Kendle Kubick, Jamie Kashary, Amy Bieszke

  Until the 18th century the English name for the walrus was "morse" from the Finnish "mursu" meaning ‘whale-horse’. This was undoubtedly because of their size. The average walrus can be more than 10 feet long and weight over 2,600 pounds (Sea Lions…, 1996). In 1758 the Latin term from Linneaus, Odobenus rosmarus, meaning ‘tooth-walker’ was given because of the elongated upper canines, or tusks, that both males and females appear to use to pull themselves around on the ice.

Linnaean taxonomy has given us two and possibly a third subspecies:

• Odobenus rosmarus diverges- which lives in the northern Pacific.
• Odobenus rosmarus rosmarus- which lives in the northern Atlantic.
• Odobenus rosmarus laptevi- which recently Russian researchers have recognized as an isolated population from the Laptev Sea (Wildsanctuary, 1997).

The only difference between these three subspecies is where they are located. They are all grayish-brown in color and are known for their massive size. They manage to carry themselves around on land by turning their hind flippers and walking on all four limbs. This is how we generally see them displayed in books and on TV. However, they are very capable of traveling far distances in the water. They use their front flippers for propulsion.

Walruses need to be good at locomotion; both on ice and in water because they are in a sense forced to migrate. They inhabit the open waters near the edges of polar ice. They generally migrate with the movement of the ice, sometimes riding on the floating ice, called floes. In the winter as temperatures grow colder, the amount of ice in the polar regions begins to build up. The edge of the ice moves further south and so do the walruses. Then in the spring as the weather warms and the ice retreats back up north the walruses follow (Walker, 1975). These huge animals need the ice as resting grounds as well as a source of warmth. The entire herd will haul out together and all lay very close to one another, often on top of each other, to use body heat to warm themselves. This is known as thigmotaxis (Riedman, 1990). At the same time, walruses need constant access to the water. When traveling for long distances it is much less tiring for these huge animals to swim rather than to haul themselves around on the ice. The water is also their primary source for food.

At one time, it was believed that the tusks were used to find their food. It is now known that this is not true. Most tusks observed show wear primarily on the frontal surface. The Walrus seem to glide along the bottom, using its tusks as sled runners, while using its whiskers or vibrissae to search along in the mud for their food (Haley, 1986). The tusks are used for many different things such as hooking over ice for stability while sleeping, to help pull their body out of the water, cutting through ice, and in emergencies of various kinds. A female was once observed totally demolishing a huge, heavy piece of ice just to free her calf, which had fallen into a crevasse (Alaska Dept., 1997). The tusks are important for social display and for fighting. When an individual comes out of the water and seeks a resting spot which is occupied by a smaller animal, it will throw back its head and point its tusks at the smaller walrus (Carling, 1997). The purpose of this type of behavior is to show off their tusk size and to try to scare the other walrus. If this does not scare the smaller one, the larger walrus will actually strike the other with their tusks. This behavior known as tusking is even done when they are young, when calves are interacting with other calves. The walrus with the largest tusks and body size is usually dominant over the others, while the ones with smaller tusks will usually not interfere and move away.

Walruses are very thigmotactic and gregarious and will often fight for space. Walruses seem to prefer to lie in the middle of their large group. The only serious battles, which can become quite brutal, are between walruses of the same body and tusk size. Occasionally males engage in physical combat while trying to hold onto their position with the females (Carling, 1997). They will injure each other by stabbing their tusks into the neck region of the other. These fights generally do not last long and usually end with one bull leaving the area.

When a walrus is foraging for food, instead of using their tusks, they use their whiskers, or "vibrissae." Walruses are better adapted for bottom-feeding than any other pinniped (Oliver 1985). They feed upon invertebrates such as mussels, snails, some crabs, but mainly clams (Carling, 1997). The dives usually last about ten minutes and can reach depths of 10-50 meters. Their vibrissae are just like hundreds of little fingers feeling along in the mud. They also will blow jets of water to loosen clams stuck in the mud (Bering Land, 1995). The soft-bodied organisms are swallowed whole and it used to be believed that hard-shelled organisms were also swallowed whole. It is now known that the fleshy part is actually sucked out of the shell (Carling, 1997). The mouth is specially designed for this purpose. The mouth is narrow with an unusually high roof and strong thick lips. They have a thick piston – like tongue which works with the unique structure of the mouth to produce suction much like a vacuum cleaner (Alaska Dept., 1997). The walrus will hold the organism in its lips and ingest the fleshy part and then discard the shell. They also prey on fish, seals, and some small whales. They are capable of holding down seals and small whales with their fore flippers and tearing them apart with their tusks (Carling, 1997). During the winter, while going through all the courtship behaviors, the males eat very little.

Sexual maturity varies between male and female walruses. Male walruses reach their sexual maturity between the ages of six to ten years old. Females reach maturity at about five to six years old. Both sexes are able to successfully reproduce about five years after they sexually mature. Males, for example, are somewhere around 15 years old before they have their full physical growth and can compete for the females (Sea World, 1994).

Mating season occurs in the mid-winter (December through May). The walruses concentrate in herds. The herds are usually composed of females, calves, and young adults of both sexes (these are ones that haven’t reached sexual maturity). Herds consist of about 12 to 25 walruses. Mating occurs as the walruses are migrating south. The male follows the females south displaying a visual and vocal courtship from the water (Sjare, 1991).

