Héctor Ruiz-Villar, Area of Zoology, Department of Biodiversity and Environmental Management, Faculty of Biological and Environmental Sciences, University of León

Seed dispersal is a key ecological process shaping plant dynamics and biodiversity. While carnivores and omnivores are increasingly recognized as endozoochorous seed dispersers, little is known about the use of seeds by other species after defecation, particularly in Eurasia. We studied post-dispersal seed removal from brown bear (Ursus arctos) scats in the Cantabrian Mountains (NW Spain), focusing on wild cherry (Prunus avium) during peak fruiting. Using trail cameras (608 trap-nights) and environmental variables, we assessed how cherry tree density, rodent abundance, vegetation cover and carnivore activity influenced seed removal by rodents and visitation rates by birds. Rodents removed seeds from 65% of scats, while birds visited 93% of the scats. Seed removal by rodents decreased in areas with high cherry density, suggesting reduced reliance on gut-passed seeds when alternative resources were abundant. Rodent abundance was higher near scats with seed removal, although it did not predict removal rates. Vegetation cover reduced bird visitation, likely due to decreased visibility and increased perceived predation risk. Rodents delayed seed removal following carnivore presence, indicating risk-sensitive foraging, though overall removal was not suppressed. Birds were likely attracted to invertebrates associated with scats rather than seeds. Our results reveal a two-stage dispersal system, combining primary endozoochory by brown bears with potential secondary dispersal by scatter-hoarding rodents. This process may enhance plant recruitment by relocating seeds to low-competition microsites. We provide the first empirical evidence of this two-stage dispersal system in Eurasia and demonstrate that brown bears act not only as seed dispersers but also as trophic facilitators, provisioning resources for rodents. These findings highlight the multifunctional roles of large omnivores and rodents in ecosystem functioning and conservation.