PARENT SESSION
Oral Session #101: Plant-Animal Interactions.
Presiding: S. Faeth
Friday, August 9. 9:00 AM to 12:00 PM. Coconino Meeting Room, TCC.
Effects of small rodent seed predators on forest recruitment in Corcovado National Park, Costa Rica.
DEMATTIA, ELIZABETH*,1, CURRAN, LISA2, RATHCKE, BEVERLY1, 1 UNIVERSITY OF MICHIGAN, ANN ARBOR, MI2 YALE UNIVERSITY, NEW HAVEN, CT
ABSTRACT- Studies of tropical forest seed predation have concentrated on large mammals. We examined seed predation by small rodents in Corcovado National Park, Costa Rica to test whether: 1) small rodents were significant seed predators; 2) their effect differs in primary and secondary forests; and 3) their effect was mediated by the exclusion of large mammals. The 54,000 ha park has an intact mammal community, including both small rodent and large mammalian seed predators. To measure small rodent seed predation, we established three treatments in two forest types (8 replicates in primary forest and 8 replicates in secondary forest): i) fenced exclosures that excluded large mammals, ii) fenced exclosures that excluded both large and small mammals, and iii) open controls. In each treatment we added tethered seeds from seven species of common canopy trees, and measured seed removal for 28 days. Our results show that three species had significant seed predation rates (40-97% of the seeds were destroyed): Virola sp., Brosimum costaricanum, and Clarissa tuna. Seed predation rates in these species did not differ significantly between forest types nor between the two exclosure treatments. Therefore, the high predation rates were caused primarily by small rodents. The strong preferences and high predation rates indicate that small rodents (Oryzomys talamancae, Melanomys caliginosus, Heteromys desmarestianus, and Proechimys semispinosa) can be significant seed predators and could influence the establishment and composition of Neotropical forest's seedlings.
KEY WORDS: Rodents, Costa Rica, Seed-predation