Raw microclimate data from caves and mines in New Brunswick, Canada

We document white-nose syndrome (WNS), a lethal disease of bats caused by
the fungus Pseudogymnoascus destructans (Pd), and hibernacula microclimate
in New Brunswick, Canada. Our study area represents a more northern region
than is common for hibernacula microclimate investigations, providing
insight as to how WNS may impact bats at higher latitudes. Hibernacula
microclimate is important in hibernaculum selection by bats and may also
be an important factor influencing WNS-associated bat mortality rates. To
determine the impact of the March 2011 arrival of Pd in New Brunswick and
the role of hibernacula microclimate on hibernating bat mortality, we
surveyed bat numbers at hibernacula twice a year from 2009 – 2015. We also
collected data from iButton temperature loggers deployed at all sites and
gathered temperature and humidity data from HOBO loggers at three sites.
Bat species found in New Brunswick hibernacula include Myotis lucifugus
(Little Brown Bat) and M. septentrionalis (Northern Long-eared Bat), with
small numbers of Perimyotis subflavus (Tricolored Bat). All known
hibernacula in the province were Pd-positive with WNS-positive bats by
winter 2013. A 99% decrease in the over-wintering bat population in New
Brunswick was observed between 2011 and 2015. We did not observe P.
subflavus during surveys 2013 – 2015 and the species appears to be
extirpated from these sites. Bats did not appear to choose hibernacula
based on winter temperatures, but dark zone (zone where no light
penetrates) winter temperatures did not differ among our study sites,
likely due to the geographically small sampling area. Dark zone
temperatures did not vary among years, unlike hibernacula entrance
temperatures, but both locations were affected by the presence of flowing
water. Winter dark zone temperatures were warmer and less variable than
entrance or above ground temperatures. We observed visible Pd growth on
hibernating bats in New Brunswick during early winter surveys (November),
even though hibernacula temperatures were colder (~ 4 – 5°C) than optimum
for in vitro Pd growth (12.5 – 15.8°C). This suggests that cold
hibernacula temperatures encountered near the apparent northern range
limit for Pd do not sufficiently slow fungal growth to prevent the onset
of WNS and associated bat mortality over the winter. As WNS continues to
spread west across continental North America, the severity of WNS-related
mortality may therefore be greater at northern latitudes where bat
hibernation periods are longer, despite apparent suboptimal temperatures
for Pd growth.