Granivorous forest mice select herb seeds on the basis of native origin, not seed size or microenvironment

Abstract Dietary choice of seed-consuming rodents potentially determines the survival and dispersal success of shade-tolerant forest herbs – a group at risk in post-agricultural landscapes of eastern North America. Optimal foraging theory predicts that large, energy-rich seeds will be most attractive and seed consumption will be greater in structurally complex habitats, which provide protection from predators. To assess the effects of seed size, familiarity, and habitat complexity, we set out seeds of six native herb species and six unfamiliar cultivated species at replicated feeding stations in a mixed-mesophytic deciduous forest in southeastern Ohio, USA. Seed removal was monitored daily. The neighborhood of each station was described in terms of microtopography, vegetation cover, woody debris, and leaf litter. Seed number declined at most stations over 1–3 weeks. Automatic wildlife cameras identified Peromyscus leucopus as the only biotic removal agent during the study. Loss of wooden-bead controls implied that seeds were also lost through abiotic processes, although at much lower rates. Cultivated species were removed earlier, faster, and more completely than native species regardless of seed size, indicating rodent preference for unfamiliar species. In native species, small seeds disappeared faster than large seeds consistent with abiotic seed loss. Local environment had little effect on seed removal. We conclude that P. leucopus is behaving as an opportunistic generalist granivore foraging without regard for predators. Low attractiveness of native species potentially allows survival of large-seeded herbs in the post-agricultural landscape. Energy content and microenvironment heterogeneity were not sufficient explanations for seed survival in a naturally complex forest community.