Seeds of Doubt: Feeding Preferences of Peromyscus leucopus and Peromyscus maniculatus gracilis on Acer Seeds

Background/Question/Methods

Seed predation is a prevalent plant-animal interaction that has wide-reaching effects on many ecosystems. In forests, small mammals are voracious seed predators, and many studies have documented their effects on forest structure and species composition. Whereas many have studied the effects of sciurid seed predators, fewer have focused on cricetid rodents, despite the evidence that mice are highly effective seed predators. Making direct observations of these species is difficult, given their small size and nocturnal activity. Those that do consider cricetid rodents, especially Peromyscus, generalize across species due to the difficulty in making positive identifications in the field, and also because of the assumption that Peromyscus species are ecologically similar. This study explores foraging choices made by wild-caught seed predators (Peromyscus leucopus and P. maniculatus gracilis) presented with seeds of two common tree species (Acer saccharum and A. rubrum) in a controlled laboratory setting. I hypothesized that both species would prefer A. saccharum seeds, as they are larger and ostensibly contain more energy. 

Results/Conclusions

I found that although both species consumed the same amount of seed, there was a species-specific difference in preference. P. leucopus showed no consistent preference for either Acer species, whereas P. m. gracilis clearly preferred A. rubrum over A. saccharum. P. leucopus, being a habitat generalist, may demonstrate higher plasticity in response to different food types. P. m. gracilis may prefer A. rubrum because of differences in nutrition, handling costs, or germination schedules. This species-specific difference in preference indicates that researchers should exercise caution when assuming that Peromyscus species are ecologically similar.