Long-term patterns of cave-exiting activity of hibernating bats in western North America

Abstract

Understanding frequency and variation of cave-exiting activity after arousal from torpor of hibernating bats is important for bat ecology and conservation, especially considering white-nose syndrome. In winter from 2011 to 2018, we acoustically monitored, and counted in hibernacula, two species of conservation concern—western small-footed myotis (Myotis ciliolabrum) and Townsend’s big-eared bats (Corynorhinus townsendii)—in 9 caves located in important habitat for these species in western North America. We investigated if cave-exiting activity differed by species, cave, number of hibernating bats, moon phase, and weather variables. Both species exited hibernacula during all winter months, but most activity occurred in March followed by November. Although we counted almost 15 times more Townsend’s big-eared bats during hibernacula surveys, we documented western small-footed myotis exiting caves 3 times more than Townsend’s big-eared bats. Cave-exiting activity increased with increasing number of hibernating bats, but more so for western small-footed myotis. Both species of bats were active during warm weather and low wind speeds. Western small-footed myotis were more active during colder temperatures, higher wind speeds, and greater change in barometric pressure than Townsend’s big-eared bats. Our results provide a long-term dataset of cave-exiting activity after arousal from torpor during hibernation for these species before the arrival of white-nose syndrome.

Predicting habitat suitability for Townsend's big‐eared bats across California in relation to climate change

“…Our results support precipitation as an important factor for this species at multiple life phases. Elevation is another important variable contributing to the hibernacula models, with suitability increasing with elevation up to ~2750 m, consistent with previous studies of C. townsendii reporting the species hibernating at >1500 m (Gillies et al, 2014 ; Harris et al, 2019 ; Hayes et al, 2011 ; Szewczak et al, 1998 ; Whiting et al, 2021 ). However, recent modeling approaches predict higher suitability for C. townsendii hibernacula at elevations <1000 m. Differences in predicted elevation are likely due to differences in occurrence data, environmental predictor variables, study extent (including latitude), and modeling techniques used.…”

“…High humidity within hibernacula reduces evaporative water loss during hibernation (Speakman & Thomas, 2003). Our results support precipitation as an important factor for this species at reporting the species hibernating at >1500 m (Gillies et al, 2014;Harris et al, 2019;Hayes et al, 2011;Szewczak et al, 1998;Whiting et al, 2021). However, recent modeling approaches predict higher suitability for C. townsendii hibernacula at elevations <1000 m.…”

Effect of Fungi Presence on Wing Morphometry and Flight Behaviour in the Common Pipistrelle Bats (Pipistrellus pipistrellus)

“…The observed patterns in the distribution of minimum angle measurements for both left and right wings are in line with recent findings in the literature. as it has been reported that, the bats with fungal infestation exhibited restricted wing flexibility, leading to altered wing angles [40] . Our results align with this, as we observed a more widespread distribution of minimum angles in wings without fungal infestation, indicating greater morphological variability.…”

How weather triggers the emergence of bats from their subterranean hibernacula

“…Both species are of similar size and weight and form small to medium-sized nursery colonies in trees and buildings. It is suggested that small bat species may need to wake up more frequently to drink during hibernation due to an unfavorable surface-to-volume ratio 55 . Once an individual bat is active, it may have a high motivation to leave the hibernaculum to forage 56 and relocate to summer habitats.…”