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Odobenus rosmaruswalrus

By Hillary Baker

Geographic Range

Walruses (Odobenus rosmarus) are found in Arctic regions of the world. There are three subspecies. Pacific walruses (Odobenus roasmarus divergens) live primarily in the Bering Sea. In warm summer months it could travel as far the Beaufort Sea and the East Siberian Sea. Atlantic walruses (Odobenus rosmarus rosmarus) resides in the eastern and western Atlantic Ocean. Laptev walruses (Odobenus rosmarus laptevi) are found in the Laptev Sea. Laptev walruses are the smallest subspecies of walrus with only a few thousand living currently in the Laptev Sea and the least is known about them. ("Walrus", 2011; Kastelein, 2008)

Habitat

Walruses inhabit areas in the Arctic that are largely made up of ice. Walruses prefer areas with shallow water so they can easily access food. This slow moving marine mammal spends the majority of its time in or around water. Females spend more time on ice opposed to the males, who spend more of their time on sand or boulder beaches. Walruses migrate north during the summer and south in the winter. The migrations ensure that the walruses can be where the most optimal ice is found. Optimal is defined as relatively thin ice but thick enough to hold the enormous weight of their bodies. ("Walrus", 2011; Feldhamer, et al., 2003; Kastelein, 2008)

  • Terrestrial Biomes
  • icecap

Physical Description

Walruses are one of the largest pinnipeds. The Pacific walruses tend to have a larger body mass than the Atlantic walruses. This animal is known for their massive tusks, which are really just enlarged canine teeth. These tusks can break through 20 cm of ice. They also assist walruses in climbing out of the water and onto the ice. The tusks can be used for the walruses to defend themselves from larger predators and are also a way to establish dominance and a hierarchy among walruses. Tusks can grow to a length of 90 cm but the average size is roughly 50 cm. Walruses have thick skin that ranges from a light grey to a yellowish brown color. Walrus pups skin color differs from the adult, because they are usually solid grey, while adults can range in colors. The skin thickness varies across the body but is usually 2 to 4 cm thick. The layer of blubber underneath the skin can be as thick as 25.4 cm. ("Walrus", 2011; Berta, et al., 2006; Feldhamer, et al., 2003; Kastelein, 2008)

Walruses have short fur in most areas of their bodies except their appendages. Walruses have whiskers to help them feel around on the ocean floor. They have relatively small eyes because they rely mainly on sense of touch to find food. They have short front flippers not only to swim but also to assist them on land. It uses its hind flippers as a motor to move its large body through the waters with the help of the front flippers to navigate which direction it will go in. Male have greater mass than females, weighing up to 1200 to 1500 kg and can be as long as 320 cm. Females of the same age can weigh 600 to 850 kg and grow to a length of 270 cm. Males also have longer and thicker tusks than females. Males usually have thicker skin than females as well. ("Walrus", 2011; Berta, et al., 2006; Feldhamer, et al., 2003; Kastelein, 2008)

  • Sexual Dimorphism
  • male larger
  • Range mass
    600 to 1500 kg
    1321.59 to 3303.96 lb
  • Average mass
    1000 kg
    2202.64 lb
  • Range length
    270 to 320 cm
    106.30 to 125.98 in
  • Average length
    300 cm
    118.11 in

Reproduction

Walruses are polygynous, meaning that one male usually mates with many females. Males have many mating calls and noises they make to attract females during mating season and in order to mark their territory. Underwater, the males make bell whistling noises and thumping noises to get the attention of females. These noises, not only attract females, but also serve as a warning to other male walruses. These noises are meant to intimidate other walruses. When it comes to mating, usually the strongest, largest and oldest of the males get to mate with the females. Tusk fights occur between males over who gets to mate with a group of females either on land or in water. Sometimes these fights can be very gruesome and even fatal. ("Walrus", 2011; Fishbach, et al., 2008; Kastelein, 2008)

