Odobenus rosmarus


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Odobenus rosmarus
Species Authority: (Linnaeus, 1758)
Common Name(s):
English Walrus
French Morse
Spanish Morsa
Phoca rosmarus Linnaeus, 1758
Taxonomic Notes: There are three recognized subspecies: Atlantic Walrus Odobenus rosmarus rosmarus; Pacific Walrus O. r. divergens (Illiger, 1811); and Laptev Walrus O. r. laptevi (Chapskii, 1940).

It has been well established that the Atlantic and Pacific Walrus' are separate subspecies, however, the taxonomic status of the Laptev Walrus has been uncertain. It has been described as intermediate in size between the Pacific and Atlantic forms, with skull morphology similar to the Pacific subspecies (Fay 1981). Recent analyses of mitochondrial DNA and morphometric data suggest that the taxon O. r. laptevi should be abandoned and the Laptev Walrus should be recognized as the western most population of the Pacific Walrus, O. r. divergens (Lindquist et al. ms).

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Lowry, L., Kovacs, K. & Burkanov, V. (IUCN SSC Pinniped Specialist Group)
Reviewer(s): Kovacs, K. & Lowry, L. (Pinniped Red List Authority)
Although the global population is undoubtedly still quite large, there is evidence of declining populations in two of the subspecies. Climate change is expected to have negative consequences for Walruses, and particularly severe consequences for the Pacific subspecies. Additionally, little recent information is available regarding current population sizes and trends throughout much of the Walrus’s range. At this time, this species must be classified as Data Deficient.

Geographic Range [top]

Range Description:Walruses have a discontinuous circumpolar Arctic and sub-Arctic distribution (Fay 1981, Rice 1998). The Pacific subspecies is normally found from the Bering and Chukchi Seas to the Laptev Sea in the west and the western Beaufort Sea in the east, with vagrants south into the North Pacific Ocean to Japan and to southcentral Alaska (Fay 1982). The Atlantic subspecies occurs in numerous subpopulations from the eastern Canadian Arctic and Greenland to the western Kara Sea, including the Barents, White and Pechora Seas, and Svalbard and Franz Josef Land (Committee on the Status of Endangered Wildlife in Canada 2006, North Atlantic Marine Mammal Commission, undated). Historically, Atlantic walruses occurred south to the Gulf of St Lawrence in the northwestern North Atlantic. Vagrants have been reported from New England, Iceland and in western Europe south to the Bay of Biscay. All subspecies of Walruses are found in relatively shallow continental shelf areas and seldom occur in deeper waters.
Canada; Greenland; Norway; Russian Federation; Svalbard and Jan Mayen; United States
Belgium; Denmark; Finland; France; Germany; Iceland; Ireland; Japan; Netherlands; Spain; Sweden; United Kingdom
FAO Marine Fishing Areas:
Arctic Sea; Atlantic – northeast; Atlantic – northwest; Pacific – northeast; Pacific – northwest
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: The Pacific Walrus population recovered from a depleted state in 1950 to historical high levels in the 1980s (Fay et al. 1997). The Bering-Chukchi segment of the population was estimated at approximately 230,000 in 1985 (Gilbert 1989) and 201,000 in 1990 (Gilbert et al. 1992). However, characteristics of Walrus behaviour and difficulties associated with conducting surveys resulted in estimates with low precision (Gilbert 1999). The current population size in the Bering-Chukchi region is unknown (U.S. Fish and Wildlife Service 2002). The number of Pacific Walrus in the Laptev Sea region was estimated at 4,000-5,000 animals according to a report cited in Fay (1982), but the current abundance in that region is also unknown.

Changes in the abundance of Atlantic Walrus in various regions during the past 45 years are unclear (Committee on the Status of Endangered Wildlife in Canada 2006, North Atlantic Marine Mammal Commission undated). Modelling indicates that the Walrus populations in West Greenland and the North Water have been in steady decline, while the population in East Greenland has been increasing (Witting and Born 2005). Walrus numbers at Svalbard have increased slowly during 1993-2006 (Lydersen et al. 2008). The current total abundance of Atlantic Walrus is very poorly known, but the most recent information suggests a population size of perhaps 18,000-20,000 (Committee on the Status of Endangered Wildlife in Canada 2006, North Atlantic Marine Mammal Commission undated). The current global population trend is unknown.

Although female Walrus can ovulate at four years of age, the majority do not give birth until they are 7-8 years old and usually only produce one calf every three years. Gestation lasts 15 months, including a delay of implantation time of 3-3.5 months. The period of calf dependency is long, regularly lasting two years and sometimes longer. Males become sexually mature between 7-10 years old, but are not physically and socially mature enough to successfully compete for breeding opportunities until they are approximately 15 years old. Longevity is approximately 40 years (Fay 1981).

