Subtropical mouse-tailed bats use geothermally heated caves for winter hibernation

Abstract

We report that two species of mouse-tailed bats (Rhinopoma microphyllum and R. cystops) hibernate for five months during winter in geothermally heated caves with stable high temperature (208C). While hibernating, these bats do not feed or drink, even on warm nights when other bat species are active. We used thermo-sensitive transmitters to measure the bats' skin temperature in the natural hibernacula and open flow respirometry to measure torpid metabolic rate at different ambient temperatures (T a , 16-358C) and evaporative water loss (EWL) in the laboratory. Bats average skin temperature at the natural hibernacula was 21.7 + 0.88C, and no arousals were recorded. Both species reached the lowest metabolic rates around natural hibernacula temperatures (208C, average of 0.14 + 0.01 and 0.16 + 0.04 ml O 2 g 21 h 21 for R. microphyllum and R. cystops, respectively) and aroused from torpor when T a fell below 168C. During torpor the bats performed long apnoeas (14 + 1.6 and 16 + 1.5 min, respectively) and had a very low EWL. We hypothesize that the particular diet of these bats is an adaptation to hibernation at high temperatures and that caves featuring high temperature and humidity during winter enable these species to survive this season on the northern edge of their world distribution.

Variable Climates Lead to Varying Phenotypes: “Weird” Mammalian Torpor and Lessons From Non-Holarctic Species

“…Interestingly, mouse-tailed bats (Rhinopoma) are even considered incapable of entering torpor during cold periods (Kulzer, 1965). Levin et al (2015) found that two species of mouse-tailed bats (Rhinopoma cystops, Rhinopoma microphyllum) hibernated in a geothermally heated cave in winter with a stable ambient temperature of 19-23.8 • C although colder caves were available. Both species showed the lowest torpor metabolic rate at ∼20 • C and aroused at ambient temperature below 16 • C (Levin et al, 2015).…”

“…Levin et al (2015) found that two species of mouse-tailed bats (Rhinopoma cystops, Rhinopoma microphyllum) hibernated in a geothermally heated cave in winter with a stable ambient temperature of 19-23.8 • C although colder caves were available. Both species showed the lowest torpor metabolic rate at ∼20 • C and aroused at ambient temperature below 16 • C (Levin et al, 2015). Thus, the availability of warm caves has allowed them to expand their subtropical distribution range from semi-arid and warm regions in Asia and Africa into southern Israel, the northern edge of their distribution (Levin et al, 2008(Levin et al, , 2015.…”

The H2S–Nrf2–Antioxidant Proteins Axis Protects Renal Tubular Epithelial Cells of the Native Hibernator Syrian Hamster from Reoxygenation-Induced Cell Death

“…Intriguingly, during hibernation, organs resist injury from the above cycles of I-R [4,5]. The discovery that in certain species, hibernation takes place with the preservation of high body temperature is significant, since, in human I-R injury, body temperature remains stable [6]. Finally, the identification of certain primate hibernators makes the study of this phenomenon extremely interesting, as these species are evolutionarily close to humans [7,8].…”

Energy handling in renal tubular epithelial cells of the hamster, a native hibernator, under warm anoxia or reoxygenation

“…However, studies have demonstrated that these mammals resist warm I-R injury more than other phylogenetically related species that are unable to hibernate (8,9). Evidence has revealed hibernation in high ambient and body temperatures, a phenomenon observed even in primates (10,11). Therefore, besides resistance to cold I-R injury, resistance to warm I-R injury also occurs in certain hibernators, some of which are phylogenetically close to humans.…”