Seed dispersal by brown bears promotes trophic facilitation in a human‐dominated landscape

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Abstract Seed dispersal is a key ecological process with wide‐ranging implications for plant population dynamics, forest regeneration, and biodiversity maintenance. The role of carnivores and omnivores as endozoochorous dispersers is increasingly acknowledged. However, empirical studies on how other species use seeds after defecation remain scarce, particularly in Eurasia. We examined post‐dispersal seed removal from scats of brown bears ( Ursus arctos ) in the Cantabrian Mountains (NW Spain), focusing on seeds of wild cherries ( Prunus avium ) during peak fruiting season. Using trail cameras (608 trap‐nights) and environmental variables, we assessed how cherry tree density, rodent occurrence, vegetation cover, and carnivore activity shaped seed removal by rodents and scat visitation by birds. Rodents removed seeds from 65% of the monitored bear scats, and birds visited 93% of the scats. Seed removal from bear scats by rodents decreased in areas of high cherry density, suggesting that alternative food availability reduces reliance on gut‐passed seeds. Rodent occurrence was higher near scats where seed removal occurred, but it did not predict removal rates. Vegetation cover did not influence rodent seed removal but reduced bird visitation, likely due to decreased visibility and increased perceived predation risk. Rodents delayed seed removal after other carnivores were present around the scats, revealing risk‐sensitive foraging behavior, but overall seed removal was not suppressed by carnivore presence. Birds visited scats mainly during daylight and were likely attracted by invertebrates associated with the feces rather than by seeds themselves. Our findings reveal a two‐stage dispersal system: primary endozoochory by brown bears followed by potential synzoochory via scatter‐hoarding rodents. These interactions may enhance plant recruitment by relocating seeds to low‐competition microsites, aligning with theoretical expectations of dispersal benefits. Our results represent the first empirical evidence of this two‐stage process in Eurasia and demonstrate that brown bears act both as seed dispersers and as trophic facilitators, provisioning resources for rodents. Recognizing the multifunctional ecological roles of large omnivores and rodents is crucial in the current context of seed dispersers' decline. This study underscores the need to consider highly interactive species within broader ecosystem functioning and conservation frameworks.

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