English

Abstract

The purpose of this study was to determine whether inactive mine features on privately owned lands and lands administered by the Bureau of Land Management (BLM) in Pima County, in southeastern Arizona (the study area), were being used by bats. External pre-screening surveys of 60 inactive mine features were completed in March 2012, and it was determined that 23 of these sites had the potential to provide roosts for bats. Passive external portal acoustic and visual surveys of these 23 features were completed using AnaBat acoustic detectors and infrared trail cameras from May through mid-October 2012. Acoustic survey data were analyzed, and 10 species of bats were identified. Bat species were acoustically detected at all 23 sites but were only visually detected at two sites. Acoustically, bat activity and species richness were highest in the spring and lowest in the fall. The two most common species, canyon bat (Parastrellus hesperus) and Mexican free-tailed bat (Tadarida brasiliensis), accounted for more than 50% of all the survey data. Ten sites accounted for more than 75% of all bat activity. Species richness was highest at two sites, with seven species detected at each site, and was lowest at two sites, where only one or two species were detected. Two species identified as species of concern under the Endangered Species Act (ESA) - western small-footed myotis (Myotis ciliolabrum) and Yuma myotis (M. yumanensis) - were acoustically detected at 15 and three sites, respectively. Two BLM-sensitive species (also identified as species of concern under the ESA) - Townsend's big-eared bat (Corynorhinus townsendii) and cave myotis (M. velifer) - were acoustically detected at 10 sites (seven of which are on BLM lands) and seven sites (three of which are on BLM lands), respectively. Although no bats were detected in any photos or videos, when biologists visually monitored each site, bats occasionally were seen flying in the study area around sunset, but only one bat was seen exiting from an inactive mine site. Townsend's big-eared bats were observed roosting in two adits on BLM-administered lands during the fall. No major bat roosts or no threatened or endangered bat species (e.g., lesser long-nosed bats (Leptonycteris curasoae yerbabuenae)) were detected through these surveys.