Winter activity of boreal bats

Blomberg, Anna; Vasko, Ville; Meierhofer, Melissa B.; Johnson, Joseph S.; Eeva, Tapio; Lilley, Thomas M.

doi:10.1007/s42991-021-00111-8

Cited by 17 publications

(7 citation statements)

References 51 publications

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“…Even in winter, prey is available, albeit in low abundance, and is exploited by Plecotus auritus 58 , 59 . The sensitivity to weather with increased prey availability in winter and the spontaneous response to exploit this winter food has been found for Plecotus auritus from different parts of its range 60 . So food availability and mating season in late winter increases activity over a long period of time and reduces synchronization.…”

Section: Discussionmentioning

confidence: 94%

How weather triggers the emergence of bats from their subterranean hibernacula

Koch

Manecke

Burgard

et al. 2023

Sci Rep

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Hibernation is one of the most important behaviours of bats of the temperate zone. During winter, when little food or liquid water is available, hibernation in torpor lowers metabolic costs. However, the timing of emergence from hibernation is crucial for the resumption of the reproductive process in spring. Here, we investigate the spring emergence of six bat species or pairs of bat species of the genera Myotis and Plecotus at five hibernation sites in Central Europe over 5 years. Using generalized additive Poisson models (GAPMs), we analyze the influence of weather conditions (air and soil temperature, atmospheric pressure, atmospheric pressure trend, rain, wind, and cloud cover) as predictors of bat activity and separate these extrinsic triggers from residual motivation to emerge from hibernation (extrinsic factors not studied; intrinsic motivation). Although bats in a subterranean hibernaculum are more or less cut off from the outside world, all species showed weather dependence, albeit to varying degrees, with air temperature outside the hibernaculum having a significant positive effect in all species. The residual, potentially intrinsic motivation of species to emerge from their hibernacula corresponds to their general ecological adaptation, such as trophic specialization and roosting preferences. It allows the definition of three functional groups (high, medium and low residual activity groups) according to the degree of weather dependence of spring activity. A better knowledge of the interplay of extrinsic triggers and residual motivation (e.g., internal zeitgebers) for spring emergence will help to understand the flexibility of a species to adapt to a changing world.

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Section: Discussionmentioning

confidence: 94%

How weather triggers the emergence of bats from their subterranean hibernacula

Koch

Manecke

Burgard

et al. 2023

Sci Rep

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show abstract

“…Notably, buildings and tree crevices serve as recognized summer roosting sites for boreal bats (Rydell, 1989; Marnell & Pretznick; Suominen et al, 2023), whereas boulder fields lack documented use during this period. Nonetheless, certain records indicate E. nilssonii occupying similar habitats in early spring, late autumn, and winter (Michaelsen et al, 2013; Fritzén & Hägg, 2020; Blomberg et al, 2021), suggesting these areas could serve as suitable overwintering sites. The utilization of both summer roost types and potential overwintering sites implies potential T a variations in these roosts.…”

Section: Discussionmentioning

confidence: 99%

Thermoregulation and Diurnal Roost Selection of Boreal Bats During Pre-Hibernation Period

Suominen,

Fritzén,

Fjelldal

et al. 2024

Preprint

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Living in a seasonal environment poses challenges for small mammals, such as bats, reliant on insects as their primary food source. Bats may adeptly navigate these energetic challenges by reducing their metabolism and body temperature, entering a state of torpor. Particularly during the winter, bats remain torpid for extended periods, but are dependent on sufficient energy reserves to survive until spring. With the onset of autumn and declining temperature, bats face the challenge of building their fat deposits during a time of decreasing food availability. Bats may therefore transition to cooler roosts to initiate torpor, thereby reducing energy expenditure. However, little is still known about torpor use or roost selection by bats in autumn. This study explores the factors influencing roost selection and torpor use and duration in two bat species during this critical transition period between the breeding and overwintering season. We show that date in autumn is a stronger driver of torpor use than prevailing ambient temperature, and that bats employ specific strategies in which they first increase daytime torpor use before also increasing the use of night-time torpor during the pre-hibernation fattening period, most likely to facilitate rapid fat accumulation. Notably, bats commenced night-time torpor use after spending entire days in torpor. These findings underscore the dynamic nature of torpor and the energy-saving strategies employed during the crucial pre-hibernation period, marking the transition from summer to winter.

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“…Moreover, these issues similarly affect the manual validation of acoustic recordings, whereas validation from camera trap images is readily feasible. Despite these shortcomings, acoustic surveys represent an important method for wide‐spread surveillance and scouting and remain one of the only methods for monitoring hibernation sites where light barriers cannot be readily installed and that cannot be visually counted (e.g., complex sites with many large entrances, rock crevices and piles; Blomberg et al., 2021).…”

Section: Discussionmentioning

confidence: 99%

BatNet: a deep learning‐based tool for automated bat species identification from camera trap images

Krivek,

Gillert,

Harder

et al. 2023

Remote Sens Ecol Conserv

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Automated monitoring technologies can increase the efficiency of ecological data collection and support data‐driven conservation. Camera traps coupled with infrared light barriers can be used to monitor temperate‐zone bat assemblages at underground hibernacula, where thousands of individuals of multiple species can aggregate in winter. However, the broad‐scale adoption of such photo‐monitoring techniques is limited by the time‐consuming bottleneck of manual image processing. Here, we present BatNet, an open‐source, deep learning‐based tool for automated identification of 13 European bat species from camera trap images. BatNet includes a user‐friendly graphical interface, where it can be retrained to identify new bat species or to create site‐specific models to improve detection accuracy at new sites. Model accuracy was evaluated on images from both trained and untrained sites, and in an ecological context, where community‐ and species‐level metrics (species diversity, relative abundance, and species‐level activity patterns) were compared between human experts and BatNet. At trained sites, model performance was high across all species (F1‐score: 0.98–1). At untrained sites, overall classification accuracy remained high (96.7–98.2%), when camera placement was comparable to the training images (<3 m from the entrance; <45° angle relative to the opening). For atypical camera placements (>3 m or >45° angle), retraining the detector model with 500 site‐specific annotations achieved an accuracy of over 95% at all sites. In the ecological case study, all investigated metrics were nearly identical between human experts and BatNet. Finally, we exemplify the ability to retrain BatNet to identify a new bat species, achieving an F1‐score of 0.99 while maintaining high classification accuracy for all original species. BatNet can be implemented directly to scale up the deployment of camera traps in Europe and enhance bat population monitoring. Moreover, the pretrained model can serve as a baseline for transfer learning to automatize the image‐based identification of bat species worldwide.

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Winter activity of boreal bats

Cited by 17 publications

References 51 publications

How weather triggers the emergence of bats from their subterranean hibernacula

How weather triggers the emergence of bats from their subterranean hibernacula

Thermoregulation and Diurnal Roost Selection of Boreal Bats During Pre-Hibernation Period

BatNet: a deep learning‐based tool for automated bat species identification from camera trap images

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