Mean-variance sets for dietary choice models: simplicity in a complex world

Summary This paper presents a series of simulations designed to determine optimal diet breadth under shortfall avoidance models. Profitability and encounter rate functions were varied, and means and variances of energy intake rate were generated using a simple simulation procedure. The resulting mean-variance sets assumed three distinct shapes: u-shaped, arched, and looped. These simulations show that certain mean-variance sets allow the forager to employ simple behavioural rules to determine the optimal diet breadth. This situation occurs when low ranking diet items have small handling times, and these conditions may be quite common. In other cases, mean-variance sets may be too complicated to allow for easy behavioural rules designed to minimize starvation probability. The ability to characterize foraging problems into a limited series of mean-variance set types benefits workers examining the evolution and maintenance of foraging strategies, since these sets have clear implications for the ability of animals to develop simple behavioural rules. Unfortunately data are lacking on the profitability and encounter rate distributions animals face in nature.