Navigating novel resources: A field test of the effects of small mammal personality on dispersal of Quercus seeds

Climate change is shifting the habitable ranges of hundreds of species, and a greater understanding of the mechanisms driving migration velocity may make the difference between extinction and persistence for at-risk species. However, predicting migration velocity is particularly complicated for sessile organisms that rely on animals for the dispersal of their propagules. Extrinsic factors (e.g., seed availability, forest structure) and intrinsic factors of propagules and dispersers (e.g., seed mass, disperser species) interact to influence the seed dispersal process at multiple levels, complicating the conditions under which mutualism can occur. Small mammals are important seed predators and dispersers, and thus, their collective actions may modulate the migration velocity of seed-bearing plants. Recent studies have revealed the importance of disperser intraspecific variation, but the role of behavioral variation—animal personality—is infrequently studied and remains poorly understood. Personality may be critical to consider in the context of novel seeds as inexperienced individuals may default to specific behavioral tendencies and foraging strategies when deciding if and how to utilize resources. In a large-scale field experiment in central Maine (USA), we examined seed selection behavior in two species of small mammals (Peromyscus maniculatus and Myodes gapperi) for eight species of Quercus acorns—two of which are native to Maine and six of which are novel to our populations but expected to migrate northward. We found no discernible effects of seed novelty at any stage of the seed dispersal process, but we found evidence of personality-driven patterns in caching behavior. Docility positively predicted removal probability in voles and distance to burrow caches in mice. Lastly, individual antagonism–mutualism scores for voles were influenced by personality, where shy individuals were more antagonistic to acorns and bold individuals were more mutualistic. Put together, our results indicate that behavioral diversity may be important to consider for the maintenance of ecological function and provide a basis from where conservationists can work toward clarifying plant fitness in their novel ranges, species-specific extinction probabilities, and future trends in forest regeneration.