Social class influences degree of variance sensitivity in wild Siberian jays

Variance sensitivity theory predicts that optimal foragers should take into account not only the mean but also the variance in rewards offered by alternative foraging options. Whereas a positive energy budget should favor variance aversion, a negative one should favor variance-prone choices. The risk of starvation is the most obvious fitness threshold that can select for variance-prone behavior, but additional thresholds may exist such as the energy required for reproduction. Previous studies of variance sensitivity have often been performed in captivity, and few have demonstrated the predicted state-dependent changes in individual variance preferences. We trained groups of wild Siberian jays (Perisoreus infaustus) to forage from one-shot feeders containing 3 color-coded options differing only in the variance of reward sizes. Not only did we find variance-sensitive behavior under natural conditions but also, for the first time, demonstrate the presence of significant differences in variance sensitivity within groups. Breeders exhibited a preference for high-variance rewards, whereas unrelated subordinates within the same groups preferred low-variance options. These results did not reflect risk of starvation (indexed by body mass) but might be explained by the additional energy needs of breeders compared with subordinates prior to the breeding season. Copyright 2010, Oxford University Press.