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The Feeding Efficiency of Insectivorous Bats

Edwin Gould
DOI: http://dx.doi.org/10.2307/1375682 399-407 First published online: 1 August 1955

Griffin (1953) has recently suggested that insectivorous bats use their high frequency sounds not only for avoiding stationary obstacles but also for locating and capturing flying insects. Evaluation of this hypothesis requires accurate information about the sizes and sound reflecting properties of bats' insect prey, and this paper will assemble the pertinent data that I have been able to obtain both from previous papers and from the analysis of many digestive tracts of bats collected for this purpose. In addition to the types of insects captured the rate at which they are taken was measured whenever possible in order to judge whether a process of selective pursuit and capture is involved, or whether a random process akin to “filter feeding” could account for the efficiency actually attained. It would also be desirable to know the distances at which flying insects are detected; but to date no satisfactory methods have been developed for obtaining more than the rough estimate of this quantity included below for the red bat, Lasiurus borealis.

I wish to acknowledge my gratitude for advice received from the following entomologists, who identified many of the insect remains from bat stomachs; Asher Treat, John G. Franclemont, Howard Ensign Evans, W. T. M. Forbes, Clifford 0. Berg, George Ball, Benjamin Henson, and Charles Wyttenbach.

Encouragement and helpful criticism were also provided by Donald R. Griffin. This work was supported financially by contracts between the Office of Naval Research and Cornell University (Zoology Department) and Harvard University (Biological Laboratories).

Data from previous work.—While many studies of bats’ feeding habits have been reported, the results are often useless for the present purpose either because the insects could be identified only to order or family, leaving a considerable range of uncertainty as to their actual sizes, or because the identity of …

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