Granivores play a major role in forested ecosystems as both seed predators and seed dispersers. In temperate forests, rodents have the potential to greatly impact forest composition based on their foraging preferences. Forest rodent communities are dominated by deer mice, Peromyscus which are active year-round and may show differences in their foraging preferences based on seasonal changes in climate, such as shorter photoperiod and lower temperatures. This study explores the immediate shifts in foraging behavior of woodland deer mice (Peromyscus maniculatus gracilis) caused by sudden onset of fall weather. The immediate effects of a shift in seasonality include a significantly delayed onset of nocturnal activity, but do not include a shift in offset of nocturnal activity. We simulated a seasonal change in photoperiod and temperature for wild-caught mice in the laboratory, and measured foraging preferences for two common maple species, red maple (Acer rubrum) and sugar maple (Acer sacchraum). Previous work has shown that P. m. gracilis has a strong preference for A. rubrum in the summer. We expected a shift in preference to A. saccharum under autumn conditions.
Foraging preferences were altered after experimental seasonal shifts. Under the stress of a shift in seasonality, P. m. gracilis showed an increased preference for A. saccharum seeds. Further analysis of foraging behavior, through an index which calculates the probability that uneaten seeds were handled, suggests that mice are more likely to handle A. saccharum seeds under autumn conditions. The shift in foraging behavior caused by the primacy effects of seasonal shifts supports the hypothesis that these foraging behaviors have an underlying seasonal rhythm.