Echolocation: Discrimination of targets by the bat, Eptesicus fuscus


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Publication Date

March 1971


Bats of the species Eptesicus fuscus learned to discriminate differences in the size of targets, the shape of targets, and the distance to targets by means of sonar. Eptesicus can detect differences of as little as 17% in the surface area of triangular targets. Measurements of the echo properties of the targets suggest that the bats used differences in the overall intensity of the echoes to differentiate the larger triangle from the smaller. If so, the smallest detectable echo intensity difference for Eptesicus would be between 1.5 and 3.0 dB. In discriminating a tall, narrow triangle from a short, wide triangle the bats may have scanned the target shapes with the directional beam of their sonar to produce discriminable intensity differences between echoes. Eptesicus can discriminate between targets differing by as little as 12 to 13 mm in distance. If echo travel time is providing the bat with target range information, then the bat evidently can detect echo arrival‐time differences of as little as 70 to 75 μsec. The ability of the bat to discriminate between targets which produce echoes that arrive at the bat's ears overlapping each other for 90 to 100% of their total duration demonstrates the effectiveness of the mechanisms in the bat's sonar for rejecting interference caused by multiple‐target clutter.


Eptesicus Fuscus, Bats, Targets, Discrimination

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Journal of Experimental Zoology, Vol. 176, no. 3 (1971-03).