Calling home: do acoustic lures and novel roosts attract the rare Florida Bonneted Bat ( <i>Eumops floridanus</i> )?

Abstract Increasing habitat loss poses a threat to bats that roost in slowly maturing trees. Artificial roosts are popular for providing short-term offsets for the loss of trees used by bats; however, colonization can be slow. Identifying methods to attract bats to artificial roosts could be important for improving this offsetting strategy. We deployed 3 paired clusters of artificial roosts in Florida, United States, targeting the endangered Florida Bonneted Bat (Eumops floridanus; hereafter bonneted bat). Each cluster contained 3 roost designs that differ in internal temperature: a flat-faced chamber box, a standard rocket box, and a rocket box with an external water jacket (EJW) (18 artificial roosts in total). For 1 roost cluster within each pair, an ultrasonic speaker broadcasted pre-recorded bonneted bat echolocation calls. From March 2021 to October 2022, we used spotlight checks, emergence counts, and acoustic detectors to quantify bat occupancy and relative bat activity. We found no effect of the acoustic lure on the presence of bonneted bat acoustic activity at roost clusters; however, we found a seasonal trend with a greater probability of bonneted bat acoustic activity in March and April. Sixteen months after deployment, a single bonneted bat took up residence in one EJW roost. Thirteen months after the end of the study, a harem colony of bonneted bats was using this same roost. We highlight that short-term projects may be ineffective at assessing the efficacy of an artificial roost design for rare bats and that more work is needed to understand the context of echolocation calls used in acoustic lures.