Influence of food and water deprivation on the behavior of the white rat foraging in a hostile environment.

Rats were trained to feed 2 hr per day, the food offered being placed at 16 m from a warm refuge and the ambient temperature being - 15 degrees C. They were food deprived for 0, 12, 22, 46, 70 and 94 hr prior to the six feeding sessions. Speed of feeding and meal duration were not influenced by food deprivation. The amount eaten, the number of meals, the time spent at the feeder, the speed of running to the feeder and the number of foraging rats increased from 0 hr fast to 22 hr then plateaued for the 46, 70 and 96 hr fasts. The same experiment was carried out after water deprivation for 0, 12, 22, 46 and 70 hr. Rats could find, at -15 degrees C, water kept at 30-40 degrees C and at 16 m from their warm refuge. The speed of running to water and the rate of drinking were not influenced by water deprivation. The amount drunk, drinking-bout duration, the number of drinking-bouts, total drinking time and the number of rats drinking increased monotonically from 0 to 70 hr deprivation. Two main conclusions are drawn from these data: (1) in the rat, up to 70 hr deprivation, the motivation to feed seems to be stronger than the motivation to drink; (2) to satisfy hunger or thirst, the nervous system uses several different motor subsystems of behavior.