Tusks Are Multifunctional

photograph of a walrus laying down on ice

Biological Strategy

Walrus

AskNature Team

Image: Gregoire Dubois / Flickr / Some rights reserved

Optimize Shape/Materials

Resources are limited and the simple act of retaining them requires resources, especially energy. Living systems must constantly balance the value of resources obtained with the costs of resources expended; failure to do so can result in death or prevent reproduction. Living systems therefore optimize, rather than maximize, resource use. Optimizing shape ultimately optimizes materials and energy. An example of such optimization can be seen in the dolphin’s body shape. It’s streamlined to reduce drag in the water due to an optimal ratio of length to diameter, as well as features on its surface that lie flat, reducing turbulence.

Search this Function

Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

Search this Living System

The tusks of a walrus are tools that have social and mechanical functions.

“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)

Last Updated August 14, 2017

References

“Large tusks (upper canines) occur in both sexes and are used in defence against predators, for breaking through ice, in intraspecific strife, for hooking over the edge of ice for stability while sleeping in the water, and as aids to hauling out and locomotion on ice (Belopolsky 1939; Burns 1965; Chapskii 1936; Collins 1940; Fay, unpublished data; Loughrey 1959; Nikulin 1941,1947; Ognev 1935; Pedersen 1962). It is widely believed that tusks function most importantly in feeding, by digging food out of the sea floor. Detailed studies of feeding ecology and functional anatomy dispel this notion, and suggest that walrus tusks have evolved chiefly for social communication.” (Miller 1975:590)

Journal article

Walrus ethology. I. The social role of tusks and applications of multidimensional scaling

Canadian Journal of Zoology, 53(5): 590-613 | 01/05/1975 | Miller EH

embedly preview

Reference

“The primary role of the tusks probably is a social one…The walrus’ use of its tusks in threat displays (Frontispiece) was formally reported first by Loughrey (1959:48), who observed that an animal with very large tusks can intimidate others “to move out of its way simply by threatening them,” whereas one with smaller tusks is met with active opposition from his peers. Both large tusks and large body size exert positive influence on achievement of a socially dominant position in male walruses (Miller 1975a)” (Fay 1982:135-136)

“Ancillary functions of the tusks include their use as weapons, both offensively and defensively.” (Fay 1982:136)

Journal article

Ecology and Biology of the Pacific Walrus, Odobenus rosmarus divergens Illiger

North American Fauna, 74: 1 – 279 | 01/01/1982 | Fay FH

embedly preview

AskNature