Tropical rodents change rapidly germinating seeds into long-term food supplies

Seed-hoarding vertebrates may survive yearly periods of food scarcity by storing seeds during the preceding fruiting season. It is poorly understood why rodents creating long-term reserves, especially those in the tropics, incorporate seeds from plant species that germinate rapidly and hence seem unsuitable for long-term storage. We carried out a series of experiments to understand why red acouchies (Myoprocta exilis) scatter-hoard Carapa procera (Meliaceae) seeds, which lack dormancy and germinate rapidly. Hypotheses tested were: (1) even germinated seeds are still significant long-term energy reserves for acouchies, (2) acouchies use the seeds only as short-term supplies, and (3) acouchies manipulate the seeds to slow down germination. The first two hypotheses were not supported; seed reserves were rapidly depleted during experimental planting, and acouchies did use seeds for long-term storage. We did find support for the third hypothesis. Acouchies intervened in germination by removing the protruding radicle and epicotyl after which they re-cached seeds. Pruning stopped further seedling development, yet the pruned seeds did not decay. The cotyledons apparently stayed alive and physiologically active as zombie seeds that only formed undifferentiated calli. Pruned seeds were suitable for long-term storage, with negligible loss of endosperm over time. Pruning was most effective after sprouting of the epicotyl, and germinating seeds were most susceptible to pruning during two weeks upon emergence. Acouchies actively managed their food supplies and must continuously survey for germinating seeds to timely intervene in seed reserve depletion, within the brief period of seedling emergence. We suggest that the trees use the rodents to achieve seed dispersal, and gain from imperfect intervention in germination by the rodents. Because scatter-hoarding rodents and large-seeded plant species with similar germination co-occur in tropical forests world-wide, it is plausible that the phenomenon of seed pruning to preserve seeds is more general than currently appreciated.