Efeito da densidade de armadilhas e da precipitação na eficiência de gaiolas e pitfalls usados na amostragem de pequenos mamíferos na Amazônia Brasileira

Abstract

Effect of density of traps and precipitation in efficiency of live traps and pitfalls traps used in small mammals sampling in the Brazilian Amazon The sampling of non-flying small mammals uses live traps (Sherman and Tomahawk) and pitfall traps. These traps capture different species and their efficiency can be influenced by climatic factors, number and arrangement of traps, bait and duration of sampling. We compiled samples data of small mammals in 31 sites of upland forests in the Amazon to evaluate which of the three types of traps were more efficient in collecting rodents and marsupials. We also evaluated how precipitation in the month of collection and density of traps used in sampling, affected the efficiency of these traps. The pitfalls were more efficient than the live traps, capturing more individuals and species, especially the smaller. The precipitation and the trap density affected negatively the efficiency of capture of the three types of traps. The live traps were more affected by rainfall, while the pitfalls were most affected by the density of traps. In general, sampling with a high density of traps were less efficient. The availability of food, such as fruits and insects, increases in the rainy season, decreasing the attractiveness of baits. Heavy rains can also disarm the live traps, reducing its efficiency. For the pitfalls traps, the samplings that used high density of traps were the same that sampled a smaller area, reducing the likelihood of finding the trap by the animals. Smaller area also decreases the number of habitats and species to be sampled. For live traps, larger number of traps per area favors more sampling of individuals. We conclude that the type of trap, its distribution in the environment and precipitation influence the composition of small mammals sampled. These factors should be considered in the planning of small mammals sampling conducted in the Amazon.