Difference between revisions of "Walrus" - New World Encyclopedia

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{{Taxobox
 
{{Taxobox
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| image = Walrus.jpg
 
| image = Walrus.jpg
 
| image_width = 250px
 
| image_width = 250px
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| image_caption = The Pacific Walrus
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| image_caption = Pacific Walrus
 
| regnum = [[Animal]]ia
 
| regnum = [[Animal]]ia
 
| phylum = [[Chordate|Chordata]]
 
| phylum = [[Chordate|Chordata]]
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| ordo = [[Carnivora]]
 
| ordo = [[Carnivora]]
 
| subordo = [[Caniformia]]
 
| subordo = [[Caniformia]]
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| superfamilia = [[Pinnipedia]]
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| superfamilia = [[Pinniped]]ia
 
| familia = '''Odobenidae'''
 
| familia = '''Odobenidae'''
 
| familia_authority = Allen, 1880
 
| familia_authority = Allen, 1880
 
| genus = '''''Odobenus'''''
 
| genus = '''''Odobenus'''''
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| genus_authority = [[Mathurin Jacques Brisson|Brisson]]*, 1762
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| genus_authority = [[Mathurin Jacques Brisson|Brisson]], 1762
 
| species = '''''O. rosmarus'''''
 
| species = '''''O. rosmarus'''''
 
| binomial = ''Odobenus rosmarus''
 
| binomial = ''Odobenus rosmarus''
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}}
 
}}
  
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'''Walruses''' are large, marine [[mammal]]s that live in the cold [[Arctic]] seas of the Northern Hemisphere and are the only non-[[seal]]s among the [[pinniped]]s (Pinnipedia). There is only one extant (living) species of walrus, '''Odobenus rosmarus''', which is typically placed in its own pinniped family Odobenidae, although some classifications place walruses in the family Phocidae with the true (earless) seals (McKenna and Bell 1997, Tree of Life Web Project 2000). Like other pinnipeds, walruses have both front and hind limbs in the form of flippers and are unique among marine mammals in needing to come on land (or ice) to breed and raise their offspring.
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The '''walrus''' is a large, semi-aquatic [[mammal]] that lives in the cold [[Arctic]] seas of the Northern Hemisphere and is the only non-[[seal]] [[pinniped]] (Pinnipedia) and the only pinniped with tusks. There is only one extant (living) species of walrus, '''Odobenus rosmarus''', which is typically placed in its own pinniped family '''Odobenidae''', although some classifications place walruses in the family Phocidae with the true (earless) seals (McKenna and Bell 1997, Tree of Life Web Project 2000). Like other pinnipeds, walruses have both front and hind limbs in the form of flippers and need to come on land (or ice) to give birth and raise their offspring.
  
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There are 6 populations of walruses in the arctic and 2 or 3 subspecies exist. Four populations are in the Atlantic, of the subspecies ''Odobenus rosmarus rosmarus'', one is in the Pacific, ''Odobenus r. divergens',' and some consider the sixth population in the Laptev Sea to be a third subspecies, ''Odobenus r. laptevi''. The Pacific walrus is slightly larger, with males weighing up to 1,900 kg (4,180 lb), but Atlantic males top out at 1,600 kg (3,500 lb).  
+
There are six populations of walruses in the arctic and two or three subspecies exist. Four populations are in the Atlantic, of the subspecies ''Odobenus rosmarus rosmarus'', one is in the Pacific, ''Odobenus r. divergens'', and some consider the sixth population in the Laptev Sea to be a third subspecies, ''Odobenus r. laptevi''. The Pacific walrus is slightly larger, with males weighing up to 1,900 kilograms (4,180 pounds), but Atlantic males top out at 1,600 kilograms (3,500 pounds).  
  
