Effect of a cold ambient temperature on the rat's food hoarding behavior.

In a first experiment, the amount of food hoarded in three hour sessions (HB) by eight food deprived rats, was measured at three ambient temperatures: 30, 17.5 and 5 degrees C. At the three temperatures, the mass of food pellets hoarded by the rats was linearly related to the rats' body weight (BW) with a negative slope. The slope of the regression lines was significantly higher at 5 and 17.5 degrees C than at 30 degrees C. In a second experiment, BW and HB of ten non-deprived rats were measured every day, first at 30, then at 10 degrees C, then at 30 degrees C again (70 days). In the cold environment, HB immediately increased without BW loss. This effect was immediately reversible by the adjunction of an insulating styrofoam mattress. HB of non deprived rats in the cold was therefore more a thermoregulatory behavior than an alimentary response. In a third experiment, ad lib fed or deprived rats could hoard either food pellets or styrofoam lumps at 30 degrees C or at 5 degrees C. In the cold environment, when non-deprived, the rats hoarded styrofoam rather than food. However, as soon as they were food deprived, they reversed their choice and hoarded food rather than styrofoam. It is concluded that food can be hoarded as a thermal insulator in a cold environment but HB is mainly an alimentary response increased by a cold stress.