Going, going, gone: the impact of white-nose syndrome on the summer activity of the little brown bat (Myotis lucifugus)

Abstract

Since its discovery in the winter of 2005-2006, white-nose syndrome (WNS) has killed over one million little brown bats (Myotis lucifugus) in the American northeast. Although many studies have reported die-offs of bats at winter hibernacula, it is important to understand how bat mortality linked to WNS at winter hibernacula affects bat activity levels in their summer ranges. In the summer (May-August) of 2007, 2008 and 2009, we recorded echolocation calls to determine bat activity at sites along the Hudson River, NY (within approx. 100 km of where WNS was first reported). We documented a 78 per cent decline in the summer activity of M. lucifugus, coinciding with the arrival and spread of WNS. We suggest that mortality of M. lucifugus in winter hibernacula is reflected by reduced levels of activity in the summer and that WNS affects the entire bat population of an area, and not only individual hibernacula.

Figure 1.

Map of the northeastern United States indicating the location of the study area in relation to Howes Cave (filled triangle), where WNS was first reported in the winter of 2005–2006. Filled circles indicate sampling sites along the Hudson River.

Figure 2.

Summer bat activity during the spread of WNS. Little brown bats (M. lucifugus; filled bars) have been severely affected by WNS while hoary bats (L. cinereus; open bars) have not been affected. Myotis lucifugus activity decreased by 78% from 2008 to 2009, while L. cinereus experienced no precipitous declines. Sample sizes (number of 10 min files analysed) are indicated for each year.