Behavior, body mass, and sex: how intraspecific variation influences seed dispersal by a scatterhoarding rodent

1. Intraspecific variation plays a pivotal role in shaping ecological dynamics. As the dispersal of seeds of most woody plants is mediated by animals, individual variation within the animal dispersers holds considerable implications for plant population and ecology. 2. We explored how individual traits (such as sex, body mass, and exploration levels) of yellow-necked mice (Apodemus flavicollis) impact the dispersal of common oak (Quercus robur) acorns. Over three years, we collected data on seed fate and the specific mice responsible for their dispersal. 3. The relationship between individual traits and seed dispersal was not static, but influenced by yearly environmental conditions. Heavier individuals tended to carry seeds farther, yet contrary to our expectations, sex had no effect on the distance of seed dispersal. Moreover, the exploration rate showed an inconsistent association with seed consumption and dispersal distance, while it positively impacted the distance of dispersal from the nearest tree. 4. Synthesis. Our findings suggest a more nuanced role of individual traits in seed dispersal than often assumed, with noticeable annual variation significantly influencing these impacts. Consequently, it appears there is no single, universally beneficial individual type to ensure maximal benefits to plants. Rather, the traits conferring advantages in seed dispersal are dynamic, subject to change over time in response to environmental context.