LAUSR

ABSTRACT Functional traits of plants and animals play a pivotal role in shaping mutualistic or predatory interactions within plant–animal systems, directly regulating the structure and function of forest ecosystems. Yet, the outcomes of multispecies interactions—particularly in seed–rodent systems—remain inadequately resolved, largely because traditional methods fail to track individual‐level interactions and seed fates with sufficient precision. To address this gap, we applied a novel double‐duplex passive integrated transponder (PIT) tagging technique to investigate the fates of seeds from four sympatric tree species (with distinct seed traits) when exploited by two sympatric rodent species (with contrasting body sizes) in a subtropical forest of Southwest China from 2018 to 2019. Our results revealed that rodent body size and seed size are key determinants of seed fates. The larger rat Niviventer confucianus scatter‐hoarded and consumed seeds of all four trees, with a significant preference for large‐sized seeds of Quercus variabilis and Lithocarpus harlandii. In contrast, the smaller mouse Apodemus draco did not hoard the large‐sized seeds of L. harlandii and showed a significant preference for small‐sized seeds of Camellia oleifera. Additionally, N. confucianus exhibited a higher interspecific pilfering rate on seeds of C. oleifera and L. harlandii than A. draco . Our study highlights the significant role of size traits in shaping the mutualistic or predatory interactions in seed–rodent systems and demonstrates the utility of individual‐based tracking in disentangling complex species interactions.