Female walruses sexually mature between the ages of 5 and 7. Males sexually mature around ages 7 and 10 but don’t mate until they are approximately 15 years old, when they are socially mature. During the winter and summer, both male and female walruses gather in the thousands to breed. Both sexes congregate in their haul-out sites, which are rocky or sandy beaches, to pick potential mates. However, mating is believed to take place in the water. Walruses produce offspring most of their lives. Females produce one calf every 3 years. The average gestation period for a female walrus is 15 months, which includes a 4 to 5 month delay in the egg implantation. ("Walrus", 2011; Fishbach, et al., 2008; Kastelein, 2008)

Because walruses breed between January and April, the baby walruses will be born the next year between April and June. The average weight of a walrus pup is about 60 kg with a length of 120 cm. When the calves are born, they immediately know how to swim. This, along with the mother’s protection, decreases the chance for predation. Before the calves are weaned, they live with the herd of female walruses. They are very dependent on their mothers for the first few years. At age two, they learn to scavenge for their own food and by age three, they are completely weaned. At this time, male walruses join the male herd and females stay in the female group but are independent from their mothers. ("Walrus", 2011; Feldhamer, et al., 2003; Kastelein, 2008)

  • Breeding interval
    Walruses breed once every 2 to 3 years.
  • Breeding season
    Walruses breed between January and April.
  • Range number of offspring
    1 to 1
  • Average number of offspring
    1
    AnAge
  • Average gestation period
    15 months
  • Average gestation period
    331 days
    AnAge
  • Range weaning age
    12 to 36 months
  • Range time to independence
    2 to 3 years
  • Average time to independence
    3 years
  • Range age at sexual or reproductive maturity (female)
    5 to 7 years
  • Average age at sexual or reproductive maturity (female)
    7 years
  • Range age at sexual or reproductive maturity (male)
    7 to 10 years
  • Average age at sexual or reproductive maturity (male)
    10 years

Female walruses care for their pups until the pups reach three years of age. Male walruses have no part in raising their young. (Kastelein, 2008)

  • Parental Investment
  • female parental care
  • pre-weaning/fledging
    • protecting
      • female
  • pre-independence
    • protecting
      • female

Lifespan/Longevity

The average lifespan for walruses is between 30 to 40 years in the wild. They have a high survival rate as calves due to the protection by the females. Lower life spans may be a result of poachers and hunters. In captivity, walruses have been recorded to live up to age 30. However, ingesting objects that are not meant for eating and tusk infection could prevent a long lifespan in captivity. Also, since they are in artificial surroundings, the behavior between mothers and calves may cause problems, such as malnutrition. ("Walrus", 2011; Kastelein, 2008; de Magalhaes and Costa, 2009)

  • Range lifespan
    Status: wild
    30 to 40 years
  • Range lifespan
    Status: captivity
    30 (high) years
  • Typical lifespan
    Status: wild
    30 to 40 years

Behavior

Walruses live in a hierarchal system based on age, body size, and tusk length. The older and stronger the walrus, the higher up it will be in the hierarchy. The male walruses establish dominance and compete for females by fighting with their tusks. The tusk fighting takes place while the walruses are at haul-out sites, which are usually rocky or sandy beaches near the water. The walruses go to these haul-out sites to rest and sleep. Walruses can move the fastest while in the water. Walruses are social and spend most of their time with other walruses of the same sex. Female walruses stay in one herd, while males stay in another herd until breeding time. Sometimes the packs can range from hundreds to thousands. In the winter and summer, male and females come together in large groups and get very close to each other sometimes even piling on top of each other. ("Walrus", 2011; Kastelein, 2008; Reijnders, et al., 1993)

Home Range

Home ranges have not been reported for walruses. (Kastelein, 2008)

Communication and Perception

Walruses have small eyes that are adapted to the cold environment. Some fat cells are in place to help keep the eyes warm. Some studies indicate that walruses can see in color, but the range of the color spectrum is unknown. Walruses has short-range vision and often cannot see when they are on the ocean floor scavenging for food. The whiskers, also called vibrissae, are used for feeling their way around the ocean floor. Walruses use their whiskers to help identify food or any other small objects. They can hear relatively well on land but under water, they use a system of tissue conduction to hear. This system closes their auditory meatus and only allows them to hear through their outer ear tube. Walruses are vocal mammals. They communicate during mating season, when they have mother and calf interactions, and when establishing dominance among other walruses. Walruses have a series of grunts and barks they will use in the situations described above. The Atlantic walrus and the Pacific walrus have slightly different vocalizations. A study showed that walruses could differentiate between the two different subspecies vocalizations. ("Walrus", 2011; Charrier, et al., 2010; Charrier, et al., 2011; Kastelein, 2008)

