Environmental Effects on Food Hoarding in Deermice (Peromyscus)

Abstract

Five taxa of deermice, Peromyscus leucopus noveboracensis, P. l. castaneus, P. maniculatus bairdii, P. m. blandus , and P. e. eremicus , were studied in the laboratory for the amount of food hoarded under various combinations of test temperature (7°C or 27°C) and photoperiod (9:15 LD or 15:9 LD). The two northern subspecies, P. l. noveboracensis and P. m. bairdii , hoarded more food under cold temperature and short day photoperiod (simulating autumn or early winter) than they did under warm temperature and long day photoperiod (simulating summer). In contrast, neither P. l. castaneus nor P. m. blandus nor P. e. eremicus showed any significant difference in the amount of food hoarded under these same two test conditions. It was also found that test temperature had a greater influence than photoperiod on hoarding by P. l. noveboracensis , whereas just the opposite was true in P. m. bairdii v These findings indicate a selection for hoarding in deermice from northern latitudes (above 35° North Latitude) in response to seasonally low temperatures or a shortened photoperiod. Test temperature also had a significant effect on the hoarding of P. m. blandus , which hoarded more at 27°C than at 7°C. Increased hoarding by this subspecies under the warm test temperature may have resulted either because it remained more active under the warm temperature than the cold, or because warm temperatures in its environment (southwestern deserts) act as a cue to the need to store food during the summer months. The high level of hoarding observed for P. e. eremicus under all test conditions was interpreted as resulting from summer torpor in this desert species and its reliance on stored food while restricted to its burrows during extremes in ambient temperature. In all groups studied except perhaps P. m. bairdii , no evidence was found to support a model of food hoarding in deermice based on long-term nutritional needs or deficits (that is, losses in body weight) as has been proposed for laboratory rats.