Behavioral strategies in the cold: Effects of feeding and nesting costs

animals can meet energetic challenges by acquiring or conserving energy. In the present experiment, we pitted these strengths against each other by ho using rats in a cold environment and requiring them to bar press for food p ellets and for access to a heated nest. Our question was how rats would exp loit these resources to meet the added energetic demand of the cold when fo od was abundant or scarce. Results showed that rats' allocation of time and effort between competing activities was a function of demand. Feeding and nestling were partially substitutable in the cold: rats traded food for war mth and vice versa, economizing on both time and energy by adjusting their feeding and nestling patterns. Depending upon food abundance and the cost o d nesting, rats acquired calories from food, conserved calories by nestling , and borrowed calories from the defense of body weight. (C) 1999 Elsevier Science Inc.