Abstract
In North America, the greatest and most sudden threat to hibernating bats is white‐nose syndrome (WNS), which has caused massive declines in populations since 2006. Other determinants of bat dynamics, such as the climate, and the effect of reduction in the number of individuals sharing foraging space and summer roosting habitat may have an effect on population dynamics. We analyzed transect acoustic bat surveys conducted with ultrasonic detectors in 16 regions in Quebec, Canada, between 2000 and 2015. We used piecewise regression to describe changes in activity over time for each species and a meta‐analytic approach to measure its association with the North Atlantic Oscillation (NAO). As expected, mouse‐eared bat (Myotis spp.) activity sharply declined after the onset of WNS, down by 79% after 3 years. In contrast, big brown/silver‐haired bat activity increased over the same period, possibly due to a release of competition. Hoary bats and red bats remained present, although their activity did not increase. Myotis activity was positively correlated with a one‐year lag to the NAO index, associated with cold conditions in winter, but warm autumns. Big brown/silver‐haired and hoary bats were also more active during NAO‐positive years but without a lag. We conclude that combinations of threats may create rapid shifts in community compositions and that a more balanced research agenda that integrates a wider range of threats would help better understand and manage those changes.
Highlights
In North America, one of the most sudden collapses of mammal populations on record is that of hibernating bat populations, caused by white-nose syndrome (WNS, Frick, Pollock, et al, 2010).After the initial discovery of a bat population contaminated by Pseudogymnoascus destructans (Pd; Ascomycota) in the State of New York (USA), over 5.5 million bats had died from whitenose syndrome (WNS) annually (Froschauer & Coleman, 2012), with a regional mean of mortality rates of 73% (Frick, Pollock, et al, 2010)
After the initial discovery of a bat population contaminated by Pseudogymnoascus destructans (Pd; Ascomycota) in the State of New York (USA), over 5.5 million bats had died from WNS annually (Froschauer & Coleman, 2012), with a regional mean of mortality rates of 73% (Frick, Pollock, et al, 2010)
We examine six predictions: (a) that Myotis species decline from the onset of WNS, consistent with estimates from the USA (Frick, Pollock, et al, 2010); (b) that such declines create a release from competition for foraging space leading to a relative increase in the activity of species unaffected by WNS; (c) that migratory bats decline with the creation of new wind energy facilities; (d) that stochastic fluctuations in bat activity are modulated by climatic variables; (e) that years with long and warm falls would benefit all bat species and result in an increased recorded activity the following summer; and (f) that mild winters are associated with high hibernating bat activity in the following summer for species at risk of hibernating in unstable conditions in caves
Summary
In North America, one of the most sudden collapses of mammal populations on record is that of hibernating bat populations, caused by white-nose syndrome (WNS, Frick, Pollock, et al, 2010). We examine six predictions: (a) that Myotis species decline from the onset of WNS, consistent with estimates from the USA (Frick, Pollock, et al, 2010); (b) that such declines create a release from competition for foraging space leading to a relative increase in the activity of species unaffected by WNS; (c) that migratory bats decline with the creation of new wind energy facilities; (d) that stochastic fluctuations in bat activity are modulated by climatic variables; (e) that years with long and warm falls would benefit all bat species and result in an increased recorded activity the following summer; and (f) that mild winters are associated with high hibernating bat activity in the following summer for species at risk of hibernating in unstable conditions in caves
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