Coping with food-limited conditions: Feeding behavior, temperature preference, and nocturnal hypothermia in pigeons

Abstract

The adaptive responses to increasing food scarcity were investigated in a closed economy behavioral procedure. Food-limited conditions were simulated by an increasing fixed ratio (FR) schedule, i.e., an increasing number of keypecks was required to give the pigeons access to a food dispenser. The birds could influence the ambient temperature (Ta) by breaking light beams. The body weight (b.wt.), the deep body temperature (Tb), the selected Ta, the pecks to the food key, and the number of food accesses were continuously recorded. As the FR increased, the pigeons first showed an improvement of the feeding behavior. When this behavioral adaptation failed to maintain a sufficient food intake, the b.wt. of the pigeons gradually decreased and nocturnal hypothermia occurred. Interrelated to nocturnal hypothermia, the birds changed their Ta preference. Only when their b.wt. had reached approximately 70% of its initial value, the birds increased their feeding activity. At all ranges of food scarcity, the pigeons reached a steady state. The work provides evidence about the way adaptive mechanisms interact within the response complex to food-limited conditions.