Ear-flaps Collect Sound Waves

photograph of a jaguar laying down on a rock

Biological Strategy

Mammals

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Sense Sound and Other Vibrations From the Environment

For living systems, sensing sound and other vibrations is important for communicating and detecting conditions within their environment. Living systems must locate a signal’s source so that they can move toward it (such as when it is food or a potential mate) or away from it (such as when it is a predator). To prompt an appropriate response, living systems must sense these signals, recognize their amplitude or volume (which is sometimes very low), and determine their direction. Living systems must be attuned to signals relevant to them and able to distinguish these from irrelevant sounds to avoid expending unnecessary energy. For example, owls’ ears are asymmetrically placed. This enables them to detect sounds more accurately, which helps them locate small prey at night and avoid wasting energy chasing down irrelevant sounds.

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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.

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The external ear-flaps of many mammals aid hearing by collecting and concentrating sound waves.

Image: Noodle snacks / Wikimedia commons /

European Rabbit (Oryctolagus cuniculus) in Austins Ferry, Tasmania, Australia

Image: S. Taheri / Wikimedia commons /

Siberian tiger

Image: Malene Thyssen / Wikimedia commons /

Red fox. Picture from Skandinavisk Dyrepark, Denmark

“It is only among mammals that ears become noticeable, even striking, because of the visible external ear-flaps behind the narrow opening of the outer ear tube…The most obvious use of the ear-flap, though not necessarily the most important, is to gather and concentrate sound waves.” (Foy and Oxford Scientific Films 1982:167)

Foy S, Oxford Scientific Films. The Grand Design: Form and Colour in Animals. Lingfield, Surrey, U.K.: BLA Publishing Limited for J. M. Dent & Sons Ltd, London; 1982. 238 p.

“Sound energy spreads out from its sources. For a point source of sound, it spreads out according to the inverse square law. For a given sound intensity, a larger ear captures more of the wave and hence more sound energy. The outer ear structures act as part of the ear’s preamplifier to enhance the sensitivity of hearing.” (R. Nave, HyperPhysics from Georgia State University)

Last Updated September 14, 2016

References

Book

The grand design: Form and colour in animals

BLA Publishing Limited for J.M.Dent & Sons Ltd, Aldine House, London | January 1, 1970 | Sally Foy

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