Tropical rainforests often appear relatively homogeneous on satellite images, but responses to landscape characteristics may be found on finer scales if habitat characteristics are considered as continuous variables. In this study, we used 30 uniformly distributed plots and 16 plots beside streams to evaluate the effects of distance from stream, litter depth, altitude, slope, and tree density on abundance of Amazonian Lancehead Pitviper (Bothrops atrox). We estimated densities and probabilities of detection of snakes in riparian and upland plots in Reserva Ducke, Manaus, Amazonas, Brazil. Apparent density of individuals of B. atrox was about 6.4 times higher near streams, but the number of individuals in the landscape more than 10 m away from streams was about 3.9 times higher than the number of individuals within 10 m of streams. Movement data from two adult B. atrox evaluated by radio telemetry indicate that individuals can disperse out of plots and away from streams over a period of several months. Detectability of B. atrox varied little among riparian and upland plots, so differences in detectability are unlikely to be responsible for large differences in encounter rates of snakes between riparian and non-riparian areas. There were small differences in body size of individuals near streams and individuals far from streams. The distribution of B. atrox is not uniform within the forest. However, as with most other tropical-forest organisms studied to date, this species occurs across wide environmental gradients and shows only subtle habitat specificity.
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Vol. 2013 • No. 4