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The name walrus comes from Dutch ''walrus'', probably a folk-etymological alteration, via Dutch ''walvis'', "whale," and ''ros'', "horse"—of an older Scandinavian word related to Old Norse ''rosmhvalr'', "red? whale" or "walrus." The compound ''Odobenus'' comes from ''odous'' (Greek for "tooth") and ''baino'' (Greek for "walk"), based on observations of walruses using their tusks to pull themselves out of the water. ''Divergens'' (the Pacific subspecies) in Latin means "turning apart," referring to the tusks.  
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With their plump body, bushy mustache, and peacefully sleepy expression, walruses are often depicted in Western cultural fiction as a happy, lovable, friendly animals, and at times comical. However, they play key roles in [[food chain]]s, consuming [[crustacean]]s, [[fish]], [[mollusk]]s, [[echinoderm]]s, and even [[seal]]s and young [[whale]]s, and being consumed by [[bear]]s, orcas, and humans. Walruses have been utilized by indigenous people for thousands of years, being hunted for their meat, tusks, and skins.
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The name walrus comes from Dutch, ''walrus'', probably a folk-etymological alteration, via Dutch ''walvis'', "whale," and ''ros'', "horse"—of an older [[Scandinavia]]n word related to Old Norse ''rosmhvalr'', "red? whale" or "walrus." The compound ''Odobenus'' comes from ''odous'' (Greek for "tooth") and ''baino'' (Greek for "walk"), based on observations of walruses using their tusks to pull themselves out of the water. ''Divergens'' (the Pacific subspecies) in Latin means "turning apart," referring to the tusks.  
  
 
The walrus should not be confused with the [[seal|elephant seal]], another large [[pinniped]], and despite the etymology of its name it is not related to the [[whale]]s.
 
The walrus should not be confused with the [[seal|elephant seal]], another large [[pinniped]], and despite the etymology of its name it is not related to the [[whale]]s.
  
 +
==Description ==
 +
Walruses are the only pinnipeds that have tusks, which can grow up to one meter in length. Both male and female walruses have tusks, with larger tusks generally among the males. Both males and females also have bristles around the mouth that form a moustache. The Pacific walruses can have longer tusks and smaller noses than the Atlantic populations.
  
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==Lifestyle and feeding==
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Walruses have thick [[skin]], which can get to five centimeters (two inches) thick around the neck and shoulders of males. The underlying blubber may reach 15 centimeters.  
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Walruses spend about half their time in the water and half their time  beaches or ice floes, where they gather in large herds. They may spend several days at a time either on land or in the sea. Diving to depths of 90 m (300 ft), they sometimes stay under for as long as a half hour. They use their [[pectoral]] flippers to move along out of water and can stand on all fours with an awkward gait when on rough surfaces.  
 
  
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In the sea they sometimes catch fish, but generally graze along the sea bottom for clams which they suck from the shell. Pacific walruses feed on more than 60 genera of marine organisms including shrimp, crabs, [[tube worms]], soft coral, [[tunicates]], [[sea cucumbers]], various [[mollusks]], and even parts of other [[pinnipeds]]. Abrasion patterns of the tusks show that the tusks are dragged through the sediment but are not used to dig up prey and the upper edge of the snout is used instead.  Walruses can also spit jets of water to look for clams. Clams and mollusks frequently form the large part of their diet.  Large male walruses have been observed to attack seals if they cannot find any other food source.
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The walruses live around 50 years.  
  
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Walruses have only three natural enemies: humans, [[orca]], and the [[polar bear]]. Polar bears hunt walruses by rushing at them, trying to get the herd to flee, then picking off calves or other stragglers. Walruses have been known to kill polar bears.  
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Walruses spend about half their time in the [[water]] and half their time on [[beach]]es or ice floes, where they gather in large herds. They may spend several days at a time either on land or in the sea. Diving to depths of 90 meters (300 feet), they sometimes stay under for as long as a half hour. They use their pectoral flippers to move along out of water and can stand on all fours with an awkward gait when on rough surfaces.  
  
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The walruses use their long tusks (elongated [[tooth|canines]]) for fighting, dominance, and display and the males will spar with their tusks. They can also use them to form and maintain holes in the ice, or to anchor themselves with the ice.
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In the sea, walruses sometimes catch [[fish]], but generally graze along the sea bottom for [[clam]]s, which they suck from the shell. Pacific walruses feed on more than 60 genera of marine organisms including [[shrimp]], [[crab]]s, [[tube worm]]s, soft [[coral]], [[tunicate]]s, [[sea cucumber]]s and other [[echinoderm]]s, various [[mollusk]]s, and even parts of other [[pinniped]]s. Abrasion patterns of the tusks show that the tusks are dragged through the sediment but are not used to dig up prey and the upper edge of the snout is used instead. Walruses can also spit jets of water to look for clams. Clams and mollusks frequently form the large part of their diet. Large male walruses have been observed to attack [[seal]]s if they cannot find any other food source.
  
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==Physical description and life cycle==
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Walruses have only three natural enemies: [[human being|humans]], [[orca]], and the [[polar bear]]. Polar bears hunt walruses by rushing at them, trying to get the herd to flee, then picking off calves or other stragglers. Walruses have been known to kill polar bears and small whales.
  
