Sampling and information acquisition by western scrub-jays, Aphelocoma californica

Abstract

Animals often make choices based on cues that provide uncertain information about the value of alternative options. To examine how this uncertainty affects sampling behaviour, western scrub-jays were studied in the field during selection of single food items to scatter-hoard. Nine habituated birds were videotaped at feeders during repeated presentations of pairs of unshelled peanuts that varied in size. Jays initially scanned the peanuts before picking one up and in 38% of trials handled both, often switching repeatedly between them before making a choice. The jays preferred heavier nuts, which contained a larger food reward, but made errors particularly when mass differences were small. In addition, when choosing which nut to pick up first the birds discriminated mass relatively less accurately when the peanuts were larger. When mass differences were small the birds were more likely to handle both nuts before choosing. Handling both nuts raised the probability of selecting the heavier one by 20%, but did not increase the rate of food acquisition above that obtainable by scanning because it also increased time spent choosing. These results confirm recent suggestions that animals facing difficult discriminations may increase the accuracy of choice by sampling additional cues.