Food Habits

Walruses mainly feed on small invertebrates, most commonly consuming bivalve mollusks. It is unknown exactly how walruses find them. however it is known that walruses use their hind fins to propel them forward, while their tusks, mouth, and whiskers drag the bottom of the ocean floor in search of food. Once the walrus has obtained a mollusk, it uses a suction method to ingest the inside after its mouth and tongue have opened the shell. Occasionally a different method is used to get shellfish open by crushing them open with their rounded teeth. Due to the walrus’s diet of small organisms, large quantities are required to sustain them. Each time a walrus dives down to eat, they can consume up to 60 clams. Their dives for food usually last 5 to 20 minutes. Walruses can dive to depths of approximately 70 m. Adults require 25 kg of small benthic organisms per day. Walruses occasionally eat bigger animals such as seals and some seabirds. ("Walrus", 2011; Born, et al., 2003; Dehn, et al., 2007; Kastelein, 2008)

  • Animal Foods
  • birds
  • mammals
  • mollusks
  • aquatic crustaceans
  • other marine invertebrates

Predation

Walruses predators include killer whales and polar bears. Adults use their giant tusks as a weapon to defend themselves. The young walruses are more susceptible to predation. Humans are the main predator of walruses. (Jay, et al., 2011; Kastelein, 2008; Reijnders, et al., 1993)

Ecosystem Roles

Walruses forage mainly on molluks and other benthic organisms. Sometimes the parasite Trichinella spiralis can get inside their intestines and the intestinal lining. In extreme cases this can cause death but usually it just causes pain, sickness, and organ damage. The parasite, Toxoplasma gondii, is found in walruses and is acquired when eating bivalves. This parasite can cause Toxoplasmosis and results in death. Brucellosis causing parasites (Brucella) result in reproductive problems for walruses. This can lead to stillbirths and can result in death to the parent, as well. (Dubey, et al., 2009; Garcia, 1999; Nielsen, et al., 1996)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Walruses are extremely important to humans. Humans hunt them and use them for oil, ivory, and their hides. Many centuries ago, the natives of Alaska, Canada, and Russia hunted them for their meat and bones, which were used to make tools. Population sizes of walruses decreased greatly in the 18th century due to overhunting. Through the years, governments from various countries have put restrictions on walrus hunting. This has allowed the populations to rebound but they have never fully recovered. ("Walrus", 2011; Kastelein, 2008)

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

There are no known adverse effects of walruses on humans.

Conservation Status

According to IUCN Redlist of threatened species, walrus conservation status is currently listed as data deficient. Walruses are threatened by hunters who use them for their bones, skin, and tusks. According to IUCN redlist, there are regulations on walrus hunting in Canada, Greenland, and in the Russian Federation. In Alaska, most natives use walruses in a non-wasteful way. Walruses are fully protected in Svalbard and the Russian Atlantic under the North Atlantic Marine Mammal Commission. Another threat to this species is global warming. There is a decrease of floating ice further out at sea, which reduces their feeding areas. CITES lists walruses in appendix III. This appendix includes general information on the walrus as well as information on the walrus population and conservation. Species are listed in Appendix III not because they are globally threatened, but because countries requested help in trade control and permitting for the species' import or export. (Chivers, 2004; Jay, et al., 2011)

Contributors

Hillary Baker (author), Radford University, Karen Powers (editor), Radford University, Kiersten Newtoff (editor), Radford University, Melissa Whistleman (editor), Radford University.

Glossary

Arctic Ocean

the body of water between Europe, Asia, and North America which occurs mostly north of the Arctic circle.

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

delayed implantation

in mammals, a condition in which a fertilized egg reaches the uterus but delays its implantation in the uterine lining, sometimes for several months.

dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

food

A substance that provides both nutrients and energy to a living thing.

