Habitat use and seasonal activity of insectivorous bats (Mammalia: Chiroptera) in the grasslands of southern Brazil

ABSTRACT

In temperate zones, insectivorous bats use some types of habitat more frequently than others, and are more active in the warmest periods of the year. We assessed the spatial and seasonal activity patterns of bats in open areas of the southernmost region of Brazil. We tested the hypothesis that bat activity differs among habitat types, among seasons, and is influenced by weather variables. We monitored four 1,500-m transects monthly, from April 2009 to March 2010. Transects corresponded to the five habitat types that predominate in the region. In each sampling session, we detected and counted bat passes with an ultrasound detector (Pettersson D230) and measured climatic variables at the transects. We recorded 1,183 bat passes, and observed the highest activity at the edge of a eucalyptus stand (0.64 bat passes/min) and along an irrigation channel (0.54 bat passes/min). The second highest activity values (0.31 and 0.20 bat passes/min, respectively) were obtained at the edge of a riparian forest and at the margin of a wetland. The grasslands were used significantly less (0.05 bat passes/min). Bat activity was significantly lower in the winter (0.21 bat passes/min) and showed similar values in the autumn (0.33 bat passes/min), spring (0.26 bat passes/min), and summer (0.29 bat passes/min). Bat activity was correlated with temperature, but it was not correlated with wind speed and relative humidity of the air. Our data suggest that, in the study area, insectivorous bats are active throughout the year, and use mostly forest and watercourses areas. These habitat types should be considered prioritary for the conservation of bats in the southernmost region of Brazil.