Efeito de riachos, chuva e disponibilidade de presas na ocorrência de Bothrops atrox (Serpentes: Viperidae) em uma área de 25 km² na Amazônia Central

Abstract

Environmental variations condition the spatial distribution of most of the terrestrial organisms, probably including snakes by affecting their occurrence and detection. Previous studies suggest ecological relationships between snakes, water and weather conditions, but few of those consider detectability problems in their analysis. Such problems are relevant as snakes are cryptic animals and thus may be present at site yet not detected. The Lancehead, Bothrops atrox, is responsible for most of the snakebites in the Brazilian Amazon and is one of the most frequent species over the whole Amazonia: hence, the need to understand its occurrence and activity. Data were collected on the presence/absence of B. atrox in a 25 km2 area of terra-firme rainforest near Manaus, Amazonas. In this area, 47 sampling plots of 250 x 10 m were visited from four to five times within a one-year period. A maximum likelihood analysis was employed to estimate the effects of environmental variables (stream presence, stream order, prey [anuran] availability and rain occurrence) in this species occupancy and detection probability. It was observed that B. atrox usually occupies areas close to streams, being most easily detected close to first order streams. Rainfall occurrence had a strong influence in B. atrox detectability, while prey availability doesn t seem to be related to its detection.