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Towards a Predator-Prey Model Incorporating Age Structure: The Effects of Predator and Prey Size on the Predation of Daphnia magna by Ischnura elegans

D. J. Thompson
Journal of Animal Ecology
Vol. 44, No. 3 (Oct., 1975), pp. 907-916
DOI: 10.2307/3727
Stable URL: http://www.jstor.org/stable/3727
Page Count: 10
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Towards a Predator-Prey Model Incorporating Age Structure: The Effects of Predator and Prey Size on the Predation of Daphnia magna by Ischnura elegans
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Abstract

(1) The functional responses of five instars of Ischnura elegans feeding on five arbitrary size-classes of Daphnia magna were obtained. (2) The two basic components of predator-prey models, the attack coefficient, a, and the handling time, Th, were estimated from the data using the random predator equation of Rogers (1972). (3) Two ways in which the parameter estimates from the random predator equation may be unrealistic are discussed; they are the use of too many points on the plateau of a type 2 functional response curve in estimating a and Th and the use of data points in which over-exploitation had occurred. (4) The variation of a and Th with prey and predator size is described. Both increase nearly monotonically, a with increased predator size and decreased prey size, Th with decreased predator size and increased prey size. The possible effects of prey and predator size on the sub-components of a and Th are discussed. (5) The consequences of the fact that the a and Th values used are averages over the time the experiment was run are considered.

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