Influence of underground mining with explosives on a hibernating bat population

Bats arouse from hibernation both naturally and in response to disturbances. Frequent bat arousals can decrease survival due to increased energetic costs. An active sand mine in west-central Wisconsin hosted over 52,000 hibernating bats of 4 species in inactive tunnels, and regularly blasted with explosives to remove sand. We collected environmental and acoustic data at this mine during two hibernation seasons (November 1 through February 28 in 2013-2014 and 2014-2015) to examine the effect of blasting on echolocation calls (bat activity), a measure of bat arousal from hibernation. We used total bat activity recorded 7 h before and 7 h after blast time as the response variable, assigned it to a binary category and used that as a fixed effect. We used explosive charge per delay (kg), number of blasts per day, number of consecutive blast days, barometric pressure, temperature, and hibernation season as fixed effects. We used generalized linear mixed models with a negative binomial distribution and Bayesian information criterion (BIC) for model selection. The BIC-optimal model did not include any of the variables associated with blasting, but included activity timing, temperature, barometric pressure, and season as fixed effects, of which all were significant. Blasting did not influence bat activity significantly in this mine.