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Walruses have thick skin and it can get to 5cm (2in) thick around the neck and shoulders of males. The walruses live around 50 years.
+
The walruses use their long tusks (elongated [[tooth|canines]]) for fighting, dominance, and display and the males will spar with their tusks. They can also use them to form and maintain holes in the ice, or to anchor themselves with the ice.
  
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The males reach sexual maturity around 10 years yet some as early as 7. They go into rut in January thru April, increasing their food intake before the rut, yet then decreasing their food intake dramatically and eating only sporadically during the rut. The females can begin ovulating as soon as 4–6 years old. Interestingly the females are polyestrous, coming into heat in late summer and also around February, yet the males are only fertile around February so the animals are in practicality monoestrous. It is unclear why the females have this second season of potential fertility. By ten years old the females have reached maximum size and all are fertile by then. They breed in January to March with peak conception in February, and perhaps have a [[delayed implantation]] for a few months (4-5) with total [[gestation]] lasting 15–16 months. Walruses mate in the water and give birth on land or ice floes. The males show off in the water for the females who view them from pack ice. Males compete with each other aggressively for this display-space; the winners in these fights breed with large numbers of females. Older male walruses frequently bear large scars from these bloody but rarely fatal battles.
+
The taxonomic group to which walruses and [[seal]]s belong, Pinnipedia, has traditionally been seen as a suborder of the order [[Carnivora]], but more recently is placed as a superfamily within the suborder Caniformia (doglike carnivores); some systematists consider Pinnipedia to be a separate order.
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When a calf is born, it is over 1 m (3 ft) long and able to swim. The calves are born on the pack ice generally April to June and then generally nurse for 8–11 months before they begin eating fish on their own and can spend 3 to 5 years with the mothers.  
 
  
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===Pacific===
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==Life cycle==
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About 200,000 Pacific walruses exist.  Pacific walruses spend the summer north of the [[Bering Strait]] in the [[Chukchi Sea]] along the north shore of eastern [[Siberia]], around [[Wrangel Island]], in the [[Beaufort Sea]] along the north shore of [[Alaska]], and in the waters between those locations. Smaller numbers of males summer in the [[Gulf of Anadyr]] on the south shore of the [[Chukchi Peninsula]] of Siberia and in Bristol Bay off the south shore of southern Alaska west of the [[Alaska Peninsula]]. In the spring and fall they congregate in the Bering Strait, adjacent to the west shores of Alaska, and in the Gulf of Anadyr. They winter to the south in the Bering Sea along the eastern shore of Siberia south to the northern part of the [[Kamchatka Peninsula]], and along the southern shore of Alaska. The Pacific walruses can have longer tusks and smaller noses.
+
The males reach sexual maturity around ten years, although some do so as early as seven. They go into rut in January through April, increasing their food intake before the rut, but decreasing their food intake dramatically and eating only sporadically during the rut.  
  
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===Atlantic===
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Females can begin ovulating as soon as four to six years old. Interestingly, the females are polyestrous, coming into heat both in late summer and also around February, yet the males are only fertile around February so the animals are in practicality monoestrous. It is unclear why the females have this second season of potential fertility. By ten years old, the females have reached maximum size and all are fertile by then.  
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About 15,000 Atlantic walruses exist: they live in the Canadian Arctic, in the waters of [[Greenland]], of [[Svalbard]] and of the western portion of the Russian Arctic. The Atlantic walrus once enjoyed a range that extended south to [[Cape Cod]] and occurred in large numbers in the [[Gulf of St. Lawrence]].
 
  
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==Traditional hunting==
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Breeding takes place from January to March with peak conception in February, and perhaps have a delayed implantation for a few months (four to five) with total gestation lasting 15–16 months. Walruses mate in the water and give birth on land or ice floes. The males show off in the water for the females who view them from pack ice. Males compete with each other aggressively for this display space; the winners in these fights breed with large numbers of females. Older male walruses frequently bear large scars from these bloody but rarely fatal battles.
  
