Beyond Selection: Optimal Ingestion Rate as a Function of Food Value

Abstract

A simple model based on microphagous feeders (animals which process their food items in bulk with little chance of selecting food items on an individual basis) was developed to predict how ingestion rate should vary with food quality if the net time rate of gain of some measure of food quality, say energy, is to be maximized. Three variants of the model were considered, in which absorption efficiency was constant, decreased linearly with increased ingestion rate or decreased exponentially. The optimal ingestion rate, which maximized the net rate of energy gain, depended on food quality and increased on higher quality foods. For certain parameter values, constantly maintaining the maximum ingestion rate resulted in maximal net energy gain. Experimental results from the literature on a variety of animals are not in consistent accord with these predictions. Uncontrolled and confounding variables, such as food composition or palatability, may obscure the effects of food quality on ingestion rate.