The Committee on the Status of Endangered Wildlife in Canada (2006) gives the generation time for Atlantic Walrus, calculated as the average of ages of the youngest and oldest animal giving birth, as 21 years. However, because young animals are more common in the population and older females may exhibit reproductive senility this does not correspond to the IUCN definition. The average age of female Pacific walrus in the Alaska Native harvest is approximately 15 years (Garlich-Miller et al. 2006), which provides a more reasonable estimate of the generation time.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: Walruses are one of the largest pinnipeds. In the Pacific, males reach about 3.6 m in length and weigh 880-1,557 kg; adult females are about 3 m and 580-1,039 kg. In the Atlantic adults are slightly shorter and lighter. Newborns are 1-1.4 m and weigh 33-85 kg (Fay 1981). Walrus are characterized by their large tusks, which are well-developed in both males and females. Tusks are used for interspecific aggression, defense against predators (Polar Bears and Killer Whales) and as an aid for hauling-out on ice.

Courtship and mating occur in the winter. It is believed that Walruses are polygynous and that the males establish small aquatic territories where they vigorously vocalize and display adjacent to females hauled-out on ice floes (Fay 1981).

Walruses haul out on ice floes and beaches on islands or remote stretches of mainland coastlines. They are very gregarious animals and are frequently found in tight groups that number from the tens to the thousands. Pacific Walruses spend most of their lives associated with sea ice and migrate with the ice as it expands and moves south in the winter and breaks up and retreats in the spring and summer. Males often separate from the females in late spring and during the summer they use land haulouts some distance from sea ice, while the females, their calves, and most of the juveniles follow the retreating sea ice edge north (Fay 1982). The situation is somewhat different for Atlantic Walrus, with animals of all sex/age categories using terrestrial haulouts during summer months (Born 2005). At sea, Walruses can be found alone or in aggregations.

Walruses are primarily bottom feeders and shallow divers (Fay 1982, Born 2005). Most prey taken is found in the upper few centimeters of sediment, or lives on or just above the bottom. A wide variety of benthic invertebrates, with several species of clams, make up the majority of food for most animals. Their diet also includes other species of molluscs, and many species of worms, snails, soft shell crabs, amphipods, shrimp, sea cucumbers, tunicates, and slow-moving fish. Some individuals prey on seals, small whales and seabirds and may occasionally scavenge marine mammal carcasses.
Systems: Terrestrial; Marine

Threats [top]

Major Threat(s): Native people of the Arctic have depended on Walruses for food, hides, ivory and bones since first contact, and subsistence harvests of both subspecies continue today in most parts of their ranges. All Walrus populations were severely depleted by episodic commercial hunting that was heaviest from the 18th through to the mid-20th centuries.

Direct conflicts with fisheries are uncommon (U.S. Fish and Wildlife Service 2002); however, trawl fisheries could disturb important benthic feeding areas (Committee on the Status of Endangered Wildlife in Canada 2006). Human disturbance at land-based haul-out sites, low-level aircraft over-flights and near-shore passage of vessels can have serious effects on Walruses out of the water, as they are highly susceptible to disturbance and easily panicked into stampedes (Fay and Kelly 1980).

Global warming and any associated reduction in the extent, timing, and characteristics of seasonal sea ice cover could negatively affect Walruses, especially the Pacific population. Declining sea ice reduces suitable strata for pupping and breeding aggregation and limits access to offshore feeding areas (Tynan and DeMaster 1997, Moore 2005, Laidre et al. in press). In the Atlantic where the use of coastal haulouts is more widespread, reduced sea ice cover could increase feeding opportunities for Walruses (Born 2005).

Reduction in sea ice could also lead to the addition of commercial sea lanes in currently rarely visited portions of the Walruses’ range, with increased risk of spills and discharge of pollutants, disturbance and coastal development (Reijnders et al. 1993, Tynan and Demaster 1997, Moore 2005). A history of poor international cooperation, crude population monitoring methods and delayed management responses has led to speculation that future management actions in response to population declines of Pacific Walruses may not be taken soon enough to be effective (Fay et al. 1989).

Conservation Actions [top]

Conservation Actions: The population of Canada is listed on CITES Appendix III. Since 1972 coastal Alaska Natives have hunted Walruses in the United States for subsistence purposes under an exemption provided in the Marine Mammal Protection Act. No quotas or limits have been established, but all animals taken are required to be harvested in a non-wasteful manner. Alaska Natives work with the responsible management agency (U.S. Fish and Wildlife Service) to co-manage Walrus hunting. Regulations on harvest are in place in Canada, the Russian Federation, and Greenland. Norway prohibits all hunting at Svalbard (North Atlantic Marine Mammal Commission undated).

Bibliography [top]

Born, E. W. 2005. An assessment of the effects of hunting and climate on walruses in Greenland. University of Oslo.

Committee on the Status of Endangered Wildlife in Canada. 2006. COSEWIC assessment and update status report on the Atlantic walrus Odobenus rosmarus rosmarus in Canada. Ottawa, Canada Available at: http://www.sararegistry.gc.ca/virtual_sara/files/cosewic/sr_atlantic_walrus_e.pdf.

