Suzy's Animals of the World Blog: THE BOWHEAD WHALES

The bowhead whale (Balaena mysticetus) is a species of the right whale family Balaenidae, in suborder Mysticeti and genus Balaena. A stocky dark-colored whale without a dorsal fin, it can grow to 20 m (66 ft) in length. This thick-bodied species can weigh 75 tonnes (74 long tons; 83 short tons) to 100 tonnes (98 long tons; 110 short tons),^[3] second only to the blue whale, although the bowhead's maximum length is less than several other whales. It lives entirely in fertile Arctic and sub-Arctic waters, unlike other whales that migrate to feed or reproduce to low latitude waters. It was also known as Greenland right whale or Arctic whale. American whalemen called it 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. Its population was severely reduced before a 1966 moratorium. The population is estimated to be over 24,900 worldwide, down from an estimated 50,000 before whaling.^{[citation needed]}

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Taxonomy

Description

Resting on water surface in Foxe Basin

The bowhead whale has a robust, dark-colored body, no dorsal fin and a strongly bowed lower jaw and narrow upper jaw. Its baleen, the longest of any whale at 3 m (9.8 ft), strains tiny prey from the water. The whale has a massive bony skull which it uses to break through the Arctic ice to breathe. Inuit hunters have reported them surfacing through 60 cm (24 in) of ice. The bowhead whale has paired blowholes that spout a blow 20 feet high. It is of comparable size to the three species of right whale. According to the 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 the spring of 1813. He also spoke of one caught near Spitsbergen around 1800 that was allegedly nearly 21.3 m (70 ft) in length, but it doesn't appear to have been actually measured.^[12] The longest reliably measured of each sex were a 16.2 m (53 ft) male and an 18 m (59 ft) female, both harvested and landed in Alaska.^[13] Females are larger than males. Its blubber is the thickest of any animal, averaging 43–50 cm (17–20 in).
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 crossed ice-covered inlets and straits to exchange genes between Atlantic and Pacific populations. This conclusion derived from analyzing maternal lineage using mitochondrial DNA, most likely because of whaling and climatic cooling between the 16th and 19th centuries — known as the Little Ice Age — which reduced the whales’ summer habitat.^[14]
A recent discovery has elucidated the function of the Bowhead's large palatal retial organ. The bulbous ridge of highly vascularized tissue, termed the corpus cavernosum maxillaris, extends along the centre of the hard plate, forming two large lobes at the rostral palate. The tissue is histologically similar to the corpus cavernosum of the mammalian penis. It's hypothesized that this organ provides a mechanism of cooling for the whale (which is normally protected from the cold Arctic waters by 40 cm of fat). During times of physical exertion, the whale must cool itself to prevent hyperthermia (and ultimately brain damage). It's believed that this organ will engorge with blood; the whale will respond by opening its mouth and allowing the cold seawater flow over the organ, cooling the blood.^[15]

Life history

Drawing of long backbone, 13 ribs (two vestigial) large, curved upper and lower jawbones that occupy 1/3 of the body, 4 multijointed "fingers" inside pectoral fin and connecting bone, enclosed in body outline

Skeleton of a bowhead whale

The bowhead is social and nonaggressive, and retreats under the ice when threatened.

Swimming

The bowhead is a slow swimmer and usually travels alone or in small herds of up to six. Though it may remain submerged as long as 40 minutes in a single dive, it is not thought to be a deep diver.
The whales' behavior can also include breaching, tail slapping, and spyhopping.

Vocalizations

The bowhead whale is highly vocal, and uses underwater sounds to communicate while traveling, feeding, and socializing. Some bowheads make long, repetitive songs that may be mating calls.

Reproduction

Lifespan

Bowheads were once thought to live 60 to 70 years, similar to other whales. However, discoveries of 19th century ivory, slate, and jade spear points in freshly killed whales in 1993, 1995, 1999, and 2007^[17] triggered research based on structures in the whale's eye, suggesting at least some individuals reached 150–200 years old (another report claimed a 90-year-old female was still fertile).^[18] The amino acid racemization process has provided the scientific basis for these claims. This process is controversial and has failed to correlate well with other dating methods.^[19]
In May 2007, a 15 m (49 ft) specimen caught off the Alaskan coast was discovered with the head of an explosive harpoon embedded deep under its neck blubber. The 3.5 inches (89 mm) arrow-shaped projectile was manufactured in New Bedford, Massachusetts, a major whaling center, around 1890, suggesting the animal may have survived a similar hunt more than a century ago.^[20]^[21]^[22]
Recent data have shown that specimens might reach 200 years of age.^[23]

