Abstract
BackgroundIn temperate regions many small mammals including bats hibernate during winter. During hibernation these small mammals occasionally wake up (arouse) to restore electrolyte and water balance. However, field data on water stress and concentration of bodily fluids during hibernation is scarce. Urinary creatinine concentration has long been used to calibrate urinary hormone concentration due to its close correlation with urine concentration. Therefore, by investigating urinary creatinine concentration, we can estimate bodily fluid concentration. In this study, we investigated changes in urinary creatinine from greater horseshoe bats (Rhinolophus ferrumequinum) hibernating in abandoned mineshafts in two regions in South Korea.ResultsWe collected 74 urine samples from hibernating greater horseshoe bats from 2018 to 2019. We found that urinary creatinine concentration was higher in February and March and then declined in April. There were also indications of a sex difference in the pattern of change in creatinine concentration over the three months. Bats in the warmer and less humid mineshaft had higher urinary creatinine concentrations than bats in the colder and more humid mineshaft.ConclusionsThese results indicate that hibernating bats face water stress as urinary concentration increases during winter and that water stress may vary depending on the microenvironment. Sex differences in behaviour during hibernation may influence arousal frequency and result in sex differences in changes in urinary creatinine concentration as hibernation progresses. Although further behavioural and endocrinal investigations are needed, our study suggests that urinary creatinine concentration can be used as a proxy to estimate the hydration status of bats and the effect of sex and environmental factors on arousal patterns during hibernation.
Highlights
In temperate regions many small mammals including bats hibernate during winter
Since TA and relative humidity (RH) data were only available for January to April 18 2019, we could not compared TA and RH for 2018
TA was higher in H1 than Mineshaft 1 in Anseong (A1), and RH was higher in A1 than H1
Summary
In temperate regions many small mammals including bats hibernate during winter. Some bat species may form large clusters during hibernation to reduce evaporative water loss, and may arouse to drink water inside or outside the hibernaculum [6,7,8]. Bats can provide a unique perspectives and information to the field of hibernation research [15, 16]. The same bat species in different regions may differ in activity patterns and physiological parameters during hibernation depending upon the microclimate of the hibernaculum and the climate outside. Females may adjust torpor and arousal duration to save energy for foetal development after hibernation [22] These differences in reproductive strategies between sexes may result in individual variations in physiological parameters of hibernating bats
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