relationship is shown in the
cladogram below:
| Family Balaenidae |
|
|
| The bowhead whale, genus Balaena, in the family Balaenidae (extant taxa only)[11] |
Balaena prisca, one of the five
Balaena fossils from the late
Miocene (~10
Mya) to early
Pleistocene (~1.5 Mya), may be the same as the modern bowhead whale. The earlier fossil record shows no related cetacean after
Morenocetus, found in a
South American deposit dating back 23 million years.
An unknown species of right whale, the so-called "Swedenborg whale" which was proposed by
Emanuel Swedenborg
in the 18th century, was once thought to be a North Atlantic right
whale by scientific consensus. However based on later DNA analysis those
fossil bones claimed to be from "Swedenborg whales" were confirmed to
be from bowhead whales.
[12]
Description
Skeleton of a bowhead whale
The bowhead whale has a large, robust, dark-colored body and a white chin/lower jaw. The whale has a massive triangular
skull, which the whale uses to break through the
Arctic ice to breathe.
Inuit hunters have reported bowheads surfacing through 60 cm (24 in) of ice.
[13] The bowhead also has a strongly bowed lower jaw and a narrow upper jaw. Its
baleen
is the longest of that of any whale, at 3 m (9.8 ft), and is used to
strain tiny prey from the water. The bowhead whale has paired blowholes,
at the highest point of the head, which can spout a blow 6.1 m (20 ft)
high. The whale's
blubber is the thickest of that of any animal, with a maximum of 43–50 cm (17–20 in).
[14] Unlike most cetaceans, the bowhead does not have a
dorsal fin.
[15]
Bowhead whales are comparable in size to the three species of
right whales. According to whaling captain
William Scoresby
Jr., the longest bowhead he measured was 17.7 m (58 ft) long, while the
longest measurement he had ever heard of was of a 20.4 m (67 ft) whale
caught at
Godhavn, Greenland, in early 1813. He also spoke of one, caught near
Spitsbergen around 1800, that was allegedly nearly 21.3 m (70 ft) long.
[16] In 1850, an American vessel claimed to have caught a 24.54 m (80.5 ft) individual in the Western Arctic.
[17]
It is questionable whether these lengths were actually measured. The
longest reliably measured were a male of 16.2 m (53 ft) and a female of
18 m (59 ft), both landed by natives in Alaska.
[18] On average, female bowheads are larger than males.
Analysis of hundreds of DNA samples from living whales and from
baleen
used in vessels, toys, and housing material has shown that Arctic
bowhead whales have lost a significant portion of their genetic
diversity in the past 500 years. Bowheads originally crossed ice-covered
inlets and straits to exchange genes between Atlantic and Pacific
populations. This conclusion was derived from analyzing maternal lineage
using
mitochondrial DNA. Whaling and climatic cooling during the
Little Ice Age,
from the 16th century to the 19th, is supposed to have reduced the
whales’ summer habitats, which explains the loss of genetic diversity.
[19]
A 2013 discovery has elucidated the function of the bowhead's large palatal
retial organ. The bulbous ridge of highly vascularized tissue, the
corpus cavernosum maxillaris,
extends along the center of the hard plate, forming two large lobes at
the rostral palate. The tissue is histologically similar to that of the
corpus cavernosum of the mammalian
penis.
It is hypothesized that this organ provides a mechanism of cooling for
the whale (which is normally protected from the cold Arctic waters by
40 cm (16 in) or more of fat). During physical exertion, the whale must
cool itself to prevent
hyperthermia
(and ultimately brain damage). It is now believed that this organ
becomes engorged with blood, causing the whale to open its mouth to
allow cold seawater to flow over the organ, thus cooling the blood.
[20]
Behavior
Breaching off Alaskan coast
Swimming
Bowhead whales are not social animals, typically traveling alone or
in small pods of up to 6. They are able to dive and remain submerged
underwater for up to an hour. However, the time spent underwater in a
single dive is usually limited to 9–18 minutes.
[13]
Bowheads are not thought to be deep divers but they can reach a depth
of up to 500 ft (150 m). These whales are slow swimmers, normally
traveling at about 2–5 km/h (1.2–3.1 mph).
[21]
When fleeing from danger, they can travel at a speed of 10 km/h
(6.2 mph). During periods of feeding, the average swim speed is reduced
to 1.1–2.5 m/s (3.6–8.2 ft/s).
