Disparate roost sites drive intraspecific physiological variation in a Malagasy bat

Reher, Stephanie; Rabarison, Harison; Montero, B. Karina; Turner, James M.; Dausmann, Kathrin H.

doi:10.1007/s00442-021-05088-2

Cited by 8 publications

(12 citation statements)

References 111 publications

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“…Since we did not trap any bats in the forest during the dry season, we only ran these measurements in the wet season (N = 10). The data from these experimental set-up were then compared to the physiological responses of bats resting in their native roost type, which are summarized and analyzed in an ecological context, i.e., focusing on habitat and roosting conditions but not acute microclimate changes, in Reher et al (2022).…”

Section: Study Set-upmentioning

confidence: 99%

“…Of all data sets, including those collected under natural conditions that sometimes lasted several days (Reher et al, 2022), only the first day of a measurement (from earliest 21:00 to ∼ 30 min before sunset) was analyzed. Moreover, because the forest environment is somewhat milder and both, warm (cloudy, rainy) and very hot days, can occur during the rainy season, we only included data from forest bats measured on hot days (N = 12 bats), which better reflected the southern regular weather.…”

Section: Data Processing and Analysesmentioning

confidence: 99%

“…For TMR, we included the lowest 70% of data per hour and per individual. Macronycteris commersoni is known to enter torpor bouts of varying lengths, including micro-torpor bouts lasting 12-20 min on average (Reher and Dausmann, 2021;Reher et al, 2022). However, the bats rarely entered micro-bouts in the manipulated conditions, and we therefore only included torpor bouts lasting ≥ 1 h for downstream analysis.…”

Section: Data Processing and Analysesmentioning

confidence: 99%

“…Furthermore, RH a was excluded from the analyses in the fluctuating environmental set-ups because it is not independent from T a . We also did not include body conditions and pooled the data of females and males, as both were not important predictors when modeling RMR or TMR during longer torpor bouts in M. commersoni (Reher et al, 2022). Data exploration and model validation were done following Zuur et al (2009), Zuur et al (2010) and Zuur and Ieno (2016).…”

Section: Cave Bats Exposed To Experimental Forest Conditions (Wet Sea...mentioning

confidence: 99%

“…This species is one of the most widely distributed bat species in Madagascar (Goodman, 2011). In addition to exposed foliage, it also roosts in larger colonies in caves, which offer buffered, more stable microclimates (Reher et al, 2018), and torpor patterns, i.e., frequency, duration and timing, vary depending on respective roost condition (Reher et al, 2022). Both cave and forest populations are vulnerable to several threats: cave populations in southwestern Madagascar have already declined substantially due to ongoing unsustainable hunting and individuals may no longer be able to use the caves when disturbance persists (Goodman, 2006;Andriafidison et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

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Limited Physiological Compensation in Response to an Acute Microclimate Change in a Malagasy Bat

et al. 2022

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Rapid environmental changes are challenging for endothermic species because they have direct and immediate impacts on their physiology by affecting microclimate and fundamental resource availability. Physiological flexibility can compensate for certain ecological perturbations, but our basic understanding of how species function in a given habitat and the extent of their adaptive scope is limited. Here we studied the effect of acute, experimental microclimate change on the thermal physiology of two populations of the widespread Malagasy bat, Macronycteris commersoni. Populations of this species are found roosting under contrasting conditions, i.e., in a constant hot and humid cave or below foliage unprotected from fluctuations in ambient conditions. We exposed free-ranging individuals of each population to the respective opposite condition and thus to novel microclimate within an ecologically realistic scope while measuring metabolic rate and skin temperature. Cave bats in forest setting had a limited capacity to maintain euthermia to the point that two individuals became hypothermic when ambient temperature dropped below their commonly experienced cave temperature. Forest bats on the other hand, had difficulties to dissipate heat in the humid cave set-up. The response to heat, however, was surprisingly uniform and all bats entered torpor combined with hyperthermia at temperatures exceeding their thermoneutral zone. Thus, while we observed potential for flexible compensation of heat through “hot” torpor, both populations showed patterns suggestive of limited potential to cope with acute microclimate changes deviating from their typically occupied roosts. Our study emphasizes that intraspecific variation among populations could be misleading when assessing species’ adaptive scopes, as variation may arise from genetic adaptation, developmental plasticity or phenotypic flexibility, all of which allow for compensatory responses at differing time scales. Disentangling these mechanisms and identifying the basis of variation is vital to make accurate predictions of species’ chances for persisting in ever rapidly changing habitats and climates.