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[[Alaska Natives]] slaughter about 3,000 walruses annually. Humans use ivory from the tusks for carving. The natives call the [[penis bone]] of male an ''[[oosik]]'' and use it in making knives.
+
When a calf is born, it is over one meter (three feet) long and able to swim. The calves are born on the pack ice generally April to June and then generally nurse for 8–11 months before they begin eating fish on their own. They can spend three to five years with the mothers.  
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Federal laws in both the USA and in Canada protect walruses and set quotas on the yearly harvest. Only under rare circumstances may non-native hunters gain permission to kill a walrus legally.  The law prohibits the export of raw tusks from Alaska, but walrus-ivory products may come on the market if first sculpted into [[scrimshaw]] by a native craftsman.  Commercial auction sites such as [[eBay]] make a large selection of "pre-ban" wal available.
 
  
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==Medical problems==
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==Distribution==
 +
About 200,000 Pacific walruses exist. Pacific walruses spend the summer north of the [[Bering Strait]] in the Chukchi Sea along the north shore of eastern [[Siberia]]; around Wrangel Island in the [[Arctic Ocean]]; in the Beaufort Sea along the north shore of [[Alaska]]; and in the waters between those locations. Smaller numbers of males summer in the [[Gulf of Anadyr]] on the south shore of the Chukchi Peninsula of Siberia and in Bristol Bay off the south shore of southern Alaska west of the Alaska Peninsula.
  
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Eye problems for the walrus are common and they sometimes experience intestinal disease. They sometimes get tusk infections, and in captivity are prone to ingesting foreign objects. Also various common fungal and bacterial sometimes cause minor infections. Trampling and tusk injuries occur during interactions and sometimes females are harassed and show bruises and laceration.  
+
In the spring and fall, Pacific walruses congregate in the Bering Strait, adjacent to the west shores of Alaska, and in the Gulf of Anadyr. They winter to the south in the Bering Sea along the eastern shore of Siberia south to the northern part of the [[Kamchatka Peninsula]], and along the southern shore of Alaska.  
  
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The atlantic walruses show exposure to the bacteria [[Brucella]] and sometimes will show infection with [[Trichinella]] and also lice. [[Calicivirus]]es are thought to sometimes affect Pacific walruses causing skin lesions and they are thought to have a wide exposure to the viruses. These viruses are thought to interact between terrestrial and aquatic mammals, with marine mammals showing antibodies to many caliciviruses that affect land mammals. [[Herpesvirus]]es can also be seen sometimes in the walrus population.  
+
About 15,000 Atlantic walruses exist: they live in the Canadian Arctic; in the waters of [[Greenland]]; off of Svalbard in the Arctic Ocean, north of mainland [[Europe]]; and off of the western portion of the Russian Arctic. The Atlantic walrus once enjoyed a range that extended south to Cape Cod and occurred in large numbers in the Gulf of St. Lawrence.
  
 +
==Traditional hunting==
  
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==The walrus in popular culture==
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Alaska Natives slaughter about three thousand walruses annually. Humans use [[ivory]] from the tusks for carving. The natives call the penis bone of males an ''oosik'' and use it in making knives. Although a male walrus's penis is completely internal, it has one of the largest bacula (penis bones) of the animal kingdom.
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In [[western culture]], fiction often depicts the species—with its plump body, bushy mustache, and peacefully sleepy expression—as a happy, lovable and friendly animal, and its appearance may be interpreted as somewhat comical.
 
  
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===In literature and music===
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Federal laws in both the [[United States]] and in [[Canada]] protect walruses and set quotas on the yearly harvest. Only under rare circumstances may non-native hunters gain permission to kill a walrus legally. The law prohibits the export of raw tusks from Alaska, but walrus ivory products may come on the market if first sculpted into scrimshaw by a native craftsman.
  
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*[[Farley Mowat]]'s book ''[[Sea of Slaughter]]'' has a large section dedicated to the effects of hunting on eastern Canada's walrus population.
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==Medical problems==
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*[[Lewis Carroll]]'s famous [[poem]] "[[The Walrus and the Carpenter]]" inspired the 1967 song "[[I Am the Walrus]]" by [[The Beatles]]. In the song [[John Lennon]] is "the Walrus". However, in order to deliberately confuse his fans, Lennon sings in the later song "[[Glass Onion]]" that "the Walrus was Paul". In the solo song "God," Lennon sings "I was the Walrus, but now, I'm John."
 
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*''[[The Walrus]]'' is a Canadian news magazine.
 
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*In [[Salman Rushdie]]'s children's book ''[[Haroun and the Sea of Stories]]'', The Walrus is the name of the imposing Grand Controller of Gup.
 
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*''Walrus'' is also the name of Captain Flint's ship in [[Robert Louis Stevenson]]'s ''[[Treasure Island]]''.
 
