Date of Award

12-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Forestry and Environmental Conservation

Committee Member

David S. Jachowski, Committee Chair

Committee Member

Susan C. Loeb

Committee Member

Brandon K. Peoples

Committee Member

Patrick G.R. Jodice

Abstract

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 Florida had higher arousal frequencies than those in South Carolina, the difference was not statistically different. Males aroused longer than females in the WNS negative sites but males and females in the WNS positive had similar arousals and potentially to minimize energetic costs in a diseased site. These findings suggest that P. subflavus are vulnerable to WNS among the sites because individuals’ skin temperatures were with the fungus’ optimal growth range (12⁰C – 16⁰C). To investigate winter activity within a hibernaculum, we acoustically monitored bat activity from October 2016 – March 2017 and October 2017 – March 2018 at a WNS positive site in South Carolina. While P. subflavus were active throughout the winter, activity was generally low. We used generalized linear mixed models to test the effects of environmental factors on activity within the hibernaculum and used Akaike Information Criterion to evaluate support for a top model. Presence of bat activity was positively correlated with ambient temperature and negatively correlated with hibernaculum temperatures and bats were more likely to be active later in the day. While we detected bat activity throughout the winter, levels of bat activity were lower in mid to late winter than early winter and levels of bat activity were positively correlated with hibernaculum temperatures. This suggests that P. subflavus were able to detect small changes within the hibernaculum and if activity increases with warmer temperatures, individuals could potentially expend more energy during an energetically constrained time.

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