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Section: Study Set-upmentioning

confidence: 99%

Section: Data Processing and Analysesmentioning

confidence: 99%

Section: Data Processing and Analysesmentioning

confidence: 99%

Section: Cave Bats Exposed To Experimental Forest Conditions (Wet Sea...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Limited Physiological Compensation in Response to an Acute Microclimate Change in a Malagasy Bat

et al. 2022

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Equivocal support for the climate variability hypothesis within a Neotropical bird assemblage

Pollock,

Rutt,

Cooper

et al. 2023

Ecology

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The climate variability hypothesis posits that an organism's exposure to temperature variability determines the breadth of its thermal tolerance and has become an important framework for understanding variation in species' susceptibilities to climate change. For example, ectotherms from more thermally stable environments tend to have narrower thermal tolerances and greater sensitivity to projected climate warming. Among endotherms, however, the relationship between climate variability and thermal physiology is less clear, particularly with regard to microclimate variation—small‐scale differences within or between habitats. To address this gap, we explored associations between two sources of temperature variation (habitat type and vertical forest stratum) and (1) thermal physiological traits and (2) temperature sensitivity metrics within a diverse assemblage of Neotropical birds (n = 89 species). We used long‐term temperature data to establish that daily temperature regimes in open habitats and forest canopy were both hotter and more variable than those in the forest interior and forest understory, respectively. Despite these differences in temperature regime, however, we found little evidence that species' thermal physiological traits or temperature sensitivity varied in association with either habitat type or vertical stratum. Our findings provide two novel and important insights. First, and in contrast to the supporting empirical evidence from ectotherms, the thermal physiology of birds at our study site appears to be largely decoupled from local temperature variation, providing equivocal support for the climate variability hypothesis in endotherms. Second, we found no evidence that the thermal physiology of understory forest birds differed from that of canopy or open‐habitat species—an oft‐invoked, yet previously untested, mechanism for why these species are so vulnerable to environmental change.

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State dependence of arousal from torpor in brown long-eared bats (Plecotus auritus)

et al. 2022

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To cope with periods of low food availability and unsuitable environmental conditions (e.g., short photoperiod or challenging weather), many heterothermic mammals can readily go into torpor to save energy. However, torpor also entails several potential costs, and quantitative energetics can, therefore, be influenced by the individual state, such as available energy reserves. We studied the thermal energetics of brown long-eared bats (Plecotus auritus) in the northern part of its distributional range, including torpor entry, thermoregulatory ability during torpor and how they responded metabolically to an increasing ambient temperature (Ta) during arousal from torpor. Torpor entry occurred later in bats with higher body mass (Mb). During torpor, only 10 out of 21 bats increased oxygen consumption (V̇O2) to a greater extent above the mean torpor metabolic rates (TMR) when exposed to low Ta. The slope of the torpid thermoregulatory curve was shallower than that of resting metabolic rate (RMR) during normothermic conditions, indicating a higher thermal insulation during torpor. During exposure to an increasing Ta, all bats increased metabolic rate exponentially, but the bats with higher Mb aroused at a lower Ta than those with lower Mb. In bats with low Mb, arousal was postponed to an Ta above the lower critical temperature of the thermoneutral zone. Our results demonstrate that physiological traits, which are often considered fixed, can be more flexible than previously assumed and vary with individual state. Thus, future studies of thermal physiology should to a greater extent take individual state-dependent effects into account.

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Disparate roost sites drive intraspecific physiological variation in a Malagasy bat

Cited by 8 publications

References 111 publications

Limited Physiological Compensation in Response to an Acute Microclimate Change in a Malagasy Bat

Limited Physiological Compensation in Response to an Acute Microclimate Change in a Malagasy Bat

Equivocal support for the climate variability hypothesis within a Neotropical bird assemblage

State dependence of arousal from torpor in brown long-eared bats (Plecotus auritus)

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