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*[[Sam Allardyce]], the manager of English football team [[Bolton Wanderers]] is often nicknamed Walrus, due to his uncanny physical resemblance to the creature.
 
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*[[Antti Muurinen]], the former manager of Finnish football national side is nicknamed Walrus by Finnish football enthusiasts.
 
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===In other media===
 
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The Walrus is a very commonly seen animal in [[animation]]. They are usually portrayed as rugged but experienced and lovable characters, or as aristocratic characters due to the animal's snout looking somewhat like a mustache.
 
  
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*'''[[Rotor (Sonic the Hedgehog)|Rotor]] the Walrus''', a.k.a "Boomer", is a prominent character in ''[[SatAM]]'' ''[[Sonic the Hedgehog series|Sonic the Hedgehog]]'' animated series as well as the ongoing ''[[Sonic the Hedgehog (Archie comic)|Sonic the Hedgehog]]'' [[comic book]] [[continuity (fiction)|continuity]]. Rotor is the protagonist group's brave but shy mechanical super-genius and intellectual. He is very friendly and generally fits the archetypal personality of the walrus.
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[[Eye]] problems for the walrus are common and they sometimes experience intestinal [[disease]]. They sometimes get tusk infections, and in captivity they are prone to ingesting foreign objects. Also various [[fungus]] and [[bacteria]] sometimes cause minor infections. Trampling and tusk injuries occur during interactions and sometimes females are harassed and show bruises and laceration.  
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*The '''Captain of the Thames''' is an anthropomorphic walrus from the [[video game]] ''[[Xenogears]]''. He is a demi-human, captain, and all around man of the sea.
 
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*'''Frost Walrus''' is one of the Maverick bosses in the video game ''[[Mega Man X4]]''.
 
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*'''[[EverQuest]]''' has many walruses in the world of Norrath.
 
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*'''Chumley''' is the sidekick of the title character in the cartoon series ''[[Tennessee Tuxedo and His Tales]]''. He is good natured if a bit dim.
 
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*'''Wally Walrus''' is a character from the ''[[Woody Woodpecker]]'' cartoons. He was the nemesis as well as rival of the title character.
 
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*'''''Cardo/Willin''''' is an ex character from an old internet French show called MainFrame
 
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*'''The King of the World''' is an occasionally seen character from the various ''[[Dragon Ball]]'' [[anime]] series. Although not stated, he is an odd mix of a walrus and a dog.
 
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*'''McSweeny''', a large and muscular walrus, is a very minor character from the ''[[Sly Cooper]]'' series of video games.
 
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*'''The Walrus''' is an offbeat, silly, and obscure character from various [[Marvel Comics]].
 
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*'''Bletch''' is the name of the walrus of the film by director [[Peter Jackson]], ''[[Meet The Feebles]]''. Unlike the passive image of walruses, Bletch is very mean and cheats on his hippopotamus lover with a cat.
 
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*'''Wendell''' is the starving walrus in the ''[[Animal Crossing (series)|Animal Crossing]]'' video game series.
 
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*'''Wozza the Walrus''' is a walrus from [[Banjo-Kazooie]] who lives in Freezeezy Peak inside a cave.
 
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*'''PGA tour Champion Craig Stadler''' is nicknamed the Walrus.
 
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*'''Tuskernini''' is an anthropomorphic walrus villain on the [[Darkwing Duck]] cartoon.
 
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*'''Jocco''' is the walrus pal to Henry in the movie ''[[50 First Dates]]''.
 
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*'''Tusky''' is [[Aquaman]]'s pet in [[The Superman/Aquaman Hour of Adventure]] cartoons.
 
  
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==Trivia==
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The Atlantic walruses show exposure to the bacteria ''Brucella'' and sometimes will show infection with ''Trichinella'' and also lice. Caliciviruses are thought to sometimes affect Pacific walruses causing skin lesions and they are thought to have a wide exposure to the [[virus]]es. These viruses are thought to interact between terrestrial and aquatic mammals, with marine mammals showing [[antibody|antibodies]] to many caliciviruses that affect land mammals. [[Herpesvirus]]es can also be seen sometimes in the walrus population.
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*[[Savoonga, Alaska]] calls itself the "Walrus Capital of the World".
 
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* Walruses are among the only mammals in the world that do not process liquid waste via a [[bladder]] organ. Once digested, liquid waste is absorbed through the lining of the [[small intestine]] and secreted through the [[skin]].
 
