Efeitos de diferentes matrizes no risco de predação e na movimentação de uma ave florestal / Effects of different matrices at risk of predation and movement of forest bird

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

03/09/2012

RESUMO

Forest fragmentation alters landscape structure and its relationship with organisms, and movement is one of the most affected behaviors. Individuals who are faced with an heterogeneous landscape, composed of habitat and non-habitat areas (i.e., matrix), need to cross the non-habitat matrix in the search for resources. The choice of motion is then made by an evaluation of the costs and benefits that each area provides to the animal. Among major costs while moving through the matrix is the risk of predation, which may vary with the structure of each matrix (e.g., vegetation cover) and the behavioral characteristics of each species (e.g. movement capacity). Aiming to analyze the effect of different matrices (pasture, corn and Eucalyptus) in relation to risk of predation for the species Pyriglena leucoptera (Tamnophillidae) we (1) determined if there were differences between matrices in the density of one of the main predators of the bird, birds of prey, and (2) inferred the perceived risk of predation by performing translocation experiments with radiotelemetry monitoring to describe and analyze movement patterns in the matrix. Our results suggested a predation risk gradient in the studied matrices (corn = pasture)>Eucalyptus. The time birds spent in the matrix until reaching a forest patch was also different among matrices (corn = Eucalyptus) >pasture. Movements were straighter over the pasture matrix and more tortuous in the corn matrix, while in the Eucalyptus matrix movment showed an intermediate pattern. The success of birds to reach a forest patch was higher in the Eucalyptus matrix, followed by the pasture and corn matrix. Corn is probably the riskiest matrix for Pyriglena leucoptera, having the highest density of birds of prey, with most tortuous movement patterns and longest time spent in the matrix (i.e., longer exposure to risk) which resulted in less successful arrival to forest patches. The pasture seems to be the matrix of intermediate risk, because despite a large density of birds of prey, birds spent less time exposed to the risk, making more straight paths, which resulted in a higher success of reaching the forest than in the corn matrix. Eucalyptus was the matrix of lowest risk, had the lowest density of birds of prey and the greatest success in reaching the habitat. In this case, however, tortuosity of movement and the long time spent in this matrix did not result in decrease success of reaching a forest patch, this suggests that birds may be using resources (i.e. foraging) while moving through this less-risky matrix. This project highlights the importance of studies that quantify the effects of matrix type on the movement of organisms through fragmented landscapes, which affects essential ecological processes linked to the persistence of species in these conditions. The proper management of matrices appears as a priority for conservation and restoration of biodiversity in these human-modified landscapes

ASSUNTO(S)

predação matrix ave bird matriz movement movimento predation

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