Capturing endangered endemic Okinawan bats with acoustic lures

Abstract

Many rare island endemic bats are highly threatened but poorly studied, due partly to the difficulty of capturing them. We used acoustic lures playing synthesised bat social calls on Okinawa Island, Japan, to improve capture success for two of the country’s most endangered endemic bats: the Ryukyu tube-nosed bat (Murina ryukyuana) and Yanbaru whiskered bat (Myotis yanbarensis). First, we systematically tested the effectiveness of acoustic lures in a paired trial. Acoustic lures increased M. ryukyuana capture rates ten-fold. A sequence of stimuli based on congeneric calls appeared to be more effective than one based on calls of other genera. No M. yanbarensis were caught during the trial. We then continued to use lures during capture surveys across 50 sites in 2017 – 2019. Murina ryukyuana (n = 46) and M. yanbarensis (n = 17) were caught at 58% and 12% of survey sites, respectively. For Okinawa, these represent the first captures of M. yanbarensis reported in two decades and an eight-fold increase in the number of M. ryukyuana reported. Capture rates were higher using lures, fluctuated seasonally, and were probably biased towards males. We conclude that using acoustic lures will facilitate further study, and therefore conservation, of these unique island endemic bats. Acoustic lures would improve capture rates for standardised surveys across the ranges of M. ryukyuana and M. yanbarensis. Such surveys are necessary to assess the relative abundance of each population and identify conservation priorities. Acoustic lures are also likely to improve capture rates for other rare Murina species, including many endemic to small areas.