The extent of land use for oil palm plantations has grown considerably in the tropics due to climate, appropriate soil conditions for cultivation and its profitability. However, oil palm plantations may endanger biodiversity through reduction and fragmentation of forest areas. Herein we analyzed the effects on anuran species richness, composition and total abundance in oil palm plantations and surrounding forests in eastern Amazon. We installed seven plots in oil palm plantations and seven plots in surrounding forests, which we surveyed for the presence of anurans through active visual and acoustic surveys during periods of high and low rainfall levels. Anuran assemblages found in forests and oil palm plantations differed in species richness and composition, with a loss of 54% of species in oil palm plantations. No difference was observed in total abundance of anurans between both environments. While conversion of forests to oil palm plantations may result in less negative impacts on anuran diversity than other types of monocultures, such loss is nevertheless high, making the maintenance of relatively greater forested areas around oil palm plantations necessary in order to conserve anuran diversity.
Both habitat fragmentation and predator abundance are known to affect habitat use. The current study analyzed the use of ponds by leaf-litter anurans in relation to distance to the forest edge and presence of aquatic predators in a forest fragment in Eastern Amazon. We selected three trails perpendicular to the forest edge, and in each trail we positioned nine plastic basins on the forest floor at different distances from the forest edge. From November 2011 to July 2012, each basin was surveyed monthly for presence of evidence of anuran breeding activity and aquatic predators. We recorded 112 instances of use of basins by four anuran species. While we did not observe any influence of distance to the forest edge on use of basins by Rhinella gr. margaritifera and Ameerega trivittata, there was differential use of basins by both species in relation to the presence of aquatic predators. In both cases, species used basins more often when aquatic predators were absent, suggesting that these species adopt strategies that reduce effects of predation and ensures the survival of some tadpoles, either by carrying tadpoles to ponds without predators or producing larger clutches.
Habitat structure is a factor that strongly affects the distribution of organisms. Habitats with high structural complexity provide a high number of microhabitats, allowing the coexistence of species with different behavioral, ecological and physiological requirements. We analyzed the effects of structural complexity of ponds on the number of males and foam nests of Physalaemus ephippifer, and the substrates to which individuals attach their foam nests. We sampled 41 ponds and recorded the number of individuals of P. ephippifer and environmental data (type of vegetation in, adjacent and around the pond; type of bottom substrate in the pond) to measure the degree of structural complexity of the ponds through an index ranging between 0 and 1. We found a positive influence of pond structural complexity on mean number of calling males, but not on number of foam nests. We found most foam nests attached to gramineans and herbaceous plants. Vegetation is an important component of habitats with high complexity, providing refuges for adults and tadpoles. The index was an efficient tool to measure habitat structural complexity, and may be used in further studies with other species.
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