Bowhead Whale

Balaena mysticetus

Description

A mature bowhead whale, Balaena mysticetus, ranges from 50-65 ft (15-20 m) in length and can weigh up to 50 tons (45 metric tons). The body is very stout with the head composing more than one-third of the body length. The mouth bows gently upward. The color is almost always solid black (occasionally charcoal gray) except for a large white chin patch. Flippers are broad and spatula-shaped. This whale lacks a dorsal fin, and its spout is V-shaped.

This species is also commonly known as the Greenland right whale, Arctic right whale, or great polar whale. It is called the "kiralick" by the Alaskan Eskimos.

Behavior

The bowhead usually travels alone or in very small groups (two or three), although larger groups of up to 30 have been observed in rich feeding waters. The bowhead spends its life along the edge of the Arctic ice pack, retreating before its advance in winter and following its retreat in summer.

Food habit studies conducted on 35 bowhead whales (21 males and 14 females) harvested between 1975 and 1989 indicated that bowheads feed on crustacean zooplankton, particularly euphausiids and copepods. Age-related differences were difficult to establish given the limited sample size; however, slightly higher levels of epibenthic organisms were found in the stomachs of small whales, and it appears that copepods become increasingly more important in the diet of larger whales. As evidenced in stomach contents collected between April and June, some bowhead whales feed opportunistically during the spring migration. Bow-head whales were once thought to be exclusively skimmers, taking food at the surface by swimming slowly with their mouths open, straining the water through the baleen. More recent research concludes that the bowhead is a bottom feeder; its fine baleen hairs allow it to strain very small organisms.

Although apparent sexual activity occurs among bowhead whales most months of the year, studies of bowhead fetuses indicate conception typically occurs during late winter or early spring. Calves are usually born between April and early June during the spring migration, probably peaking in May. Pregnancy rates suggest that mature female bow-heads have calving intervals of 3.5-7.1 years.

The gestation period is unknown but has been estimated at 12-16 months. Weaning occurs 9-15 months postpartum. Growth rates appear to slow after weaning. Small bowheads re-identified between years had growth rates of less than 3 ft (1 m) per year; bowhead whales grow slowly, taking nearly two decades to reach sexual maturity. This growth rate is much slower than that of other baleen whales. Conventional techniques to age bowhead whales have been considered unsuccessful, in part because of the poor correlation between whale size and indicated age, but some evidence, such as ivory or stone harpoon heads found in five recently harvested whales, suggest that bowhead whales may live 50 years to 75 years.

The call of the bowhead is very distinctive and is repeated over and over.

Habitat

This whale is found in Arctic waters around the edges of the polar ice cap.

Distribution

Bowhead whales are grouped into five subpopulations: Hudson Bay, Baffin Bay, Sea of Okhotsk, the Bering Sea, and the Greenland and Barents Sea. Once quite common, the bowhead has been so decimated by whaling that it is now one of the most endangered whales. From 1660 to 1912, about 90,000 bowhead whales were harvested by commercial whalers.

The bowhead has been hunted until its numbers are very low, particularly in the eastern Arctic. Alaskan bowheads are more abundant, but Greenland populations have been reduced almost to zero. Estimates of the number of surviving whales range from 2,800 to 5,000. From 1992 to 1994, 113 bowhead whales were landed and 35 were struck but lost during native subsistence hunts in Alaska

Threats

Threats to the bowhead whale include collision with ships, entanglement in commercial fishing nets, degradation of habitat, and the resumption of commercial whaling. The IWC warns that some of the feeding waters for the Arctic populations are candidates for leasing to oil and gas exploration, especially in the Beaufort and Chukchi Seas. However, the IWC also authorized the incidental take of bowheads with no limit to the number that could be killed.

It is not known whether bowhead whales suffer from stress-induced bacterial infections similar to those observed in captive cetaceans (1987). Studies of harvested bowhead whales have provided information on bacterial, mycotic and viral infections but not the level to which they contribute to mortality and morbidity. How much these viruses contribute to natural mortality and possibly to reduced reproduction in the bowhead whale population is unknown.

Evidence of ice entrapment and predation by killer whales, Orcinus orca, has been documented in almost every bowhead whale stock. The percentage of whales entrapped in ice is considered to be small, given that this species is so strongly associated with ice. Of 195 whales examined during the Alaskan subsistence harvest (1976-92), eight had been wounded by killer whales. Hunters on St. Lawrence Island reported two small bowhead whales found dead as a result of killer whale attacks (1994).

Clearly, bowhead whale stocks are slow to recover, and some might not recover at all. The Spits"tens"-bergen stock was reduced from 24,000 to a few "tens" of whales and has not recovered in the past 80 years. The Davis Strait and Hudson Bay stocks declined from about 12,300 whales to less than 450 currently, although significant whaling has not occurred in 80 years. The Okhotsk Sea stock was originally around 3,000 whales, but after severe whaling which ended over 100 years ago, there are still only 300-400 whales. The Bering Sea may have had a stock that was eliminated, except for the component that migrated to the Beaufort Sea. This stock was reduced from at least 10,300 animals, and has been recovering slowly over the past 80 years to a current population of about 8,000. There is evidence that bowhead whales are long-lived animals. It is therefore possible that in the greatly reduced stocks, some of the animals have survived since the termination of commercial whaling, but fecundity rates are so low that very few new whales are being added to the respective stocks. Calving intervals of 3-4 years and the possibility that bowhead whales do not become sexually mature until they are 20 years old may, in part, explain these slow recovery rates in stocks with only a few hundred whales.

