State subsidies induce gray jays to accept greater danger: an ecologically rational response?

Abstract

Models of strictly rational choice assume that decision-makers evaluate options on relevant dimensions, assign fixed values to options, and then make consistent choices based on these values. If so, recent experience would have no impact on preference. But, recent events change an animal’s state, and preference may change accordingly. We explore how state affects willingness to accept greater danger to obtain larger food rewards. We tested how a supplement in state (hoard size) impacts this willingness in gray jays (Perisoreus canadensis). When subsidized, most of the subjects increased their willingness to trade danger for food. Why would they become less cautious when their hoard was increased? Superficially, it might seem prudent to play it safer in response to a subsidy. But imagining fitness as a sigmoid function of state (hoard size) provides a tentative explanation for our counterintuitive finding. Above a threshold hoard size, a subsidy should weaken the willingness to accept extra danger. Incremental increases in state in the deceleratory phase yield smaller fitness gains, so it would pay to increase emphasis on safety after receiving a subsidy. But below this threshold, incremental increases in state in the acceleratory phase yield bigger fitness gains, and so it would pay to decrease emphasis on safety after receiving a subsidy. Most of our subjects’ choice behavior was, thus, plausibly consistent with the possibility that effective hoard size is considerably smaller than the total number of items stored. We speculate that this response may reflect an ecologically rational compensation for the inevitable loss of hoards via theft and rot.