Behavioral response of bats to passive integrated transponder tag reader arrays placed at cave entrances

Abstract

An increasingly popular mark-recapture method to study the ecology of bats is the use of passive integrated transponder (PIT) tags. Deployment of PIT reader arrays at entrances to caves and mines can yield insight into bat behavior during swarming, winter activity, and emergence. This application has the potential to address questions about bat activity at cave and mine entrances in response to white-nose syndrome or bat seasonal movements; however, no studies have examined the response of bats to these arrays. We describe bat response to placement of PIT tag reader arrays using camcorders and supplemental infrared illuminators at three cave entrances near Bloomington, Indiana, during spring 2006. A random subset of 5-min periods was viewed and bat behavior was classified. Circling represented >70% of all behavior noted for two caves but only represented approximately 30% of behavior at the third cave. Proportions of observed activity that resulted in contacts or landings were consistently low across the three caves (x̄ = 1.34%; range 0.5-3.0%), with most contacts causing bats to simply change course and fly away. Based on our observations, positioning reader PIT tag reader arrays at cave entrances to passively recapture PIT tags does not limit bat movements. However, video monitoring during initial sampling efforts of future projects should be conducted to verify appropriate placement and configuration of PIT tag reader arrays. This research provides data illustrating the lack of significant impact in using PIT tag reader arrays at cave entrances, thereby opening up the potential use of this technology to address issues of bats ecology that cannot be obtained with other marking techniques.