Impacts from industrial development (particularly offshore oil extraction) are of concern as most habitat of the Bering stock of bowheads is within active or potential lease zones. But studies indicate that bowhead behavior is often temporarily affected when exposed to close approaches by ships, seismic vessels, and aircraft. Reactions are less obvious when the noise source is fairly constant, such as with distant seismic or drilling work, but migrating bowheads sometimes adjust their course to divert around stationary sources of man-made noise.

Conservation and Recovery

The bowhead is now protected by international treaty, under the International Whaling Commission (IWC). During the 1970s, a controversy arose concerning bowhead hunting by Alaskan Inupiat Eskimos, who traditionally depended upon whales for their subsistence. Most member countries to the convention wanted to set a zero quota, and debate raged in the U.S. between conservationists, who wanted to stop all hunting, and Eskimos, who pleaded the importance of the whale for subsistence and for the maintenance of tribal culture. Eventually, the subsistence argument was rejected, but it was determined that some whale hunting was important for maintaining cultural continuity. A compromise quota was set by the IWC that allows the Inupiats to take a few whales per year, killed and successfully landed. A quota of 204 bowhead whales has been set for 1995-98, based on a stated need for 51 whales per year to be divided among ten Alaskan native villages. Requests to harvest bowhead whales have also been put forth by Canadian and Russian natives. In 1991, Aklavik hunters in the western Canadian Arctic requested a permit to kill one or strike two bowhead whales from the Bering Sea stock. Permission was granted by the Canadian government in August 1991, and one whale was harvested in Mackenzie Bay in the autumn of 1991. Additional licenses were granted in 1993 and 1994, though bowhead whales were not harvested in either year.

The IWC is the primary body responsible for conservation and management of bowhead whale populations worldwide. All stocks of bowhead whales are classified as "protected" by the IWC. The United States further classified all bowhead whales as Endangered under the ESA and depleted under the MMPA. Currently, the bowhead whales in the Bering-Chukchi-Beaufort Seas represent the largest surviving stock. This is the only stock, mandated by the IWC and through exemptions under the ESA and MMPA, still harvested by aboriginal hunters in Alaska. Thus far, a quota to harvest bowhead whales from the Bering Sea stock and the other stocks has not been provided to Russian or Canadian natives by the IWC. As determined by the IWC's Scientific Committee, "the total of whales landed in the four years 1995-98 should not exceed 204, with a maximum number of 68 strikes in 1995, 67 in 1996, 66 in 1997, and 65 in 1998." Any unused portion of the strike quota will be carried forward from that year and added to the strike quota of any subsequent years, provided that no more than 10 strikes are added to the strike quota for any one year. The average number of whales harvested per year from 1989 to 1993, including those struck and lost, was 42.

Since 1981, the harvest has been monitored by the Alaska Eskimo Whaling Commission (AEWC) through a Cooperative Agreement with the National Oceanic and Atmospheric Administration (NOAA). This Cooperative Agreement will remain in effect until 2000. Also since 1981, the AEWC has channeled funds to the North Slope Borough (NSB) for censuring the bowhead whale population as it migrates past Point Barrow in the spring. The AEWC has also been responsible for allocating IWC quotas among its member communities and has worked to improve hunting methods and technology to reduce the number of whales struck but lost. Emphasis has been placed on promoting understanding of the needs of native Alaskan whalers and obtaining quotas that will meet these needs while still ensuring recovery of the bowhead whale population. Roles have included habitat management and protection in light of increased commercial activity in the Arctic.

Contacts

National Marine Mammal Laboratory
Alaska Fisheries Science Center
7600 Sand Point Way NE
Bin C15700
Seattle, Washington 98115-0070

U.S. Fish and Wildlife Service
Division of Endangered Species
1011 E. Tudor Road
Anchorage, Alaska 99503
http://alaska.fws.gov/

References

Baker, M. L. 1987. Whales, Dolphins, and Porpoises of the World. Doubleday, Garden City.

Evans, P. G. 1987. The Natural History of Whales and Dolphins. Facts on File Publications, New York.

Haley, D., ed. 1978. Marine Mammals of Eastern North Pacific and Arctic Waters. Pacific Search Press, Seattle.

Hoyt, E. 1984. The Whale Watcher's Handbook. Doubleday, Garden City.

Mitchell, E. D., and R. Reeves. 1980. "The Alaska Bowhead Problem: A Commentary." Arctic 33:686-723.

Nerini, M. K., et al. 1984. "Life History of the Bow-head Whale." Journal of Zoology, London 204:443-468.

Reeves, R. R., et al. 1983. "Distribution and Migration of the Bowhead Whale in the Eastern North American Arctic." Arctic 36(1):5-64.

U.S. Department of Commerce/NOAA/NMFS/AFSC/NMML. 1998. "The Bowhead Whale, Balaena mysticetus : Its Historic and Current Status." Five Year Agency Survey of Bowhead Whale Populations.

Wursig, B., et al. 1986. "Behavior of BowheadWhales, Summering in the Beaufort Sea: A Summary." Report of the International Whaling Commission Special Issue 8:167-176.

bowhead whale (Balaena mysticetus) See BALAENIDAE.

Balaena mysticetus (bowhead whale) See BALAENIDAE.