[22]
Feeding
The head of the bowhead whale comprises a third of its body length, creating an enormous feeding apparatus.
[22] Bowhead whales are
filter feeders, feeding by swimming forward with mouth wide open.
[13] The whale has hundreds of overlapping
baleen plates consisting of
keratin
hanging from each side of the upper jaw. The mouth has a large
upturning lip on the lower jaw that helps to reinforce and hold the
baleen plates within the mouth. This also prevents buckling or breakage
of the plates from the pressure of the water passing through them as the
whale advances. To feed, water is filtered through the fine hairs of
keratin of the baleen plates, trapping the prey inside near the tongue
where it is then swallowed.
[23] The diet consists of mostly
zooplankton which includes
copepods,
amphipods, and many other
crustaceans.
[22] Approximately 2 short tons (1.8 long tons; 1.8 t) of food is consumed each day.
[23] While foraging, bowheads are solitary or occur in groups of two to ten or more.
[14]
Vocalization
Bowhead whales are highly vocal
[24]
and use low frequency (<1000 Hz) sounds to communicate while
traveling, feeding, and socializing. Intense calls for communication and
navigation are produced especially during migration season. During
breeding season, bowheads make long, complex, variable songs for mating
calls.
[21]
Reproduction
Sexual activity occurs between pairs and in boisterous groups of
several males and one or two females. Breeding season is observed from
March through August; conception is believed to occur primarily in March
when song activity is at its highest.
[21] Reproduction can begin when a whale is 10 to 15 years old. The
gestation period is 13–14 months with females producing a calf once every three to four years.
[18] Lactation typically lasts about a year. To survive in the cold water immediately after birth, calves are born with a thick layer of
blubber.
Within 30 minutes of birth, bowhead calves are able to swim on their
own. A newborn calf is typically 4–4.5 m (13–15 ft) long, weighs
approximately 1,000 kg (2,200 lb), and grows to 8.2 m (27 ft) within the
first year.
[18]
Health
Lifespan
Bowhead whales are known to be among the
longest-living mammals, living for over 200 years.
[25] In May 2007, a 15 m (49 ft) specimen caught off the
Alaskan
coast was discovered with the 3.5 in (89 mm) head of an explosive
harpoon of a model manufactured between 1879 and 1885. The harpoon was
probably manufactured in
New Bedford,
Massachusetts,
a major whaling center at the time, and experts estimated that the
wound was inflicted around 1890. According to one analysis, the whale
was probably harpooned sometime between 1885 and 1895. The whale's age
at the time of death was estimated at between 115 and 130 years.
[26][27][28][29][30]
Spurred by this discovery, scientists measured the ages of other
bowhead whales; one specimen was estimated to be 211 years old.
[31] Other bowhead whales were estimated to be between 135 and 172 years old. This discovery showed the
longevity of the bowhead whale is much greater than originally thought.
Genetic causes
It was previously believed the more cells present in an organism, the greater the chances of
mutations that cause age related diseases and
cancer.
[32]
Although the bowhead whale has thousands of times more cells than other
mammals, the whale has a much higher resistance to cancer and aging. In
2015, scientists from the US and UK were able to successfully map the
whale's
genome.
[33] Through comparative analysis, two
alleles
that could be responsible for the whale's longevity were identified.
These two specific gene mutations linked to the bowhead whale's ability
to live longer are the
ERCC1 gene and the proliferating cell nuclear antigen (
PCNA) gene.
ERCC1 is linked to
DNA repair as well as increased cancer resistance.
PCNA
is also important in DNA repair. These mutations enable bowhead whales
to better repair DNA damage, allowing for greater resistance to cancer.
[32] The whale's genome may also reveal physiological adaptations such as having low metabolic rates compared to other mammals.
[34] Changes in the gene
UCP1, a gene involved in
thermoregulation, can explain differences in the metabolic rates in cells.
Ecology
Drawing of an adult in 1884
Range and habitat
The bowhead whale is the only
baleen whale to spend its entire life in the
Arctic and sub-Arctic waters.
[35] The
Alaskan population spends the winter months in the southwestern
Bering Sea. The group migrates northward in the spring, following openings in the ice, into the
Chukchi and
Beaufort seas.
[36] It has been confirmed the whale's range varies depending on climate changes and on the forming/melting of ice.
[37]
Historical range could have been broader and more southern than that
of currently regarded as bowheads had been abundant among Labrador and
Newfoundland (
Strait of Belle Isle), and northern
Gulf of St. Lawrence at least until 16th and 17th century although it is unclear this was whether or not due to colder climate of those periods.
