Disentangling Multitrophic Interactions: How Vegetation Cover, Wild Boar, Deer, and Predators Shape Rodents Activity and Acorn Dispersal

Complex multitrophic interactions influence key ecosystem functions. In Mediterranean oak forests, both ungulates and rodents consume acorns, with rodents acting as effective seed dispersers. Rodents are in turn subjected to predation and disturbance by carnivores and ungulates. Most studies assess only pairwise interactions between rodents and their predators or competitors. In this study, we combined camera trapping and piecewise structural equation modeling to evaluate how vegetation structure, carnivores, deer, and wild boars influence rodent activity and their role as seed dispersers. Rodent activity increased with shrub density, as they find protection under vegetation cover. However, at a finer scale, rodent activity was unrelated to carnivore records. Camera traps allowed separating the effects of different ungulate species. While wild boars had a direct negative effect on rodent activity and hence an indirect negative one on acorn dispersal, deer had no effect on rodents. Unlike wild boars, deer do not trample and root in the soil, destroying burrows and even predating rodents. Most acorns were dispersed under shrubs by rodents, and the effect of rodent activity on dispersal distances was entirely mediated by vegetation cover. By explicitly separating the effects of different large-sized mammals, our study identifies wild boars as the main disruptor of mice activity and rodent-mediated seed dispersal. These results emphasize the need to investigate ecological processes, considering the combined influence of all interacting species. Our approach reveals hidden pathways that single-factor studies often miss and provides valuable insights for managing forest regeneration and biodiversity.