Vulnerability of Tri-Colored Bats (Perimyotis subflavus) to White-Nose Syndrome in the Southeastern United States

Tri-colored bats (Perimyotis subflavus) have experienced significant population declines in the southeastern United States due to white-nose syndrome (WNS). The lack of information on the torpor patterns and winter activity in conjunction with the rapid decline from the disease has led to an increased effort in researching the hibernation physiology and wintering activity of P. subflavus and their response to WNS in southern hibernacula. To address this growing concern, we used temperature sensitive radio transmitters to examine torpor patterns in three geographically distinct states and acoustic detectors to monitor bat activity within a WNS-positive hibernaculum. Our specific objectives were 1) compare torpor patterns (torpor bout length, number of torpor bouts, arousal length, arousal frequency, and average skin temperature) between a WNS-positive and two WNS-negative sites, 2) examine the environmental factors that affect torpor patterns in the southeastern United States, and 3) investigate the environmental factors that affect P. subflavus winter activity within a hibernaculum. To compare torpor patterns between WNS-positive and WNS-negative sites, we affixed temperature sensitive radio transmitters on P. subflavus in South Carolina (WNS positive), Mississippi (WNS negative), and Florida (WNS negative) during winters 2016-17 and 2017-18. We used linear mixed effects models to compare torpor between the WNS-positive and negative sites. We also tested the effects of environmental factors (hibernaculum temperature, ambient temperature, humidity), sex, and site on torpor parameters. P. subflavus average torpor skin temperatures ranged from 12.5⁰C to 15.8⁰C across sites and were within the optimal growth range of the fungus that causes WNS. Torpor bout length, number of torpor bouts, and average torpor skin temperature did not differ between sites. However, males had longer torpor bout lengths than females. Bats in South Carolina had higher arousal frequencies than bats in Mississippi, and even though bats in Fl