[38] Distributions of
Balaena during Pleistocene were far more southerly as fossils have been excavated from
Italy and
North Carolina, and thus could have overlapped between those of
Eubalaena based on locations where fossils have been excavated.
[39]
Population
It
is generally recognized that there are five stocks of Bowhead Whales.
These include: 1) the Western Arctic stock in the Bering, Chukchi and
Beaufort Seas, 2) the Hudson Bay and Foxe Basin stock, 3) the Baffin Bay
and Davis Strait stock, 4) the Sea of Okhotsk stock, and 5) the
Svalbard-Barents Sea stock. However, recent evidence suggests that the
Hudson Bay and Foxe Basin stock, and the Baffin Bay and Davis Strait
stock should be considered one stock based on genetics and movements of
tagged whales.
[40]
Western Arctic
The
Western Arctic Bowhead population, also known as the
Bering-Chukchi-Beaufort population, has recovered since the commercial
harvest of this stock ceased. A 2011 study estimated that the Western
Arctic Bowhead population was 16,892 (95% CI: 15,074-18,928), more than
triple the population estimate in 1978.
[41]
This study puts the yearly growth rate at 3.7% (95% CI = 2.8-4.7%) from
1978 to 2011. This data suggests that the Western Arctic Bowhead stock
may be at or near its pre-commercial whaling level.
[40]
Alaskan Natives continue to hunt small numbers of Bowhead Whales for
subsistence purposes. The Alaska Eskimo Whaling Commission, an Alaska
Native organization that manages the Bowhead subsistence harvest under a
cooperative agreement with the National Oceanic and Atmospheric
Administration, sets the harvest quota for each whaling village. The
Alaskan villages that participate in the Bowhead subsistence harvest
include: Barrow, Point Hope, Gambell, Savoonga, Wainwright, Kivilina,
Nuiqsut, Kaktovik, Wales, and little Diomede.
[42]
The annual subsistence harvest of the Western Arctic stock has ranged
from 14 to 72, amounting to an estimated 0.1-0.5% of the population.
[40]
Baffin Bay and Davis Strait
In
March 2008, Canada's Department of Fisheries and Oceans stated the
previous estimates in the eastern Arctic had under-counted, with a new
estimate of 14,400 animals (range 4,800–43,000).
[43]
These larger numbers correspond to prewhaling estimates, indicating the
population has fully recovered. However, if climate change
substantially shrinks sea ice, these whales could be threatened by
increased shipping traffic.
[44]
The status of other populations is less well known. There were about 1,200 off West Greenland in 2006, while the
Svalbard population may only number in the tens. However, the numbers have been increasing in recent years.
[45]
Hudson Bay and Foxe Basin
Sighting locations by researchers and hunters
Hudson Bay –
Foxe Basin population is distinct from the
Baffin Bay –
Davis Strait group.
[46]
Original population size of this local group is unclear, but possibly
around 500 to 600 whales annually summered in the northwestern part of
the bay in 1860s.
[47] Likely, the number of whales actually inhabit within Hudson Bay is much smaller than the total population size of this group,
[48]
and despite current population size is rather unclear, reports from
local indigenous people indicate this population is at least increasing
over decades.
[49]
Larger portions of usages of the bay is considered to be summering
while wintering is on smaller scale where some animals winter in
Hudson Strait most notably north of
Igloolik Island and northeastern Hudson Bay. Distribution patterns of whales in this regions are largely affected by presences of
killer whales
and bowheads can disappear from normal ranges due to recent changes in
killer whales' occurrences within the bay possibly because of changes in
movements of ice floes by
changing climate.
[49] Whaling grounds in 19th century covered from
Marble Island to
Roes Welcome Sound and to
Lyon Inlet and
Fisher Strait, and whales still migrate through most of these areas.
Mostly, distributions within Hudson Bay is restricted in northwestern part
[46] along with
Wager Bay,
[50] Repulse Bay,
[51] Southampton Island (one of two main know summering areas),
[52][51] Frozen Strait, northern Foxe Basin, and north of
Igloolik in summer,
[49] and satellite tracking
[53] indicates that some portions of the group within the bay do not venture further south than such as
Whave Cove[51] and areas south of
Coasts and
Mansel Islands.
