**4. Impacts of WNS**

The impact of WNS on the total number of *M. lucifugus* in North America has been drastic, despite the partial recovery of some populations in New York State. A recent analysis of winter hibernaculum counts for 5 bat species performed in 27 U.S. states and 2 Canadian over a 23-year period was performed by Cheng et al. [48]. Their analysis revealed that the total number of *M. lucifugus*, *M. septentrionalis*, and *P. subflavus* hibernating at these sites decreased by over 90% with the first 7 years after the arrival of *Pd*, and the number of *M. sodalis* decreased by 84%. The decline in the number of *M. septentrionalis* was so great that the U.S. Fish and Wildlife Service designated it a threatened species in 2016. A total of 47 different bat species are found in North America, and about half of them are known to hibernate during the winter [49]. Although the susceptibility of 8 of these hibernating bat species to WNS is well understood, the ability of *Pd* infections to cause WNS in other species of hibernating North American bats is virtually unknown. The National Wildlife Health Center of the U.S. Geological Survey thus began a WNS surveillance program in 2013 to address the potential effects of *Pd* as it spreads across the USA. Each year the wildlife agencies of 22 U.S. states submit thousands skin surface swabs collected from free-ranging bats during either the fall or hibernation to the National


#### **Table 1.**

*North American species of hibernating bats and their known levels of susceptibility to cutaneous infection with Pseudogymnoascus destructans.*

Wildlife Health Center which are examined for *Pd* DNA. Skin biopsies collected from bats showing signs of fungal infection are also submitted for histological analyses [A. Ballman, personal communication]. The result of these surveys are summarized in the WNS webpage maintained by the U.S. Fish & Wildlife Service [50]. The degree to which each species of hibernating North America bat is susceptible to cutaneous *Pd* infections and WNS has been compiled in **Table 1** using both the results of both the surveys conducted by National Wildlife Health Center as well as the published studies cited previously. The susceptibility of 7 of the 21 bat species listed in **Table 1** to *Pd* infections during hibernation is currently unknown due to a lack of data for these species. The DNA of *Pd* has been found on the skin surface of *Myotis ciliolabrum*, *Corynorhinus townsendii*, and *Lasionycteris noctivagans* indicating that *Pd* now occurs with the range of these species, but it is not known if *Pd* can invade their skin and produce lesions. Skin lesions caused by *Pd* infections have been documented in hibernating *Myotis yumanensis*, *M. volans*, and *Myotis velifer*, but it is not known if the density of *Pd* lesions that appear during this period is sufficient to cause WNS. The degree of *Pd* infection that occurs in *Myotis austroriparius*, *M. grisescens*, *Myotis leibii*, and *E. fuscus* is not sufficient to cause WNS in these species.
