Using passive integrated transponder (PIT) tags to monitor and research bats: Applications, benefits, and limitations

Worldwide declines of bat populations underscore the value of developing and refining survey tools to assess and monitor population statuses and dynamics. Passive integrated transponder (PIT) tags can be an effective marking technique, facilitating the monitoring of individual bats at roost sites by using radio frequency (RFID) readers and antennas. We detail 5 ongoing studies, discuss the rationale for our study designs, and offer recommendations for monitoring and researching bats with PIT tags that are broadly applicable across species and locations. Using data from RFID readers, we show how population parameters can be precisely estimated across space and time, while improving our understanding of bat ecology and vulnerability to threats. We discuss PIT-tag loss as a potential limitation that varies across species, sex, and season, present minimum loss rates from 2 studies, and describe consequences and techniques to ameliorate this issue. Overall, integrating PIT tags with autonomous RFID readers and antennas provides a powerful survey method for monitoring, researching, and conserving bat populations.