Translocation of lesser short-tailed bats to Kapiti Island, New Zealand: release site suitability and post-release monitoring

Summary

The lesser short-tailed bat (Mystacina tuberculata), Vulnerable and represented in the Tararua Ranges by a small, genetically distinct, Nationally Critical population, was translocated by New Zealand's Department of Conservation to pest-free Kapiti Island to secure the lineage, since previous bat translocations elsewhere had failed, often from homing behavior. To reduce that risk, DOC released captive-reared juveniles unimprinted on the original site, held them two months in an on-site aviary to encourage imprinting on the release location, and provided supplementary food and roosts afterward. University of Auckland researchers first assessed roosting habitat, estimating thousands of suitable cavity-bearing trees despite much of the island's forest still regenerating, then conducted a year of post-release monitoring on 20 released bats using video surveillance, mark-recapture, and radio-tagging of two individuals. Ten bats were recorded in the aviary three days after release, nine were marked and confirmed alive eight months later, and both radio-tagged bats remained on the island, meeting the study's short-term survival benchmarks. However, all bats examined eight months post-release showed scabbing, infected skin and balding of unknown cause; DOC later re-released the bats but permanently returned them to captivity when the disease recurred, and a veterinary team could not determine its cause. Major difficulties included the species' vagility making comprehensive monitoring impossible and small sample sizes obscuring condition trends. The project rates itself a Failure, since the translocation ultimately could not be sustained despite promising initial survival evidence.