A Population of Little Brown Myotis (Myotis lucifugus) in Southern Ontario Exhibits Apparent Adaptation to White-nose Syndrome

Al Sandilands^1,* and Derek E. Morningstar²

¹Gray Owl Environmental Inc., 1356 Lockie Road, Branchton, ON N0B 1L0, Canada. ²Myotistar, 51 Silverthorne Drive, Cambridge, ON N3C 0B4, Canada. ^*Corresponding author.

Journal of North American Bat Research, Volume 2 (2024): 1–11

Abstract
Novel wildlife diseases are an increasing concern, as they can cause population declines in species unable to adapt, or result in crossover events, sickening humans. Myotis lucifugus (Little Brown Myotis), exhibited precipitous declines after exposure to Pseudogymnoascus destructans (Pd), the fungus that causes white-nose syndrome (WNS). Our objectives were to determine if Little Brown Myotis at a roost in southern Ontario had been exposed to WNS and, if so, what effects this had on the bats. All tested positive for Pd in spring, but had minimal wing-tissue damage (mean = 0.3 on the Reichard’s Wing Damage Index in May). Annual survival rate of adult females was approximately 0.83 ± 0.03, comparable to pre-WNS populations. The percentage of adult females that were lactating was 83.1%. All 3 subadult females that returned as yearlings lactated in their first year. Despite having been exposed to WNS, females had normal survival rates and reproductive success. This population appears to have developed resistance or tolerance to WNS. The prognosis for the Little Brown Myotis in southern Ontario may have shifted from imminent extinction to slow recovery.

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