Relationship between exogenous factors and rodent abundance in a remnant of Araucaria Rainforest, Rio Grande do Sul, Brasil

Abstract

In regions affected by seasonal variation in environmental conditions and resources availability, rodent species abundance and composition tend to fluctuate, following these environmental changes. In this study, we evaluated the relationship between exogenous factors and the variation in rodent abundance in an Araucaria Rainforest remnant in northern Rio Grande do Sul. We used pitfall traps with guide fences and wire traps to collect species and to estimate their abundance, between June 2009 and January 2010. Posteriorly, we used Non-metric Multidimensional Scaling and Pearson correlation analysis in order to investigate the relationship between exogenous factors and changes in rodent abundance across the sampled seasons. At the end of our study, we captured 54 individuals belonging to 10 rodent species. Oligoryzomys nigripes (Olfers 1818), registered in all seasons and Akodon montensis (Thomas 1913), which was not recorded only in the spring, were the most abundant species in the study area. We found that temperature was correlated to the first axis of variation of rodent abundance. Moreover, the increase of Sooretamys angouya (Thomas 1913), Thaptomys nigrita (Lichtenstein 1829) and Akodon azarae (Fischer 1829) abundances were negatively correlated with temperature, while the opposite pattern was observed for Akodon paranaensis (Christoff et al. 2000), Oligoryzomys flavescens (Waterhouse 1837) and Mus musculus (Linnaeus 1758). Finally, our study contributes to the definition of factors related to rodent population dynamics and to increase the knowledge about the rodent composition in Araucaria Rainforest remnants in Rio Grande do Sul.