Scatterhoarding of Manchurian walnut Juglans mandshurica by small mammals: response to seed familiarity and seed size

Dispersal patterns can be affected by seed familiarity and seed traits, including size, mass, and nutritional value, but these factors have not been intensively studied in the context of seed dispersal processes. Our aim was to study how small rodents respond to seed size and seed familiarity in their pattern of Manchurian walnut (Juglans mandshurica) seeds in two different habitats in temperate forests of northeast China. Our results demonstrated that Apodemus penisulae acts as the most important disperser for Manchurian walnut seeds. Inexperienced small rodents did not reject seeds of the Manchurian walnut and show similar seed removal rates as compared with experienced rodents. Both experienced and naïve rodents actively participated in seed scatterhoarding of Manchurian walnut seeds. Consecutive survey showed that seeds with large size/mass were removed faster than those with small size/mass, indicating a preference for large seeds. However, small seeds scatter-hoarded by small rodents were transported farther than large ones, failing to support the traditional optimization models for various tree species. Small seeds of Manchurian walnut in caches were less likely to be recovered than large ones and showed greater cache survival rates, indicating that small seeds would be more advantageous for regeneration than large seeds in small rodent-dominated forests.