Abstract
<jats:p>Seed dispersal outcomes are highly context-dependent, emerging from the interaction of multiple biotic and abiotic factors. However, key determinants of the seed shadow, including successive dispersal movements, remain poorly understood in complex dispersal systems involving seed-hoarding animal communities. Here, we quantify such determinants in a complex multi-species oak–forager system in Northern California, USA. We evaluated how forager identity, oak species (Quercus agrifolia vs. Q. lobata), acorn weight, post-dispersal acorn fate (non-eaten, partially eaten, fully eaten), deposition microsite, and interannual variation in acorn production (mast vs. non-mast years) shape dispersal outcomes across multiple stages. Dispersal patterns were strongly context-dependent, with forager identity being the dominant predictor of initial dispersal and re-dispersal movements. At initial dispersal, deer mice (Peromyscus californicus) and tree squirrels (Sciurus niger) dispersed acorns over the shortest distances, followed by woodrats (Neotoma fuscipes) and ground squirrels (Otospermophilus beecheyi), whereas jays (Aphelocoma californica) dispersed acorns the longest distances, although these differences were significant only during the non-mast year. Acorn traits also modulated dispersal distance, with Q. agrifolia acorns and those of intermediate weight being dispersed farther than Q. lobata (larger in size and lower in tannin content) acorns. Notably, early dispersal context largely determined final seed shadow outcome, whereas redispersal generally increased seed predation while providing only marginal additional dispersal distances. By adopting a community-level, multi-stage approach, we show that spatial outcomes are shaped by a complex interplay of biological, behavioral, and environmental drivers. Rather than emerging from the cumulative effects of successive dispersal events, final seed shadows appear to be largely determined by the earliest stages of dispersal, highlighting the disproportionate influence of initial dispersers and their early decisions on recruitment opportunities.</jats:p>