Odobenus rosmarus (Linnaeus, 1758)
Walrus
Species recognized by The Integrated Taxonomic Information System
, T Orrell (custodian) in 
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General Description
Teeth crush shells: walrus
Source and Additional Information
The cheek teeth of walruses are capable of crushing tough shells because they are strong and flat.
"The walrus has only 18 teeth in its mouth, but the upper canines form great ivory tusks up to a metre long. It uses them for levering itself on to ice floes, as weapons in battles with other males over females, and as digging tools to extract clams and other invertebrates from the sea bed. A walrus may dive to depths of 200 metres and more in search of food, and is thought to use its tusks to plough up the sediments on the sea bottom to expose shells, which are recognized in these murky depths by the stiff sensory bristles on its snout. Behind the tusks are strong flat teeth capable of crushing the hardest shells." (Foy and Oxford Scientific Films 1982:147)
Learn more about this functional adaptation.
References
- Foy, Sally; Oxford Scientific Films. 1982. The Grand Design: Form and Colour in Animals. Lingfield, Surrey, U.K.: BLA Publishing Limited for J.M.Dent & Sons Ltd, Aldine House, London. 238 p.
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Tusks conserve materials: walrus
Source and Additional Information
The tusks of a walrus conserve materials because they are multi-functional.
"The walrus has only 18 teeth in its mouth, but the upper canines form great ivory tusks up to a metre long. It uses them for levering itself on to ice floes, as weapons in battles with other males over females, and as digging tools to extract clams and other invertebrates from the sea bed. A walrus may dive to depths of 200 metres and more in search of food, and is thought to use its tusks to plough up the sediments on the sea bottom to expose shells, which are recognized in these murky depths by the stiff sensory bristles on its snout. Behind the tusks are strong flat teeth capable of crushing the hardest shells." (Foy and Oxford Scientific Films 1982:147)
Learn more about this functional adaptation.
References
- Foy, Sally; Oxford Scientific Films. 1982. The Grand Design: Form and Colour in Animals. Lingfield, Surrey, U.K.: BLA Publishing Limited for J.M.Dent & Sons Ltd, Aldine House, London. 238 p.
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Description
Source and Additional Information
Both male and female walruses have tusks, upper canine teeth that continue to grow throughout their lives. Males' tusks are larger and are used for display and as weapons, usually in competition with other males. Walruses occupy the continental shelf rather than deep water, feeding at depths no greater than 100 m. They eat a large variety of bottom-dwelling invertebrates, from tiny crustaceans to octopuses and large crabs. Walruses breed deep in the Arctic pack ice during the darkness of winter. Females begin breeding at 6-7 years of age, and have just one calf after a long, almost 15-month pregnancy. Males are sexually mature at about 9-10 years, but may not be successful in competing for mates until they are about 15 years old. Humans have exploited walruses for years for their ivory tusks, and also for meat, oil, and hides. Their only other predators are polar bears and killer whales, which mostly take the young.
Adaptation: Most parts of the skull of the Walrus, Odobenus rosmarus, have evolved to accommodate the enormous, heavy tusks. This includes not only the facial bones, which root them and basically make up the whole snout, but also the back of the skull, where the prominent flange of bone in the area of the ear is an attachment site for the major muscles that move this massive head around.
Links:
Mammal Species of the World
Click here for The American Society of Mammalogists species account
Adaptation: Most parts of the skull of the Walrus, Odobenus rosmarus, have evolved to accommodate the enormous, heavy tusks. This includes not only the facial bones, which root them and basically make up the whole snout, but also the back of the skull, where the prominent flange of bone in the area of the ear is an attachment site for the major muscles that move this massive head around.
Links:
Mammal Species of the World
Click here for The American Society of Mammalogists species account
References
- Linnaeus, C., 1758. Systema Naturae per regna tria naturae, secundum classis, ordines, genera, species cum characteribus, differentiis, synonymis, locis. p. 38. Tenth Edition, Vol. 1. Laurentii Salvii, Stockholm, 824 pp.
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Last curated:
18 Jun 2009
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Katja Schulz.
Curator.
"Odobenus rosmarus (Linnaeus, 1758)". Encyclopedia of Life, available from "http://www.eol.org/pages/328627". Accessed
19 Mar 2010.