Fay, F.H. 1981. Walrus Odobenus rosmarus (Linneaus, 1758). In: S.H. Ridgway and R. Harrison (eds), Handbook of Marine Mammals, Vol. 1: The walrus, sea lions, fur seals, and sea otter, pp. 1-23. Academic Press.

Fay, F.H. 1982. Ecology and biology of the Pacific walrus, Odobenus rosmarus divergens Illiger. North American Fauna 74:1-279.

Fay, F.H. and Kelly, B.P. 1980. Mass natural mortality of walruses (Odobenus rosmarus) at St. Lawrence Island, Bering Sea, autumn 1978. Arctic 33:226-245.

Fay, F.H., Eberhardt, L.L., Kelly, B.P., Burns, J.J. and Quakenbush, L.T. 1997. Status of the Pacific walrus population, 1950-1989. Marine Mammal Science 13(4): 537-565.

Fay, F.H., Kelly, B.P. and Sease, J.L. 1989. Managing the exploitation of Pacific walruses: a tragedy of delayed response and poor communication. Marine Mammal Science 5: 1-16.

Garlich-Miller, J.L., Quakenbush, L.T. and Bromaghin, J.F. 2006. Trends in age structure and productivity of Pacific walruses harvested in the Bering Strait region of Alaska, 1952-2002. Marine Mammal Science 22(4): 880-896.

Gilbert, J., Fedoseev, G., Seagars, D., Razlivalov, E. and Lachugin, A. 1992. Aerial census of Pacific walrus, 1990. U.S. Fish and Wildlife Service Administrative Report R7/MMM 92-1.

Gilbert, J. R. 1989. Aerial census of Pacific walruses in the Chukchi Sea, 1985. Marine Mammal Science 5: 27-28.

Gilbert, J.R. 1999. Review of previous Pacific walrus surveys to develop improved survey designs. In: G.W. Garner, S.C. Amstrup, J.L. Laake, B.F.J. Manly, L.L. McDonald and D.G. Robertson (eds), Marine Mammal Survey and Assessment Methods, pp. 75-84. A.A. Balkema, Rotterdam, The Netherlands.

IUCN. 2008. 2008 IUCN Red List of Threatened Species. Available at: http://www.iucnredlist.org. (Accessed: 5 October 2008).

Laidre, K.L., Stirling, I., Lowry, L.F., Wiig, Ø., Heide-Jørgensen, M.P. and Ferguson, S.H. 2008. Quantifying the sensitivity of Arctic marine mammals to climate-induced habitat change. Ecological Applications 18: S97-S125.

Lindqvist, C., Bachmann, L., Andersen, L. W., Born, E. W., Arnason, U., Kovacs, K. M., Lydersen, C., Abramov, A. V. and Wiig, Ø. Unpublished. The Laptev Sea walrus Odobenus rosmarus laptevi: an enigma revisited.

Lydersen, C., Aars, J. and Kovacs. K. M. 2008. Estimating the number of walruses in Svalbard based on aerial surveys and behavioural data from satellite telemetry. Arctic 61(2): 119-128.

Moore, S. E. 2005. Long-term environmental change and marine mammals. In: J. E. Reynolds III, W. F. Perrin, R. R. Reeves, S. Montgomery and T. J. Ragen (eds), Marine Mammal Research Conservation Beyond Crisis, pp. 137-148. Johns Hopkins University Press., Baltimore, USA.

North Atlantic Marine Mammal Commission. Undated. Status of marine mammals in the North Atlantic: the Atlantic walrus. Available at: http://www.nammco.no/webcronize/images/Nammco/654.pdf.

Reijnders, P., Brasseur, S., van der Toorn, J., van der Wolf, P., Boyd, I., Harwood, J., Lavigne, D. and Lowry, L. 1993. Seals, fur seals, sea lions, and walrus. Status survey and conservation action plan. IUCN Seal Specialist Group.

Rice, D.W. 1998. Marine Mammals of the World: Systematics and Distribution. Society for Marine Mammalogy, Lawrence, Kansas.

Stirling, I. and Derocher, A. E. 1993. Possible impacts of climatic warming on polar bears. Arctic 46: 240-245.

Tynan, C. T. and DeMaster, D. P. 1997. Observations and predictions of Arctic climate change potential effects of marine mammals. Arctic 50: 308-322.

U.S. Fish and Wildlife Service. 2002. Pacfic walrus (Odobenus rosmarus divergens): Alaska stock. Available at: http://alaska.fws.gov/fisheries/mmm/walrus/pdf/Final_%20Pacific_Walrus_SAR.pdf.

Witting, L. and Born, E. 2005. An assessment of Greenland walrus populations. ICES Journal of Marine Science 62: 266–285.

Citation: Lowry, L., Kovacs, K. & Burkanov, V. (IUCN SSC Pinniped Specialist Group) 2008. Odobenus rosmarus. In: The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 30 June 2015.
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