Rats eating and hoarding as a function of body weight and cost of foraging.

Abstract

Rats were trained to forage 2 h daily in a zigzag alley at -15 degrees C. On experimental days food was placed in large amounts at a 1-, 4-, or 16-m distance from a warm shelter. The mass of food ingested and hoarded in the shelter by the rats was then recorded. The rats' body weights were depressed progressively by spacing the sessions with access to food, and then the animals were allowed to recover their initial body weight. The results showed that 2-h food intake was constant and did not vary as a function of body weight loss or the distance to reach the food (cost). On the other hand, the mass of food hoarded was a linear increasing function of body weight loss below the hypothetical set point for body weight and a decreasing linear function of the distance to the food. The linear regression of the mass of food hoarded on body weight with a negative slope (b) adequately depicted the rat's hoarding behavior: mass hoarded = a + b (body wt). The slope of this function decreased with increasing cost of food procurement. It is concluded that 1) the main response of the rat to starvation is food hoarding rather than ingestion and 2) the estimation of the body weight set point from hoarding is not affected by the costs of food procurement.