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© 1998 International Society for Behavioral Ecology
research-article |
Testing predictions of foraging theory for a sit-and-wait forager, Anolis gingivinus
aDepartment of Biological Sciences, Stanford University CA 94305, USA bDepartment of Geophysics, Stanford University CA 94305, USA
ABSTRACT
Research in foraging theory has been dominated by studies of active foragers choosing among patches and among prey within a patch. Studies of central-place foraging have mainly focused on loading decisions of an animal provisioning a central place. The problem faced by a sit-and-wait forager that encounters prey at a distance has received little attention. In this study we tested foraging theory predictions for such foragers, Anolis gingivinus females in the West Indies island of Anguilla. We presented lizards with antlion larvae at various distances. Experiment 1 showed that an individual's probability of pursuing prey decreases with the prey's distance and is best described by a sigmoidal function (which may be as steep as a step function). This function's inflection point defines a cutoff distance. Experiment 3 tested how cutoff distance changes as a function of prey size. Cutoff distances were greater for larger prey, as predicted for an energy-maximizing forager. Experiments 2 and 4 tested how cutoff distance changes as a function of prey abundance. As predicted, cutoff distance were greater at a site where prey abundance was lower. Furthermore, cutoff distances decreased immediately following prey augmentation and returned to previous values within one day of ending augmentation. Thus, moles' foraging behavior is a dynamic process, consistent with the qualitative predictions of foraging theory. We attribute the success of this study in supporting fundamental foraging theory predictions to the lizards exhibiting natural behavior under field conditions and to particular advantages of studying sit-and-wait foragers.
Key words: Anguilla, Anolis gingivinus, cutoff distance, encounter at a distance, foraging theory, lizards, partial preferences, prey abundance, prey size, sit-and-wait foragers, threshold, zero-one rule.