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Sources of yearly variation in gray bat activity in the Clinch River watershed, Virginia

March 1, 2023

The gray bat (Myotis grisescens) is a cave-obligate species that has been listed as federally endangered since 1976, following population declines from human disturbance at hibernation and maternity caves. However, with cave protection, most gray bat populations have increased. As part of a project examining bat use of transportation structures as day-roosts, we continuously acoustically monitored 12 riparian sites within the Clinch River Watershed of southwest Virginia from March through November, 2018–2020. We used 15 different landscape and weather-related variables in generalized linear mixed models to determine factors influencing gray bat presence and activity. Seasonal activity patterns were similar among years, but the number of nightly gray bat calls increased with each passing year, consistent with positive population trends observed at winter hibernacula. Year and average nightly temperatures were positively correlated with gray bat activity, as was, unexpectedly, average nightly wind speed. Total nightly precipitation, distance to the nearest hibernaculum in Tennessee, percent forested area within 2 km of a detector, mean elevation within 2 km of a detector, detector type, and amount of urban development within 2 km of a detector were negatively correlated with gray bat activity. Our findings show where and when gray bat presence is likely in southwest Virginia, thereby helping managers avoid negative impacts from activities such as bridge repair or replacement and planning of future monitoring to track population trends.

Publication Year 2023
Title Sources of yearly variation in gray bat activity in the Clinch River watershed, Virginia
Authors H. Taylor, K. Powers, W. Orndorff, Rick Reynolds, E.M. Hallerman, W. Mark Ford
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of the Southeastern Association of Fish and Wildlife Agencies
Index ID 70262830
Record Source USGS Publications Warehouse
USGS Organization Coop Res Unit Leetown
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