Ecology

Drawing of an adult in 1884

Range and habitat

The bowhead whale is the only baleen whale to spend its entire life in and around Arctic waters. The Alaskan population spends the winter months in the southwestern Bering Sea. The group migrates northward in the spring, following openings in the pack ice, into the Chukchi and Beaufort Seas.^[24] It is confirmed that there ranges had been changing largely depending on climate changes along with right whales.^[25]

Population

The bowhead population around Alaska has increased since commercial whaling ceased. Alaska Natives continue to kill small numbers in subsistence hunts each year. This level of killing (25–40 animals annually) is not expected to affect the population's recovery. The population off Alaska's coast (the Bering-Chukchi-Beaufort stock) appears to be recovering and was about 10,500 animals as of 2001. Researchers from the School of Fisheries and Ocean Sciences have been studying the whales' feeding behaviors in the Point Barrow area. 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, but with increasing numbers in recent years.^[26]
In March, 2008, Canada's Department of Fisheries and Oceans stated the previous estimates in the eastern Arctic had undercounted, with a new estimate of 14,400 animals (range 4,800–43,000).^[27] These larger numbers correspond to prewhaling estimates, indicating this population has fully recovered. However, should climate change substantially shrink sea ice, they could be threatened by increased shipping traffic.^[28]

Whale spyhops in Ulbansky Bay, north western Okhotsk Sea.^[29]

Sea of Okhotsk

Not much is known about endangered Sea of Okhotsk population, however, nowadays whales are regularly observed at Shantar Islands, very close to shores such as at Ongachan Bay.^[30]^[31] Several companies provide whale watching services which are mostly land-based. According to Russian scientists, total population would not exceed 400 animals.^[29] Scientific researches on this population was only taken quite seldom until 2009, when researches studying Belugas noticed concentration of Bowheads in the study area. With supports from WWF, Russian scientists and nature conservationists cooperated to create a cetacean sanctuary in Magadan region which covers vast areas of north western Sea of Okhotsk including Shantar regions.^[32] Cetacean species benefitting this proposal include several critically endangered species such as North Pacific right whales, western Gray whales, and Belugas. International supports by several other organizations have been offered.^[29]

Russian Arctic

Possible moulting area on Baffin Island

During expeditions by a tour operator 'Arctic Kingdom', a large group of Bowheads seemingly involved in courtship activities was discovered in very shallow bays in south of Qikiqtarjuaq in 2012.^[43] Floating skins and rubbing behaviors at sea bottom indicate possible moulting had been taken place. Moulting behaviors had never or seldomly been documented for this species before, and this area is supposed to be 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, but moultings have not been recorded in this area due to environmental factors.^[44]

Feeding

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Unlike most other baleen whales, which primarily feed on concentrated shoals of prey species, it feeds in a manner similar to the basking shark by swimming forward with its mouth wide open, continuously filtering water through its baleen plates. Thus, it specializes in much smaller prey, such as copepods. Its mouth has a large upturning lip on the lower jaw that helps to reinforce and contain the baleen plates within its mouth, and prevents buckling or breakage of the plates due to the pressure of the water passing through them as it advances.
This is in contrast to the rorquals, which have distensible ventral pleats that they fill with prey-laden water, then expel the water while filtering out the prey through their baleen plates. They also feed on krill and copepods.

Predation

The principal predators of bowheads are humans. Occasionally, predatory attacks by orca pods have also been recorded.^[45]

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 right whales, it swims slowly, and floats after death, making it ideal for whaling. Before commercial whaling, they were estimated to number 50,000.^{[citation needed]}
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.
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. 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. 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.
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).

Inuit woman and child standing on bowhead whale after a 2002 subsistence hunt

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.

Conservation

The bowhead is listed in Appendix I by CITES (that is, "threatened with extinction"). It is 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:

Svalbard population – Critically endangered
Sea of Okhotsk subpopulation – Endangered
Baffin Bay-Davis Strait stock – Endangered
Hudson Bay-Foxe Basin stock – Vulnerable (Estimated to be 1,026 individuals in 2005 by DFO)^[46]
Bering-Chukchi-Beaufort stock – Lower risk – conservation dependent

The bowhead whale is listed on Appendix I^[47] 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 and 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.