The tri-colored bat (Perimyotis subflavus) is a hibernating species with a statewide distribution in North Carolina. This species, once common, has recently experienced population declines exceeding 70% in western North Carolina where White-nose Syndrome (WNS) and the caves that harbor it are widespread. WNS is disease caused by the fungus, Pseudogymnoascus destructans (Pd), which first showed up in a cave in New York in 2006 but has origins in Europe. Pd grows in cold, dark, damp conditions like those found in caves and mines where it attacks the bare skin of hibernating bats. Infected bats awake repeatedly to clean off the fungus and often deplete fat reserves before Spring arrives and their insect prey are active on the landscape.
WNS appeared in the NC Mountains in 2011 and has caused population declines across the region in the ensuing years. As WNS continued its spread across the Mountains, N.C. Wildlife Resources Commission (NCWRC) biologists began searching for bat hibernacula (caves and underground mines) in the Piedmont Region, which had not been a traditional focus for NCWRC bat monitoring. Though few caves exist east of the Southern Appalachian Mountains in NC, recent efforts by NCWRC biologists uncovered a link between the nation’s first Gold Rush and hibernating tri-colored bats. The first documented discovery of gold in the US occurred in Cabarrus County in 1799 and kicked off 50 years of gold mining in the state, drawing miners from across the globe. The NC Gold Rush was eclipsed by the more familiar California Gold Rush in 1848, but gold mining continued to a lesser degree in NC for another century. Though not as productive as its California counterpart, the NC Gold Rush left hundreds of underground portals throughout the Piedmont Region, providing critical hibernation habitat for the tri-colored bat in a region where caves are scarce.
Nine of these mines were surveyed by NCWRC in winter 2019, including two on Three Rivers Land Trust property. NCWRC staff counted 86 tri-colored bats, 30 of which hibernated in a single site. This count is slightly greater than the highest counts in Mountain hibernacula, some of which formerly held thousands of tri-coloreds before the arrival of WNS. Fungal swabs were collected from each site, and mines in Montgomery, Rowan, and Gaston County tested positive for Pd. This brings the total number of Piedmont Counties with Pd presence to five. While this result was disappointing, no signs of fungal growth were seen on bats and Piedmont sites that tested positive for the pathogen in the past continue to show stable counts. This could be an indication that WNS is unable to grab a foothold in the Piedmont Region, perhaps due to the warmer, shorter winters that provide small amounts of insect activity for bats to re-build fat reserves. The explanation for continued health among these tri-colored bats remains unclear, but one thing is for sure, NCWRC biologists are finding inactive gold mines now hold a different kind of treasure.
How You Can Help
The NCWRC is seeking new survey sites and landowners with underground mines or caves on their property can contact Katherine Etchison at katherine.caldwell@ncwildlife.org for more information about conducting a bat survey.
Consider installing a bat house, which provides roosting habitat for bats during warm months. See Bat Conservation International for tips on buying, building, and installing bat houses.
Be an ambassador for bats! Bats are often underappreciated and sometimes even feared, so spread the word about the importance of bats. North Carolina is home to 17 species of bats that play a critical role in our ecosystems by keeping insect populations in check, including mosquitoes! Additionally, bats save the US agricultural industry over $3.7 billion dollars annually in pesticide use (Boyles et al. 2011). For more information on bats, see Bats of North Carolina and Coexist with Bats.
References
Boyles, J. G., P. M. Cryan, G. F. McCracken, and T. H. Kunz. 2011. Economic Importance of Bats in Agriculture. Science 332: 41-42.