Exploring the Connection between Arousal Patterns in Hibernating Bats and White Nose Syndrome

RCN Topic
Factors in Regional Decline of Species of Greatest Conservation Need

Funds from this RCN grant were used to demonstrate that bats affected with the infectious disease “White Nose Syndrome” (WNS) arouse from hibernation significantly more often than healthy bats, which leads to their starvation. This highly significant effect is independent of initial body condition and hibernacula microclimate, which are both known to influence hibernation patterns.

This study addressed the hypothesis that WNS bats are either arousing too frequently from torpor or exhibiting prolonged periods of euthermy (‘normal’ body temperatures) during the winter, either of which would cause them to starve to death by prematurely depleting stored body fat. Morphological data were collected from several hundred bats prior to the hibernation season, using temperature sensitive dataloggers  or radiofrequency (RF) transmitters. To control for the effects of hibernacula microclimate on torpor patterns, temperature sensitive dataloggers were deployed at each field site.

While this project was officially completed in 2010, because of the importance of the findings, and the continued rapid spread of WNS, we continued to monitor hibernation patterns in WNS affected bats using the supplies purchased with this grant supplemented by those purchased with other funds through the 2011 winter season. Approximately 150 dataloggers were available for the 2011 winter season, during which bats in several sites were surveyed for their third time. This long-term data is very valuable, and allows us to analyze the influence of WNS on a given hibernaculum overtime.  The final report and a journal article detailing the results of the study are available below.

White-nose syndrome (WNS), an emerging infectious disease that has killed over 5.5 million hibernating bats, is named for the causative agent, a white fungus (Geomyces destructans (Gd)) that invades the skin of torpid bats. During hibernation, arousals to warm (euthermic) body temperatures are normal but deplete fat stores. Temperature-sensitive dataloggers were attached to the backs of 504 free-ranging little brown bats (Myotis lucifugus) in hibernacula located throughout the northeastern USA. Dataloggers were retrieved at the end of the hibernation season and complete profiles of skin temperature data were available from 83 bats, which were categorized as: (1) unaffected, (2) WNS-affected but alive at time of datalogger removal, or (3) WNS-affected but found dead at time of datalogger removal. Histological confirmation of WNS severity (as indexed by degree of fungal infection) as well as confirmation of presence/absence of DNA from Gd by PCR was determined for 26 animals. We demonstrated that WNS-affected bats aroused to euthermic body temperatures more frequently than unaffected bats, likely contributing to subsequent mortality. Within the subset of WNS-affected bats that were found dead at the time of datalogger removal, the number of arousal bouts since datalogger attachment significantly predicted date of death. Additionally, the severity of cutaneous Gd infection correlated with the number of arousal episodes from torpor during hibernation. Thus, increased frequency of arousal from torpor likely contributes to WNS-associated mortality, but the question of how Gd infection induces increased arousals remains unanswered.

While this project is now officially completed (grant period ended 03/31/2010). However, because of the importance of these findings, and the continued rapid spread of WNS, we will continue to monitor hibernation patterns in WNS affected bats using the supplies purchased with this grant supplemented by those purchased with other funds. Approximately 150 dataloggers are available for studies next winter, during which bats in several sites will be surveyed for their third. This will provide for longitudinal analysis of the influence of WNS on a given hibernaculum over time (e.g., in an unaffected year, during the first year of infection, when mortality is high but some survivorship occurs, and in the second year of infection, in which nearly all remaining bats will perish).

Publication date
Publication date