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*A male walrus's penis is completely internal, however it has one of the largest [[baculum|bacula]] (penis bones) of the animal kingdom.
 
  
 
==References==
 
==References==
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* {{IUCN2006|assessors=Seal Specialist Group|year=1996|id=15106|title=Odobenus rosmarus|downloaded=12 May 2006}}
 
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* Marine Mammal Medicine, Leslie Dierauf and Frances Gulland, CRC Press 2001, ISBN 0-8493-0839-9
 
  
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* Flynn, J., J. Finarelli, S. Zehr, J. Hsu, and M. Nedbal. 2005. [http://home.uchicago.edu/~johnf/pdf/Flynn_etal_2005.pdf Molecular phylogeny of the Carnivora (Mammalia): Assessing the impact of increased sampling on resolving enigmatic relationships]. ''Systematic Biology'' 54(2):317-337.
+
* Dierauf, L., and F. Gulland. 2001. ''Marine Mammal Medicine''. CRC Press. ISBN 0849308399
 +
* Flynn, J., J. Finarelli, S. Zehr, J. Hsu, and M. Nedbal. 2005. “Molecular phylogeny of the Carnivora (Mammalia): Assessing the impact of increased sampling on resolving enigmatic relationships.” ''Systematic Biology'' 54(2): 317-337. Retrieved August 27, 2007.
 
* McKenna, M. C., and S. K. Bell. 1997. ''Classification of Mammals Above the Species Level''. New York: Columbia University Press.
 
* McKenna, M. C., and S. K. Bell. 1997. ''Classification of Mammals Above the Species Level''. New York: Columbia University Press.
−
* Myers, P., and A. Poor. 2007. [http://animaldiversity.ummz.umich.edu/site/accounts/information/Carnivora.html Carnivora]. ''Animal Diversity Web''. Accessed January 23, 2007.
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* Myers, P., and A. Poor. 2007. [http://animaldiversity.ummz.umich.edu/site/accounts/information/Carnivora.html Carnivora]. Animal Diversity Web. Accessed August 27, 2007.
−
* Nowak, R. M. 1999. ''Walker's Mammals of the World'', 6th Edition. Baltimore: The John's Hopkins Press.
+
* Nowak, R. M. 1999. ''Walker's Mammals of the World'', 6th ed. Baltimore, MD: The Johns Hopkins University Press. ISBN 0801857899
−
* Riedman, M. 1990. [http://polarmet.mps.ohio-state.edu/ASPIRE_99/seals/science/evxt.htm ''Pinnipeds: Seals, Sea Lions, and Walruses'']. Berkeley: University of California Press.  
+
* Seal Specialist Group. 1996. [http://www.iucnredlist.org/search/details.php/15106/all ''Odobenus rosmarus'']. In [http://www.iucnredlist.org ''2006 IUCN Red List of Threatened Species''.] Retrieved August 27, 2007.
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* Tree of Life Web Project. 2000. [http://tolweb.org/Carnivora/15971 Carnivora. Dogs, cats, bears, raccoons, weasels, mongooses, hyenas, seals, walruses, etc. Version 01 January 2000]. ''Tree of Life Web Project''. Retrieved January 23, 2007.
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* Tree of Life Web Project. 2000. Carnivora. Dogs, cats, bears, raccoons, weasels, mongooses, hyenas, seals, walruses, etc. Version 01 January 2000. ''Tree of Life Web Project''.  
−
* Wozencraft, W. C. 1992. Order Carnivora. In D. E. Wilson and D. M. Reeder (eds.), ''Mammal Species of the World: A Taxonomic and Geographic Reference'', 2nd. edition. Washington: Smithsonian Institution Press.
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* Wozencraft, W. C. 1992. Order Carnivora. In D. E. Wilson and D. M. Reeder (eds.), ''Mammal Species of the World: A Taxonomic and Geographic Reference'', 2nd ed. Washington, DC: Smithsonian Institution Press.
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[[Category:Pinnipeds]]
 
  
 
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[[Category:Life sciences]]
 
[[Category:Life sciences]]
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[[Category:Mammals]]

Latest revision as of 18:47, 17 April 2023


Walrus
Pacific Walrus
Pacific Walrus
Conservation status
Status iucn3.1 LC.svg
Least Concern
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Caniformia
Superfamily: Pinnipedia
Family: Odobenidae
Allen, 1880
Genus: Odobenus
Brisson, 1762
Species: O. rosmarus
Binomial name
Odobenus rosmarus
(Linnaeus, 1758)
Subspecies

