Bat box monitoring: testing the efficacy of eDNA to confirm box use

Abstract

ABSTRACT Bat boxes can be employed to provide short-term mitigation for the loss of trees with bat roost potential. Traditionally bat box utilisation (by long-tailed bats) has been difficult to confirm in NZ, partly due to a lack of published survey techniques to confirm bat box utilisation when bats are not present at the time of sampling. While environmental deoxyribonucleic acid (eDNA) has been widely applied as a biomonitoring tool, it has not been used previously in the context of bat box surveys in New Zealand. Here we present a method for collecting eDNA from bat boxes using swabs and test the efficacy of eDNA in validating bat box utilisation as confirmation of roosting. Bat boxes were deployed by the Hamilton City Council as part of the bat mitigation strategy for the Southern Links Project in southern Hamilton. The eDNA method confirmed a total of 25 boxes out of the 73 (34%) included in this study were being utilised by long-tailed bats. The results indicate that eDNA can be applied with confidence to demonstrate box use, even at very low and infrequent occupancy rates.