[citation needed]
Cow – calf pairs and juveniles up to 13.5 m (44 ft) in length consist
of majority of summering aggregation in northern Foxe Basin while
matured males and non-calving females may utilize northwestern part of
Hudson Bay.
[49] Fewer whales also migrate to west coast of Hudson Bay,
Mansel and
Ottawa Islands.
[49] Bowhead ranges within Hudson Bay are usually considered not to cover southern parts,
[48][54] but at least some whales migrate into further south such as at
Sanikiluaq[citation needed] and
Churchill river mouth.
[55][56][57]
Congregation within Foxe Basin occurs in a well-defined area at 3,700 km (2,300 mi) north of Igloolik Island to
Fury and Hecla Strait and
Jens Munk Island and
Gifford Fiord, and into
Gulf of Boothia and
Prince Regent Inlet. Northward migrating along western Foxe Basin to eastern side of the basin also occurs in spring seasons.
[49]
Sea of Okhotsk
Not much is known about the endangered
Sea of Okhotsk population. To learn more about the population, these mammals have been regularly observed near the
Shantar Islands, very close to the shore, such as at
Ongachan Bay.
[59][60] Several companies provide
whale watching
services which are mostly land-based. According to Russian scientists,
this total population likely does not exceed 400 animals.
[58] Scientific research on this population was seldom done before 2009, when researchers studying
belugas
noticed concentrations of bowheads in the study area. Thus, bowheads in
the Sea of Okhotsk were once called "forgotten whales" by researchers.
WWF welcomed the creation a nature sanctuary in the region
[61]
Possibly, vagrants from this population occasionally reach into Asian nations such as off Japan or
Korean Peninsula (although this record might or might not be of a
right whale[62]). First documented report of the species in Japanese waters was of a strayed infant (7 m [23 ft]) caught in
Osaka Bay on 23 June 1969,
[63] and the first living sighting was of a 10 m (33 ft) juvenile around
Shiretoko Peninsula (the southernmost of
ice floe range in the northern hemisphere) on 21 to 23 June 2015.
[64] Fossils have been excavated on
Hokkaido,
[65] but it is unclear whether or not northern coasts of Japan once had been included in seasonal or occasional migration ranges.
Genetic studies suggest Okhotsk population share common ancestry with
whales in Bering-Chukchi-Beaufort Seas, and repeated mixings had
occurred between whales in two seas.
[66]
Svalbard-Barents Sea
The most endangered but historically largest of all bowhead populations is the Svalbard/Spitsbergen population.
[67] Occurring normally in
Fram Strait,
[68] Barents Sea and
Severnaya Zemlya along
Kara Sea[45] to
Laptev Sea and
East Siberian Sea regions, these whales were seen in entire coastal regions in European and Russian Arctic, even reaching to
Icelandic and
Scandinavian coasts and
Jan Mayen in
Greenland Sea, and west of
Cape Farewell and western
Greenland coasts.
[69] Also, bowheads in this stock were possibly once abundant in areas adjacent to the
White Sea region, where few or no animals currently migrate, such as the
Kola and
Kanin Peninsula. Today, the number of sightings in elsewhere are very small,
[70] but with increasing regularities
[71] with whales having strong regional connections.
[72] Whales have also started approaching townships and inhabited areas such as around
Longyearbyen.
[73] The waters around the marine mammal sanctuary
[74] of
Franz Josef Land is possibly functioning as the most important habitat for this population.
[75][76]
Current status of population structure of this stock is unclear;
whether they are remnant of the historic Svalbard group, re-colonized
individuals from other stocks, or if a mixing of these two or more
stocks had taken place. In 2015, discoveries of the refuge along eastern
Greenland where whaling ships could not reach due to ice floes
[77] and largest numbers of whales (80–100 individuals) ever sighted between Spitsbergen and Greenland
[78]
indicate that more whales than previously considered survived whaling
periods, and flows from the other populations are possible.
Possible moulting area on Baffin Island
During
expeditions by a tour operator 'Arctic Kingdom', a large group of
bowheads seemingly involved in courtship activities were discovered in
very shallow bays in south of
Qikiqtarjuaq in 2012.
[79] Floating skins and rubbing behaviors at sea bottom indicated possible
moulting
had taken place. Moulting behaviors had never or had seldomly been
documented for this species before. This area is an important habitat
for whales that were observed to be relatively active and to interact
with humans positively, or to rest on sea floors. These whales belong to
Davis Strait stock.
