905 words - 4 pages

Abstract

Organisms such as starlings and honeybees appear to forage based on the marginal value theorem. This experiment tested whether humans could forage in like manner. An equal number of students took long and short routes to the foraging patch and collected simulated food items in a way that simulated diminishing marginal returns. Data on travel time, foraging time, and number of food items collected were collected. The data differed significantly from the calculated optimal values. This may be a result of low number of trips between the foraging patch and the simulated dwelling.

Introduction

When animals forage, many factors become involved. They include the location of the food, its distance from the animals’ dwelling, and the quantity to be returned, among other things. Economic models, such as the marginal value theorem, can be used to predict the outcomes of many of these factors.

According to the marginal value theorem (Fig. 1), the food intake rate of the forager decreases with the time spent in the foraging patch (Charnov 1974).

Fig. 1. A graph of the marginal value theorem from Krebs (1993). The asymptotic curve represents food intake. The optimal number of food items to take is found by drawing a line from the travel time to the patch to the steepest point possible on the curve.

This model can be applied to a wide range of situations based on the factor to be maximized. Honeybees apparently maximize energetic efficiency, but other factors are possible (Schmid-Hempel et al. 1985). For example, the starling (Sturnus vulgaris) apparently maximizes feeding rate according to the marginal value theorem (Kacelnik 1984).

Our objective was to determine whether humans would optimize foraging behavior in the same way starlings appear to. We hypothesized that the median difference between the observed number of food items per trip and the optimal number of food items per trip would be 0.

Methods

A group of 14 students, aged 19-22 years, was divided into 7 groups of 2. Each member of every group was assigned either a long or short route to the simulated foraging patch, Room XXX. Students using the short route walked directly from the dwelling to the foraging patch, while students using the long route walked down a hallway, up a staircase, across the building, down a staircase, then into the foraging patch. Each run consisted of a group member leaving the dwelling, which contained a plastic cup representing offspring, entering the foraging patch, and returning. In the foraging patch, two trays of M & Ms were present. Students picked up one M & M from each tray during the first lap. On the second lap, students skipped one tray and picked up one M &...

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