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Abstracts

Naturschutz,
Entwicklungszusammenarbeit &
Wissenschaft
Netzwerk
2000.de

Fruit and Seed Predation and Dispersal by Small Mammals in Different Biotope Types in Central Amazonia (Manaus, Brazil)*

Göckler, Klaus F., Philipps-Universität Marburg, Germany. Kontact goeckler@newnet2000.de

Nowadays natural ecosystems get increasingly fragmented by human influence. Therefore it is important to know the ecological relationships within remaining fragments as well as between them. Habitat fragments and their organisms cannot be understood without knowing what happens around them.

The study has been carried out at the Embrapa-CPAA research site (Embrapa, Empresa Brasiliera de Pesquisa Agropecuária, is situtated 40 km north of Manaus) and has been supported by the German-Brazilian Cooperation Project SHIFT (Studies of Human Impact on Forests and Floodplains in the Tropics, Project ENV 23/2). The potential of predation and dispersal of mammals has been studied in three nearby situated habitat types (primary forest, secondary forest and mixed cultures). Predation experiments have been carried out using inajá-palmfruit (Attalea maripa) and brazil-nut (Bertholletia excelsa) in exclosures of different sizes. This way the activities of three classes of predators (invertebrates, small and respectively, large mammals) can be evaluated. Through tags it was possible to know the fate of most dispersed fruits and seeds.

Using these fruits/seeds the aim was evaluating the predation/dispersal potential of small mammals for each fruit type. These experiments have not been designed to make any statements according to the biology of the corresponding plants, but to compare the probability of a fruit/seed of these types getting established successfully in these habitats.

Results:

Small mammals: Abundances identified by life-trapping were very low and differed very little between primary and secondary forests; in the sites with mixed cultures they were totally absent. The trapped species correspond to the expectations (literature and personal communications). Introduced species (eg. Rattus sp.) have not been detected. In the mixed cultures no small mammals act as pests.

Biotope types: Predation and dispersal occur most intensive in primary forest, in secondary forest they are low, and in the mixed culture sites neglectable. The increased food supply of the mixed cultures has not been proven to be attractive to small mammals. Two of the more than fifteen cultivated plant species have been predated by monkeys from the adjacent primary and secondary forests. Agutis (Dasyproctidae) and monkeys often pass from one biotope type to another and they also disperse seeds doing this. For small mammals no passing between these biotope types has been proven.

Exclosures: The results show that invertebrates act in a very low proportion as predators or dispersers of the fruit/seeds used (with exception concerning the inajá seeds: esp. beetles act as "pre-dispersal seed predators"). Small mammals and large ones act differently: in the case of brazil-nuts small mammals have a higher proportion in predation and dispersal, while in the case of inajá-fruits both classes of mammals act as predators as well as as dispersers.

*  this is an abstract of a poster presented at a German-Brasilian Workshop on Neotropical Ecosystems held on 3.-8. Sept. 2000 at the University of Hamburg.