Constant vs. Variable Risk‐Aversion in Foraging Bananaquits

Abstract

Recent foraging theories predict that risk—averse foragers will trade off increases in mean reward against increases in reward variability. Different formulations of this trade—off have been proposed, with some models assuming constant risk—aversion and others assuming decreasing risk—aversion. A detailed analysis of indifference curves (when a forager shows equal preference for certain mean—variance combinations) can theoretically be used to discriminate between models. We follow the analysis of previous workers by equating decreasing risk—aversion with the predictions of the z—score model because those predictions suggest indifference curves that can be discriminated from the constant risk—aversion of the variance discounting model. Experiments conducted with captive Bananaquits (Coereba flaveola) foraging on nectar in an artificial floral patch indicate that they show a simple mean—variance trade—off. Bananaquit foraging behavior was consistent with the constant risk—aversion of the variance—discounting model, but was significantly different from decreasing risk—aversion represented by the z—score model.