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

polygynous

having more than one female as a mate at one time

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

terrestrial

Living on the ground.

visual

uses sight to communicate

References

2011. Walrus. Pp. 1 in Columbia Electronic Encyclopedia, 6th Edition, Vol. 1, Sixth edition Edition. New York, NY: Columbia University Press.

Berta, A., J. Sumich, K. Kovacs. 2006. Marine Mammals: Evolutionary Biology. San Diego, California: Academic Press.

Born, E., S. Rysgaard, G. Ehlme, M. Acquarone, N. Levermann. 2003. Underwater observations of foraging free-living Atlantic walruses (Odobenus rosmarus rosmarus) and estimates of their food consumption. Polar Biology, 26/5: 348-357.

Charrier, I., T. Aubin, N. Mathevon. 2010. Mother–calf vocal communication in Atlantic walrus: a first field experimental study. Animal Cognition, 13/3: 471-482.

Charrier, I., A. Burlet, T. Aubin. 2011. Social vocal communication in captive Pacific walruses Odobenus rosmarus divergens. Mammalian Biology, 76/5: 622-627.

Chivers, C. 2004. The Evolution of the Hunt. Wildlife Conservation, 107/6: 36-41.

Dehn, L., G. Sheffield, E. Follmann, L. Duffy, D. Thomas, T. O'Hara. 2007. Feeding ecology of phocid seals and some walrus in the Alaskan and Canadian Arctic as determined by stomach contents and stable isotope analysis. Polar Biology, 30/2: 167-181.

Dubey, J., J. Mergl, E. Gehring, N. Sundar, G. Velmurugan, O. Kwok, M. Grigg, C. Su, D. Martineau. 2009. Toxoplasmosis in captive dolphins (Tursiops truncatus) and walrus (Odobenus rosmarus). Journal of Parasitology, 95: 82-85.

Feldhamer, G., B. Thompson, J. Chapman. 2003. Wild Mammals of North America: Biology, Management, and Conservation. Baltimore, Maryland: The Johns Hopkins University Press.

Fishbach, A., C. Jay, J. Jackson, L. Andersen, G. Sage, S. Talbot. 2008. Molecular method for determining sex of walruses. Journal of Wildlife Management, 72/8: 1808-1812.

Garcia, L. 1999. Practical Guide to Diagnostic Parasitology. Washington, DC: American Society for Microbiology.

Jay, C., B. Marcot, D. Douglas. 2011. Projected status of the Pacific walrus ( Odobenus rosmarus divergens) in the twenty-first century. Polar Biology, 34/7: 1065-1084.

Kastelein, R. 2008. Walrus. Pp. 1212 in W Perrin, B Würsig, J Thewissen, eds. Encyclopedia of Marine Mammals, Second Edition Edition. New York, NY: Academic Press.

Mukhametov, L., J. Siegel, O. Lyamin, J. Pryaslova. 2009. Behavioral sleep in the walrus. Behavioural Brain Research, 201/1: 80-87.

Nielsen, K., O. Nielsen, R. Stewart. 1996. Serologie evidence of Bruceila spp. exposure in Atlantic walruses (Odobenus rosmarus rosmarus) and ringed seals (Phoca hispida) of Arctic Canada. Arctic, 49/4: 383-386.

Reijnders, P., S. Brasseur, J. van der Toorn, P. van der Wolf, I. Boyd, J. Harwood, D. Lavigne, L. Lowry. 1993. Seals, Fur Seals, Sea Lions and Walrus. Gland, Switzerland: IUCN.

Skoglund, E., C. Lydersen, O. Grahl-Nielsen, T. Haug, K. Kovacs. 2010. Fatty acid composition of the blubber and dermis of adult male Atlantic walruses (Odobenus rosmarus rosmarus) in Svalbard, and their potential prey. Marine Biology Research, 6/3: 239-250.

Udevitz, M., C. Jay, A. Fischbach, J. Garlich-Miller. 2009. Modeling haul-out behavior of walruses in Bering Sea ice. Canadian Journal of Zoology, 87/12: 1111-1128.

de Magalhaes, J., J. Costa. 2009. A database of vertebrate longevity records and their relation to other life-history traits. Journal of Evolutionary Biology, 22/8: 1770-1774.

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