Capture and Reproductive Trends in Summer Bat Communities in West Virginia: Assessing the Impact of White-Nose Syndrome

Abstract

Although it has been widely documented that populations of cave-roosting bats rapidly decline following the arrival of white-nose syndrome (WNS), longer term reproductive effects are less well-known and essentially unexplored at the community scale. In West Virginia, WNS was first detected in the eastern portion of the state in 2009 and winter mortality was documented in 2009 and 2010. However, quantitative impacts on summer bat communities remained unknown. We compared “historical” (pre-WNS) capture records and reproductive rates from 11,734 bats captured during summer (15 May to 15 August) of 1997–2008 and 1,304 captures during 2010. We predicted that capture rates (number of individuals captured/net-night) would decrease in 2010. We also expected the energetic strain of WNS would cause delayed or reduced reproduction, as denoted by a greater proportion of pregnant or lactating females later in the summer and a lower relative proportion of juvenile captures in the mid–late summer. We found a dramatic decline in capture rates of little brown Myotis lucifugus, northern long-eared M. septentrionalis, small-footed M. leibii, Indiana M. sodalis, tri-colored Perimyotis subflavus, and hoary Lasiurus cinereus bats after detection of WNS in 2009. For these six species, 2010 capture rates were 10–37% of pre-WNS rates. Conversely, capture rates of big brown bats Eptesicus fuscus increased by 17% in 2010, whereas capture rates of eastern red bats Lasiurus borealis did not change. Together, big brown and eastern red bats were 58% of all 2010 captures but only 11% of pre-WNS captures. Reproductive data from 12,314 bats showed shifts in pregnancy and lactation dates, and an overall narrowing in the windows of time of each reproductive event, for northern-long-eared and little brown bats. Additionally, the proportion of juvenile captures declined in 2010 for these species. In contrast, lactation and pregnancy rates of big brown and eastern red bats, and the proportion of juveniles, were similar to historical patterns. Our results further elucidate the significance of short-term effects and provide a basis to examine long-term consequences of WNS.

Changes in Capture Rates in a Community of Bats in New Hampshire during the Progression of White-Nose Syndrome

“…There is less agreement among studies of Eastern Small-footed Bats. Our results were somewhat similar to those of Francl et al (2012), who detected declines in Eastern Small-footed Bats (84%) that were comparable to those of Little Brown Bats (80%) and Northern Long-eared Bats (77%). In contrast, estimates from overwintering bats suggest lower rates of decline in Eastern Small-footed Bats (12%) than in other species affected by WNS (Turner et al 2011).…”

“…We did not assess abundance of a fifth species, Tricolored Bats, because they were rare in New Hampshire prior to WNS, but estimates from hibernacula suggest that the species has experienced exceptionally high rates of WNS-induced mortality (Langwig et al 2012, Turner et al 2011. Thus, the community of bats at Surry Mountain Lake likely had declined from 7 species before WNS to effectively 4 species (Big Brown Bat, Eastern Small-footed Bat, Eastern Red Bat, and Hoary Bat) by 2010-2011. Declines in capture rates that we observed largely agree with those presented in previous studies, suggesting populations of Little Brown Bats and Northern Longeared Bats experienced drastic declines in the Northeast following arrival of WNS, which were more severe than those experienced by Big Brown Bats (Brooks 2011, Dzal et al 2011, Francl et al 2012, Langwig et al 2012, Turner et al 2011, Wilder et al 2011. There is less agreement among studies of Eastern Small-footed Bats.…”

“…Brooks (2011) and Dzal et al (2011) detected substantial declines in acoustic activity of bats in the genus Myotis, most likely M. lucifugus LeConte (Little Brown Bats) and Northern Long-eared Bats, in New England. Additionally, Francl et al (2012) compared relative abundance of bats captured in mist nets in West Virginia from 12 years before WNS, to data gathered the year after WNS was first observed in that state. They are the only authors to examine responses by Eastern Small-footed Bats, and their results suggest Eastern Small-footed Bat populations and those of 5 other species were reduced following the arrival of WNS (Francl et al 2012).…”

“…Additionally, Francl et al (2012) compared relative abundance of bats captured in mist nets in West Virginia from 12 years before WNS, to data gathered the year after WNS was first observed in that state. They are the only authors to examine responses by Eastern Small-footed Bats, and their results suggest Eastern Small-footed Bat populations and those of 5 other species were reduced following the arrival of WNS (Francl et al 2012).…”

Prelude to a panzootic: Gene flow and immunogenetic variation in northern little brown myotis vulnerable to bat white-nose syndrome

“…If WNS causes a significant selective sweep at MHC in M. lucifugus across the continent, bats that survive WNS may experience a trade-off in susceptibility to other pathogens; a carryover effect of the disease that extends its influence past the stage of acute infection and recovery. Examples of other potential carryover effects from WNS include delayed parturition (Francl et al 2012) and increased chronic stress following recovery (Davy et al 2017). …”