Scatter-hoarding by Central American agoutis (Dasyprocta punctata) differentially affects large seed survival, germination, and seedling growth

Background/Question/Methods

Central American agoutis (Dasyprocta punctata, Rodentia) bury a portion of the seeds they find in single, shallow subsurface caches – a process known as scatter-hoarding. Although the potential positive effects of scatter-hoarding on seeds have been well-studied, the negative effects of scatter-hoarding on seeds and resultant seedlings are unknown. If hoarded seeds escape predation and become seedlings, they are still susceptible to herbivory by terrestrial mammals. In this study, I tested the hypothesis that scatter-hoarding by agoutis enhances seed survival, germination, and growth by protecting seeds from seed predators. I also determined how large terrestrial mammals affected recently-germinated seedlings. Using seeds of four large-seeded plants (Astrocaryum alatum, Iriartea deltoidea, Socratea exorrhiza, and Dipteryx panamensis), I simulated agouti hoards and exposed seeds to invertebrate or vertebrate seed predators for 36 d. I recorded germination success and growth of seedlings produced from seeds infested and non-infested by Coccotrypes beetles. Using mammal exclosures, I recorded the survival of seedlings exposed to or protected from large terrestrial mammals for 140 d.

Results/Conclusions

Hoarded seeds escaped predation by both invertebrates and vertebrates while exposed seeds suffered high beetle infestation or almost complete removal by mammals. After 36 d, 0 - 11% of hoarded seeds were infested by insects (per depot, on average) compared to 40 - 92% of non-hoarded seeds. Terrestrial mammals removed 0 - 10% of hoarded seeds and 30 - 99% of exposed seeds within 36 d.  Hoarding negatively affected seeds of D. panamensis by preventing germination: only 7% of hoarded seeds germinated after 50 d compared to 89% of non-hoarded seeds. Non-infested palm seeds had higher germination success (P < 0.001) and produced larger seedlings (P < 0.001) than palm seeds infested by Coccotrypes beetles. Seedlings of A. alatum and I. deltoidea suffered high mortality by peccaries and agoutis with 33% and 0% of unprotected seedlings alive after 140 d, respectively. Hoarding by agoutis protected most seeds from predators and enhanced germination success (except for seeds of D. panamensis) and seedling growth, although mammals killed many seedlings of two plant species. Scatter-hoarding by agoutis is beneficial to most seeds and may positively affect plant propagation and resultant seedling survival in lowland Neotropical forests.