The mating song demonstrated by the males is one of the most complex of all marine mammals, comparable even to that of the Humpback whale. The song consists of knocking (which sounds like knuckles being rapped slowly on a wooden surface), tapping (which is not as loud but faster than knocking) and a ringing bell-like sound. Exactly how the sounds are made is unclear. At one time researchers thought that the knocking and tapping sounds were made with their teeth- however, no signs of wear have been observed. Another possibility is that since they’re capable of sucking clams out of their shells, that they use the same sucking power to produce knocks with their tongues much like humans "cluck" (Sjare, 1991). Males also have two pharyngeal pouches in their upper necks which can be inflated to the size of a basketball. This is where it is believed that the ringing bell-like sound resonates.

These songs are loud enough to be heard up to ten miles away and are rather lengthy. One male was recorded continuously for fifty-five hours (Sjare, 1991). The singing walrus does surface for air about every seven minutes. The songs are very consistent with few changes in their sequence. The songs are so predictable that researchers can use the song to estimate when a male will resurface or dive again. The song is the same for the entire subspecies. Each individual may vary a phrase or two but does it with consistency. Researchers have been able to identify specific individual males throughout an entire mating season solely by their variation of the song (Sjare, 1991).

Males are not the only ones capable of vocalizing, although females lack the pharyngeal pouches that males have, they are able to produce grunts and barks. Calves have been reported bellowing when they were disturbed (Seaworld, 1994).

A male displays these vocalizations to about 23 females during the courtship. The author's have not found any clearly stated research on how many males actually accompany the females during the courtship. The courtship is performed above and below the surface of the water, and the male maintains a distance of seven to ten meters, from the females. The males will fight viciously over the females, with any other intruding male. Once the male is successful with the courtship, the females leave the ice to join the males in the water; this is when copulation occurs (Texas Marine, 1998). The male will then return to the all-male herd and the female begins her gestation period.

The females have a total gestation period of 15 to 16 months, which ensures the calf will be born in optimal environmental conditions to survive. A period of delayed implantation ensures the timing of birth.. Females give birth every two to three years, during April, May, and June, to one young (U.S. Fish and Wildlife Service). There has been a report of twins, but it is rare. The young are born out on the ice (Texas Marine, 1998).

The care of the young is an important role to the walruses. The young are never completely left alone. The females are solely responsible for the protection, and the males hunt for the food (Riedman, 1990). Mothers defend calves, by placing them under their chest between their fore flippers. The calves will often ride on their mother's back in the water if they start to become tired (Reeves, 1992). At birth, calves are about three to four feet long and weigh about 99-165 pounds. These newborn calves are a gray to brown color with short soft fur. The calf becomes more robust within days to weeks. Their fur then turns a reddish-brown to a tan color within one to two weeks. Calves will shed and replace their fur around one or two months old. Then the calves will molt annually (Reeves, 1992). A calf grows about four to six inches in length each month. At one month of age, calves are strong swimmers. Calves will nurse up to two years; sometimes longer if the female doesn’t get pregnant again. Nursing usually takes place in the water (Smithsonian Institution, 1997). The calves rely primarily on milk as their main source of food, even though they occasionally receive solid pieces of food. Cows with newborn calf’s form into their own herds called "nursery herds." These include 20 to 50 individuals and up to 200 walruses.

A pregnant female and her calf, from a previous pregnancy, separate in late April. Male calves may stay an additional two-three years before joining an all-male herd. Female calves stay with the same herd.

Walruses have been exploited for a long time by humans. Many native settlements have been and are located near walrus migration routes. The Natives and Eskimos harvested the walruses for meat, skin, and their ivory tusks. Now through the Marine Mammal Protection Act (MMPA) the walrus is protected, but this still allows Eskimos and Native Alaskans to hunt since the hunting has been a part of their culture (Texas Marine, 1998). Hopefully, educating more people about walruses will help people to see the wonders of this marine mammal.

Alaska Dept. of Fish and Game. "Walrus." Http://www.state.ak.us/local/akpages/FISH.GAME/notebook/marine/walrus.htm. (January, 1997).

Bering Land Bridge National Preserver. "Pacific Walrus." http://www.nps.gov/bela/html/walrus.htm (December,1995).

Carling, M. University of Michigan. "Odobenus rosmarus, Walrus." http://www.o:t.itd.umich.edu/bio/doc.cgi/…arnivora/odobenidae/odobenus_rosmarus.ftl. November, 1997).

Haley D. (1986) 2nd Edition. Marine Mammals, Walrus. Pacific Search Press.

Oliver, JS., Kuitek, Slattery. (1985). Walrus feeding disturbance: scavenging habitats and recolonization of the Bering Sea benthos. J. Exp. Mar. Biol. Ecol.

Reeves,R.R.,Stewart,B.S., Leatherwood,S. (1992). The Sierra Club Handbook of Seals And Sirenians. San Francisco: Sierra Club Books.

Riedman, Marianne (1990). The Pinnipeds; Seals ,Sea Lions, and Walruses. Oxford, England: University of California Press, Ltd.

 Sea Lions, Seals, and Walruses. "walrus." http://www.well.com/user/bridge/sealions_147. Html (1996).

 SeaWorld. "walrus." http://www.seaworld.org.html (1997).

 Sjare, B., Stirling, I. I hear you knocking. Natural History. (March,1991).

 Smithsonian Institution. "walrus Odobenus rosmarus." http://nmnhwww.si.edu/arctic/html/walrus.html (1997).

 Texas Marine Mammal Stranding Network. "walrus (Odobenus rosmarus)." Species Corner:Walrus. http://www.tmmsn.org/mmgulf/odol (1998).

 U.S. Fish & Wildlife Service. "walrus, (Odobenus rosmarus)." Wildlife Species Information. http://www.fws.gov/r9extaff/biologves/bio_walr.html

 Walker, E. (1975). Mammals of the World. Baltimore: The John Hopkins University Press.

 Wildsanctuary. "walrus." http://www.wildsanctuary.com/tooth.html

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