O. rosmarus rosmarus
O. rosmarus divergens

The walrus is a large, semi-aquatic mammal that lives in the cold Arctic seas of the Northern Hemisphere and is the only non-seal pinniped (Pinnipedia) and the only pinniped with tusks. There is only one extant (living) species of walrus, Odobenus rosmarus, which is typically placed in its own pinniped family Odobenidae, although some classifications place walruses in the family Phocidae with the true (earless) seals (McKenna and Bell 1997, Tree of Life Web Project 2000). Like other pinnipeds, walruses have both front and hind limbs in the form of flippers and need to come on land (or ice) to give birth and raise their offspring.

There are six populations of walruses in the arctic and two or three subspecies exist. Four populations are in the Atlantic, of the subspecies Odobenus rosmarus rosmarus, one is in the Pacific, Odobenus r. divergens, and some consider the sixth population in the Laptev Sea to be a third subspecies, Odobenus r. laptevi. The Pacific walrus is slightly larger, with males weighing up to 1,900 kilograms (4,180 pounds), but Atlantic males top out at 1,600 kilograms (3,500 pounds).

With their plump body, bushy mustache, and peacefully sleepy expression, walruses are often depicted in Western cultural fiction as a happy, lovable, friendly animals, and at times comical. However, they play key roles in food chains, consuming crustaceans, fish, mollusks, echinoderms, and even seals and young whales, and being consumed by bears, orcas, and humans. Walruses have been utilized by indigenous people for thousands of years, being hunted for their meat, tusks, and skins.

The name walrus comes from Dutch, walrus, probably a folk-etymological alteration, via Dutch walvis, "whale," and ros, "horse"—of an older Scandinavian word related to Old Norse rosmhvalr, "red? whale" or "walrus." The compound Odobenus comes from odous (Greek for "tooth") and baino (Greek for "walk"), based on observations of walruses using their tusks to pull themselves out of the water. Divergens (the Pacific subspecies) in Latin means "turning apart," referring to the tusks.

The walrus should not be confused with the elephant seal, another large pinniped, and despite the etymology of its name it is not related to the whales.

Description

Walruses are the only pinnipeds that have tusks, which can grow up to one meter in length. Both male and female walruses have tusks, with larger tusks generally among the males. Both males and females also have bristles around the mouth that form a moustache. The Pacific walruses can have longer tusks and smaller noses than the Atlantic populations.

Walruses have thick skin, which can get to five centimeters (two inches) thick around the neck and shoulders of males. The underlying blubber may reach 15 centimeters.

The walruses live around 50 years.

Walruses spend about half their time in the water and half their time on beaches or ice floes, where they gather in large herds. They may spend several days at a time either on land or in the sea. Diving to depths of 90 meters (300 feet), they sometimes stay under for as long as a half hour. They use their pectoral flippers to move along out of water and can stand on all fours with an awkward gait when on rough surfaces.

In the sea, walruses sometimes catch fish, but generally graze along the sea bottom for clams, which they suck from the shell. Pacific walruses feed on more than 60 genera of marine organisms including shrimp, crabs, tube worms, soft coral, tunicates, sea cucumbers and other echinoderms, various mollusks, and even parts of other pinnipeds. Abrasion patterns of the tusks show that the tusks are dragged through the sediment but are not used to dig up prey and the upper edge of the snout is used instead. Walruses can also spit jets of water to look for clams. Clams and mollusks frequently form the large part of their diet. Large male walruses have been observed to attack seals if they cannot find any other food source.

Walruses have only three natural enemies: humans, orca, and the polar bear. Polar bears hunt walruses by rushing at them, trying to get the herd to flee, then picking off calves or other stragglers. Walruses have been known to kill polar bears and small whales.

The walruses use their long tusks (elongated canines) for fighting, dominance, and display and the males will spar with their tusks. They can also use them to form and maintain holes in the ice, or to anchor themselves with the ice.

The taxonomic group to which walruses and seals belong, Pinnipedia, has traditionally been seen as a suborder of the order Carnivora, but more recently is placed as a superfamily within the suborder Caniformia (doglike carnivores); some systematists consider Pinnipedia to be a separate order.

Life cycle

The males reach sexual maturity around ten years, although some do so as early as seven. They go into rut in January through April, increasing their food intake before the rut, but decreasing their food intake dramatically and eating only sporadically during the rut.