Isabella Bay in
Niginganiq National Wildlife Area
is the first wildlife sanctuary in the world to be designed specially
for bowhead whales. However, moultings have not been recorded in this
area due to environmental factors.
[80]
Predation
The principal predators of bowheads are
humans.
[81][dubious – discuss] Killer whales are also known predators.
[82] Bowheads seek the safety of the ice and shallow waters when threatened by killer whales.
[21]
Whaling
Eighteenth century engraving showing Dutch whalers hunting bowhead whales in the
Arctic
The bowhead whale has been
hunted for
blubber, meat,
oil, bones, and
baleen. Like the
right whale, it swims slowly, and floats after death, making it ideal for whaling.
[83] Before commercial whaling, they were estimated to number 50,000.
[84]
Commercial bowhead whaling began in the 16th century, when the Basques killed them as they migrated south through the
Strait of Belle Isle in the fall and early winter. In 1611, the first whaling expedition sailed to
Spitsbergen.
By mid-century, the population(s) there had practically been wiped out,
forcing whalers to voyage into the "West Ice"—the pack ice off
Greenland's east coast. By 1719, they had reached the
Davis Strait, and by the first quarter of the 19th century,
Baffin Bay.
[85]
In the North Pacific, the first bowheads were taken off the eastern coast of Kamchatka by the Danish whaleship
Neptun, Captain Thomas Sodring, in 1845.
[17] In 1847, the first bowheads were caught in the Sea of Okhotsk, and the following year, Captain
Thomas Welcome Roys, in the bark
Superior, of
Sag Harbor, caught the first bowheads in the
Bering Strait
region. By 1849, 50 ships were hunting bowheads in each area. By 1852,
220 ships were cruising around the Bering Strait region, which killed
over 2,600 whales. Between 1854 and 1857, the fleet shifted to the Sea
of Okhotsk, where 100–160 ships cruised annually. During 1858–1860, the
ships shifted back to the Bering Strait region, where the majority of
the fleet would cruise during the summer up until the early 20th
century.
[86]
An estimated 18,600 bowheads were killed in the Bering Strait region
between 1848 and 1914, with 60% of the total being reached within the
first two decades. An estimated 18,000 bowheads were killed in the Sea
of Okhotsk during 1847–1867, 80% in the first decade.
[87]
Bowheads were first taken along the pack ice in the northeastern Sea of Okhotsk, then in
Tausk Bay and Northeast Gulf (
Shelikhov Gulf). Soon, ships expanded to the west, catching them around
Iony Island and then around the
Shantar Islands. In the Western Arctic, they mainly caught them in the
Anadyr Gulf, the Bering Strait, and around
St. Lawrence Island. They later spread to the western
Beaufort Sea (1854) and the
Mackenzie River delta (1889).
[86]
Commercial whaling, the principal cause of the population decline, is over. Bowhead whales are now hunted on a
subsistence level by
native peoples of North America.
[88]
Subsistence whaling in Alaska
Some Alaska Native peoples continue by tradition to hunt bowhead and beluga whales on a
subsistence level, with low annual bowhead total quotas set by the
International Whaling Commission in conjunction with individual village limits set by the
Alaska Eskimo Whaling Commission.
[89]
Bowhead hunting is limited to whaling crews which are:
For the Native peoples of Alaska, bowhead subsistence hunting occurs
during the northward spring migrations based from the ice and from small
boats during the returning fall migrations.
[90]
Conservation
The bowhead is listed in Appendix I by
CITES (that is, "threatened with extinction"). Some populations are listed by the
National Marine Fisheries Service as "endangered" under the auspices of the United States'
Endangered Species Act. The
IUCN Red List data are as follows:
[83]
The bowhead whale is listed in Appendix I
[92] of the Convention on the Conservation of Migratory Species of Wild Animals (
CMS),
as this species has been categorized as being in danger of extinction
throughout all or a significant proportion of their range. CMS Parties
strive towards strictly protecting these animals, conserving or
restoring the places where they live, mitigating obstacles to migration,
and controlling other factors that might endanger them.
[83]
Gallery
Media related to
Balaena mysticetus at Wikimedia Commons
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Cavorting whale in northwestern part of Sea of Okhotsk
[58]
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-
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Whale showing one of pectoral fins
-
Tip of whitish chin visible
-
Map of the bowhead whale ranges centered
over the
North Pole
Niagara Falls Aviary, Canada
Female in Kenya
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