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

Jericho C Whiting,Ken Aho,Bill Doering,Jason Rich

doi:10.1038/s41598-021-87605-0

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.

Highlights

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
White-nose syndrome is caused by the cold-adapted fungus Pseudogymnoascus destructans[30,31]
Survival of hibernating bats with white-nose syndrome may be influenced by increased arousal and energy expenditure, premature depletion of fat reserves, which can lead to emergence from caves too early and starvation[34,38]

Summary

Introduction

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. Disturbances to bats include lights, noise, vandalism, camping, and caving excursions[20,23,24] These disturbances can cause bats to arouse from torpor, elevate body temperatures, and use stored energy reserves; potentially reducing winter survival[20,23,25]. This fungus invades the integumentary system of infected bats causing tissue damage, increased metabolic rate, and water loss because of excessive wing damange[27,32,33] Hibernating bats with this disease arouse more often, use more energy because of elevated metabolic rates during torpor, exhibit higher rates of evaporative water loss[32,34,35], exit caves more o ften[36,37], and potentially have reduced reproductive s uccess[38]. A disease occurring in eastern North America, white-nose syndrome is documented in the western U SA41

Methods

Results

Conclusion