Motivational factors involved in food-carrying behavior of rats: a review

The present paper reviews studies on the choice between food-carrying and food-eating behaviors in foraging rats. First, influences of external (e. g., food size and distance to food) and internal factors (e. g., hunger levels and differences between the sexes) on the animals' choice are separately discussed. For example, rats tend to eat the food at the site where they find it if its size is small, but to carry it to their nest if the size is large. Second, several functional aspects of food-carrying behavior are discussed by taking all of the factors into consideration. It is suggested that the choice between food-carrying and food-eating behaviors is mainly based on a trade-off or a motivational conflict between hunger and risk avoidance; that is, carrying food has an advantage of avoiding a predatory risk by shortening the time staying outside the nest, whereas eating at the food site immediately reduces hunger. It is also suggested that individual differences and physiological mechanisms involved in this choice should be studied in the future.