Females can begin ovulating as soon as four to six years old. Interestingly, the females are polyestrous, coming into heat both in late summer and also around February, yet the males are only fertile around February so the animals are in practicality monoestrous. It is unclear why the females have this second season of potential fertility. By ten years old, the females have reached maximum size and all are fertile by then.

Breeding takes place from January to March with peak conception in February, and perhaps have a delayed implantation for a few months (four to five) with total gestation lasting 15–16 months. Walruses mate in the water and give birth on land or ice floes. The males show off in the water for the females who view them from pack ice. Males compete with each other aggressively for this display space; the winners in these fights breed with large numbers of females. Older male walruses frequently bear large scars from these bloody but rarely fatal battles.

When a calf is born, it is over one meter (three feet) long and able to swim. The calves are born on the pack ice generally April to June and then generally nurse for 8–11 months before they begin eating fish on their own. They can spend three to five years with the mothers.

Distribution

About 200,000 Pacific walruses exist. Pacific walruses spend the summer north of the Bering Strait in the Chukchi Sea along the north shore of eastern Siberia; around Wrangel Island in the Arctic Ocean; in the Beaufort Sea along the north shore of Alaska; and in the waters between those locations. Smaller numbers of males summer in the Gulf of Anadyr on the south shore of the Chukchi Peninsula of Siberia and in Bristol Bay off the south shore of southern Alaska west of the Alaska Peninsula.

In the spring and fall, Pacific walruses congregate in the Bering Strait, adjacent to the west shores of Alaska, and in the Gulf of Anadyr. They winter to the south in the Bering Sea along the eastern shore of Siberia south to the northern part of the Kamchatka Peninsula, and along the southern shore of Alaska.

About 15,000 Atlantic walruses exist: they live in the Canadian Arctic; in the waters of Greenland; off of Svalbard in the Arctic Ocean, north of mainland Europe; and off of the western portion of the Russian Arctic. The Atlantic walrus once enjoyed a range that extended south to Cape Cod and occurred in large numbers in the Gulf of St. Lawrence.

Traditional hunting

Alaska Natives slaughter about three thousand walruses annually. Humans use ivory from the tusks for carving. The natives call the penis bone of males an oosik and use it in making knives. Although a male walrus's penis is completely internal, it has one of the largest bacula (penis bones) of the animal kingdom.

Federal laws in both the United States and in Canada protect walruses and set quotas on the yearly harvest. Only under rare circumstances may non-native hunters gain permission to kill a walrus legally. The law prohibits the export of raw tusks from Alaska, but walrus ivory products may come on the market if first sculpted into scrimshaw by a native craftsman.

Medical problems

Eye problems for the walrus are common and they sometimes experience intestinal disease. They sometimes get tusk infections, and in captivity they are prone to ingesting foreign objects. Also various fungus and bacteria sometimes cause minor infections. Trampling and tusk injuries occur during interactions and sometimes females are harassed and show bruises and laceration.

The Atlantic walruses show exposure to the bacteria Brucella and sometimes will show infection with Trichinella and also lice. Caliciviruses are thought to sometimes affect Pacific walruses causing skin lesions and they are thought to have a wide exposure to the viruses. These viruses are thought to interact between terrestrial and aquatic mammals, with marine mammals showing antibodies to many caliciviruses that affect land mammals. Herpesviruses can also be seen sometimes in the walrus population.

References
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  • Flynn, J., J. Finarelli, S. Zehr, J. Hsu, and M. Nedbal. 2005. “Molecular phylogeny of the Carnivora (Mammalia): Assessing the impact of increased sampling on resolving enigmatic relationships.” Systematic Biology 54(2): 317-337. Retrieved August 27, 2007.
  • McKenna, M. C., and S. K. Bell. 1997. Classification of Mammals Above the Species Level. New York: Columbia University Press.
  • Myers, P., and A. Poor. 2007. Carnivora. Animal Diversity Web. Accessed August 27, 2007.
  • Nowak, R. M. 1999. Walker's Mammals of the World, 6th ed. Baltimore, MD: The Johns Hopkins University Press. ISBN 0801857899
  • Seal Specialist Group. 1996. Odobenus rosmarus. In 2006 IUCN Red List of Threatened Species. Retrieved August 27, 2007.
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  • Wozencraft, W. C. 1992. Order Carnivora. In D. E. Wilson and D. M. Reeder (eds.), Mammal Species of the World: A Taxonomic and Geographic Reference, 2nd ed. Washington, DC: Smithsonian Institution Press.

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