Predator ingestion rate and its bearing on feeding time and the theory of oprimal diets

Cook, R.M. and Cockrell, B.J. (1978) Predator ingestion rate and its bearing on feeding time and the theory of oprimal diets. Journal of Animal Ecology, 47 (2). pp. 529-547. ISSN 0021-8790

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Abstract

(1) Two insect predators, Adalia bipunctata (L.) and Notonecta glauca (L.) are shown to have ingestion rates which decline over the time whilst the animal is feeding on a single prey item. The decline is not due to satiation. (2) A model which maximizes the average rate of energy harvest is applied to the ingestion curve effect. The length of time spent feeding on a prey item is determined by this average rate and predicts that feeding times will be shorter in more profitable environments. (3) Experiments support the prediction that feeding time per item and the amount of food eaten per item decreases as the intercatch interval shortens. Unlike predictions from a gut limiting hypothesis, feeding times seem to be related to the average intercatch interval not the individual intercatch intervals. (4) The ingestion rate effect is incorporated into an optimal diet model. Prey types should not be ranked by their average profitability but by their unexploited profitability. (5) The modified optimal diet model will predict a variety of functional response curves dependent on the form of the ingestion curve. These include double plateau and sigmoid curves. The model offers a means of studying multi-prey type functional responses from an optimal foraging point of view.