Bat use of abandoned mines throughout Nevada

Abstract

Abandoned mines offer important roosting habitat for several species of bats throughout the western United States. Currently, abandoned mine reclamation programs are tasked with closing abandoned mines to ameliorate safety, health, and environmental hazards found in and around these sites. Without appropriate pre‐closure evaluations to determine use of mine workings prior to closure, bats that depend on abandoned mines may be negatively impacted. To mitigate impacts of abandoned mine reclamation on bats, surveyors typically conduct pre‐closure biological evaluations and recommend wildlife compatible closures (e.g., bat gates) for ecologically important sites. Due to hazardous conditions found in many abandoned mines, internal surveys cannot always be conducted, and external surveys are not reliable for determining underground habitat or inferring past, future, or potential use of mines by bats when they are absent during external surveys. The purpose of our study was to use internal mine surveys to examine relationships between abandoned mine use by bats and characteristics of the mine and landscape, including portal area and shape, number of portals, mine depth, elevation, proximity to water and land use type. We found that surface features including land use type, distance to water, and elevation were associated with bat use, as were several mine features including depth of workings and portal shape. To best conserve sensitive species of bats, it is essential that pre‐closure biological evaluations be as detailed as possible to enhance biological understanding of species' roosting associations and distribution throughout the landscape. Further information will best facilitate development of ecologically sound closure recommendations for abandoned mine openings.