Food deprivation-induced increases in hoarding by Siberian hamsters are not photoperiod-dependent

Abstract

Siberian hamsters increase food hoarding in response to chronic food restriction and food deprivation, conditions that lead to a loss of body mass and fat. Therefore, the first purpose of the present experiments was to test further the effects of food deprivation on food hoarding by varying the length and order of repeated fasts to address the following questions: 1. Does the magnitude of the food-hoarding response increase as food deprivation length increases? 2, Is the effect of food deprivation on food hoarding experience-dependent? Second, we were interested in testing the effects of short winter-like days (SDs) on food hoarding. We tested this by measuring food hoarding in long days (LDs) and SDs during baseline conditions and after food deprivation to address the following question: Does SD exposure increase baseline and food deprivation-induced hoarding due to the naturally occurring SD-induced decreases in body fat? During each experiment, we were interested in determining how hamsters utilize their food hoard (i.e., add to it and eat from it). Our results extended those of our previous studies in showing that: 1. Food-deprivation length and the initial food-hoard size were not related to one another; 2. The maintenance of food-hoard size was proportional to the length of the fast; 3. The effects of a bout of food deprivation on food hoarding were dependent upon the lengths of previous fasts; 4. Baseline food hoarding was not different between LD- and SD-exposed hamsters; 5. The maintenance of food-hoard size, but not the initial fast-induced increases in food-hoard size, were increased in SDs; 6. Hamsters ate approximately 25–33% of their daily food intake from the food hoard under all conditions, with the degree of food replacement increasing as fast length was increased; and 7. The typical SD-induced decrease in food intake was reflected in the food eaten from the food supply found outside the burrow, but food eaten from the hoard was increased. Collectively, the results of the present experiments suggest that the initiation of food hoarding may be associated with short-term fluctuations in energy metabolism associated with fasting, but that the more long-term decreases in body mass (fat) are involved in the maintenance of food-hoard size.