Risk-sensitivity: ambient temperature affects foraging choice

Abstract

Short-term physiological requirements strongly constrain some foragers. During the limited time available for foraging, they must consume sufficient food to meet all energetic expenditures for 24 h. Models for risk-sensitive, decision-making predict that such a forager should be risk-averse toward reward variance when the animal expects to meet its requirement, and should be risk-prone toward reward variance when expecting an energetic deficit. Some previous demonstrations of this shift from risk-averse to risk-prone behaviour relied on differences in both pre-experimental deprivation and inter-trial delays within an experiment to vary the subjects' energy budgets, and these differences have allowed an alternate interpretation of observed preferences. Therefore, earlier work on risk-sensitive foraging in small birds was complemented by manipulating ambient temperature to induce positive and negative expected energy budgets. For a given mean reward, the inter-trial delay was the same, constant length at both temperatures. When subjects experienced a positive energy budget (warm temperature), risk-aversion exceeded preference for risk strikingly; the opposite occurred when the subjects could anticipate a negative energy budget (cold temperature). Variation in inter-trial delays could not have influenced the change in preference reported here.