Doctoral Dissertations

Date of Award

3-1988

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major Professor

Dewey L. Bunting

Abstract

Literature suggests that often predatory interactions cannot be adequately described as random events occurring in time. Factors that could complicate this simple description might be: intervals of no predator behavior associated with predation; digestion or some other behavior associated with predation sufficient to inhibit or prevent more events; predator learning; changed in predator search strategies; prey grouping; changes in prey defensive strategies; environmental heterogeneity; relative predator-prey size differences. Furthermore, it is suggested that Chaoborus spp. (Diptera; Culicidae) predation might be arranged such that only digestion is affecting the underlying random process.

Proportional increases in the average number of prey eaten per predator with increasing prey density are expected from random events in time. The non-proportionality of increases observed with Chaoborus predation is considered the result and confirmation of digestive interference. If digestion affects the average eaten, distributions of individual predator responses at any prey density should likewise show a digestive pause effect.

Female Mesocvcloos edax (Copepoda; Cyclopoida) copepods were counted before and after 6 hours in 880ml filtered lake water with a fourth instar C. punctioennis larva. Missing copepods were assumed eaten by the larva. m

7100+ observations ranging between 3 and 40 introduced prey were analyzed by a single regression of average eaten to prey density. Linear regression showed that a negative quadratic expression provided an adequate fit. A digestive pause estimate of 2.5 ± 1.0 hours per each prey item was provided through non-linear regression.

However, all empirical distributions of this data set were similar to those representing random events in time with no digestive pause; Poisson distributions. When the empirical distributions were compared to stochastically created computer simulations incorporating just 0.5 hours of digestive pause per prey item, statistical differences were detected. It was concluded that some process other than digestion was producing the observed non-proportionality.

It is suggested through elimination of complicating factors that only some form of rudimentary prey grouping, perhaps conceived as trailing, can be responsible for the non-proportionality. If so, it seems that sufficient predation attrition must implant the behavior throughout the prey population.

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