Frequent Arousal from Hibernation Linked to Severity of Infection and Mortality in Bats with White-Nose Syndrome

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.

White-Nose Syndrome-Affected Litttle Brown Myotis (Myotis Lucifugus) Increase Grooming and Other Active Behaviors During Arousals from Hibernation

White-nose syndrome (WNS) is an emerging infectious disease of hibernating bats linked to the death of an estimated 5.7 million or more bats in the northeastern United States and Canada. White-nose syndrome is caused by the cold-loving fungus Pseudogymnoascus destructans (Pd), which invades the skin of the muzzles, ears, and wings of hibernating bats. Previous work has shown that WNS-affected bats arouse to euthermic or near euthermic temperatures during hibernation significantly more frequently than normal and that these too-frequent arousals are tied to severity of infection and death date. We quantified the behavior of bats during these arousal bouts to understand better the causes and consequences of these arousals. We hypothesized that WNS-affected bats would display increased levels of activity (especially grooming) during their arousal bouts from hibernation compared to WNS-unaffected bats. Behavior of both affected and unaffected hibernating bats in captivity was monitored from December 2010 to March 2011 using temperature-sensitive dataloggers attached to the backs of bats and infrared motion-sensitive cameras. The WNS-affected bats exhibited significantly higher rates of grooming, relative to unaffected bats, at the expense of time that would otherwise be spent inactive. Increased self-grooming may be related to the presence of the fungus. Elevated activity levels in affected bats likely increase energetic stress, whereas the loss of rest (inactive periods when aroused from torpor) may jeopardize the ability of a bat to reestablish homeostasis in a number of physiologic systems.

Altered Behavior in Bats Affected by White-Nose Syndrome

WNS-affected bats did so over similar time frames as WNSunaffected bats. The behaviors of bats with WNS did not change as drastically as expected. Thereseems to be little to no effect on their ability to fly/forage until much later stages of the disease when they are likely near death. WNS-affected bats are grooming more which could be altering the way they use energy reserves during hibernation possibly leading tostarvation and eventually death. The decreased likelihood of arousals in response to external cues may be the result of spending more energy during previous and increasingly frequent arousals. While it is clear that WNS does result in changes in behavior whether these changes are directly in response to fungal skin infection or to some other component of the syndrome such as decreased energy availability or loss of homeostasis is unknown. bat behavior, white-nose syndrome, behavior, video surveillance, arousal patterns White-Nose Syndrome (WNS) is a disease of hibernating bats caused by the fungal pathogen Geomyces destructans. The fungus, which was first noted in 2006, invades bats wings and other exposed membranes, eventually resulting in death. Researchers have yet to understand many aspects of this disease, including basic etiology and epidemiology. There is also a lack of information on how fungal infection may change the behavior of healthy bats during hibernation or how changes in behavior may influence disease progression. Based upon the physiological changes that are known to occur in affected bats, and upon anecdotal observations of aberrant behavior in these bats, I hypothesized that WNS would significantly change the behavior of the little brown myotis (Myotis lucifugus). My research examined the behavior of hibernating bats during arousals from torpor. I compared WNS-affected and unaffected bats, in the field and incaptivity, using motion-sensitive infrared cameras. Flight maneuverability and echolocation were also tested between WNS-affected and unaffected bats during arousalsfrom hibernation to detect changes in the bats' ability to perform basic locomotion or potentially catch insect prey. Lastly, hibernating bats were artificially disturbed and theirarousal patterns were monitored to examine changes in the response to external stimuli between WNS-affected and unaffected bats.Bats with WNS groomed for longer periods of time after arousing from torpor, both in the field and in captivity. They also engaged in longer periods of any sort of activity during these arousals. There were no changes in acoustical signaling during flight tests and changes in flight maneuverability were only found in bats were seen staging" near the entrance of the mine which is itself a unique behavior exhibited by affected bats. At this point these bats were likely near death and could barely fly at all. In response toexternal stimuli bats with WNS were less likely to arouse than unaffected bats. However when they did arouse WNS-affected bats did so over similar time frames as WNSunaffected bats. The behaviors of bats with WNS did not change as drastically as expected. Thereseems to be little to no effect on their ability to fly/forage until much later stages of the disease when they are likely near death. WNS-affected bats are grooming more which could be altering the way they use energy reserves during hibernation possibly leading tostarvation and eventually death. The decreased likelihood of arousals in response to external cues may be the result of spending more energy during previous and increasingly frequent arousals. While it is clear that WNS does result in changes in behavior whetherthese changes are directly in response to fungal skin infection or to some other component of the syndrome such as decreased energy availability or loss of homeostasis is unknown."

Exploration Of Survival Traits In The White-Nose Syndrome-Affected Big Brown Bat (Eptesicus Fuscus)

The widespread mortality of hibernating bats is associated with the emerging infectious disease white-nose syndrome (WNS), and has provoked a strong interest in understanding which bats will survive, and why? The ability of infected bats to resist WNS may depend upon variation in the expression of different characteristics. In a captive colony of big brown bats, I sought to characterize the phenotypic variability, repeatability, and survivability for several key ¿survival¿ traits, including: torpor patterns, microclimate preferences, and wound healing capacity. Torpor patterns were profiled using temperature sensitive dataloggers throughout the hibernation season, while microclimate preferences were quantified by using temperature-graded boxes and thermal imaging. In order to assess wound healing capacity, small wing biopsies were obtained from each bat and healing progress was tracked for one month. Individuals exhibited a wide range of phenotypes that were significantly influenced by sex and body condition. Repeatability estimates suggest that there is not a strong genetic basis for the observed variation in torpor patterns or microclimate preferences. Certain phenotypes (e.g., BMI) were associated with an increased probability of overwinter survivorship, which suggests a basis for intra-species differences in WNS susceptibility. The results from this project provide novel insight into what we know about ¿who will survive,¿ and will influence the direction and implementation of future conservation and mitigation strategies.

The Effects of Hibernation on Immunological Functions in Female Big Brown Bats (Eptesicus fuscus)

The emerging disease White-Nose Syndrome in hibernating bat populations across the United States has increased the need to understand the physiological benefits and consequences of hibernation and the effects on immunological responsiveness. Hibernation has been well-documented in many mammalian species, yet few studies have examined hibernation immunology in bats, particularly with respect to normal immunological patterns. In order to characterize the levels of circulating leukocytes and plasma immunoglobulins in euthermic and hibernating female big brown bats (Eptesicus fuscus), blood smear differential leukocyte counts and total immunoglobulin assays were performed for each group using blood samples from the active and hibernation seasons. Hibernation patterns – torpor and arousals from torpor – were determined by placing temperature-sensitive dataloggers on the backs of bats assigned to the hibernating group during the hibernation season. Data indicate that the ratio of circulating neutrophils to lymphocytes is lower in bats assigned to the euthermic group during the hibernation season than in bats assigned to the hibernation group during the hibernation period, but that relative immunoglobulin levels do not differ during the hibernation season, regardless of whether bats were active or hibernating. Neither bats assigned to the hibernation group nor bats assigned to the euthermic group demonstrate a significant change in the ratio of circulating neutrophils and lymphocytes between their active and hibernating seasons. Bats assigned to the hibernation group were also observed to arouse from torpor somewhat synchronously. These results suggest that innate and adaptive cell levels are maintained, at best, in hibernating bats that are not immunologically challenged and that bats that remain euthermic during the hibernation season are able to continually regulate their levels of neutrophils and lymphocytes and therefore their innate and adaptive immune system responses.