Entering torpor can yield significant energy savings for temperate-zone bats but can be costly for reproductive females by slowing fetal development and reducing milk production. We studied western long-eared bats (Myotis evotis (H. Allen, 1864)) in the Rocky Mountains of Alberta to test the hypothesis that different costs of torpor result in different patterns of thermoregulation and roosting behaviour for reproductive and nonreproductive females. We radio-tracked bats to monitor body temperatures and locate roosts. We took roost measurements and inserted temperature data loggers to measure roost microclimate. Bats entered torpor frequently, but nonreproductive females spent longer periods in torpor, had lower minimum body temperatures, and entered deep torpor more often than reproductive females did, supporting the hypothesis that entering torpor is more costly for reproductive individuals. Roosts were located mainly in rock fields on steep, open, south-facing slopes. Reproductive females roosted in crevices between rocks located above or on the surface of the ground. Roosts warmed rapidly and reached warm daytime temperatures. Females roosted alone during pregnancy but formed small colonies within roosts during lactation when ambient conditions were cooler. Clustering may reduce thermoregulatory costs for both adults and young. Nonreproductive females roosted mainly alone in crevices in the ground. These roosts had cooler, more stable microclimates, allowing females to enter deeper bouts of torpor and remain torpid longer.

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Quantitative methods for species identification are commonly used in acoustic surveys for animals. While various identification models have been studied extensively, there has been little study of methods for selecting calls prior to modeling or methods for validating results after modeling. We obtained two call libraries with a combined 1556 pulse sequences from 11 North American bat species. We used four acoustic filters to automatically select and quantify bat calls from the combined library. For each filter, we trained a species identification model (a quadratic discriminant function analysis) and compared the classification ability of the models. In a separate analysis, we trained a classification model using just one call library. We then compared a conventional model assessment that used the training library against an alternative approach that used the second library. We found that filters differed in the share of known pulse sequences that were selected (68 to 96%), the share of non-bat noises that were excluded (37 to 100%), their measurement of various pulse parameters, and their overall correct classification rate (41% to 85%). Although the top two filters did not differ significantly in overall correct classification rate (85% and 83%), rates differed significantly for some bat species. In our assessment of call libraries, overall correct classification rates were significantly lower (15% to 23% lower) when tested on the second call library instead of the training library. Well-designed filters obviated the need for subjective and time-consuming manual selection of pulses. Accordingly, researchers should carefully design and test filters and include adequate descriptions in publications. Our results also indicate that it may not be possible to extend inferences about model accuracy beyond the training library. If so, the accuracy of acoustic-only surveys may be lower than commonly reported, which could affect ecological understanding or management decisions based on acoustic surveys.

The costs and benefits of torpor may vary across the range of widespread heterothermic species, resulting in different thermoregulatory patterns and other behaviours for individuals inhabiting different environments. We compared torpor use and roosting behaviour for rock-roosting populations of western longeared bats Myotis evotis living in the mountains and prairies of Alberta, Canada. We monitored body temperatures and located roosts for pregnant and lactating females using radio-telemetry. We also took roost measurements, and assessed roost microclimate using temperature dataloggers. Females in the mountains entered torpor less frequently and spent less time in torpor than bats in the prairies, supporting our hypothesis that reproductive time constraints in the mountains outweigh the benefits of torpor. Alternatively, increased torpor use in the prairies may be attributed to a greater need for water conservation. Females in the mountains minimized thermoregulatory costs and maintained homeothermy by selecting exposed roosts with warm microclimates during pregnancy, and then switching to clustering with other individuals during lactation when conditions were cooler. In the prairies, females roosted alone in cooler, less exposed roost types, which facilitate the use of torpor. Our results illustrate the importance of considering geographic variation in behaviour across the range of a species.