CONSERVATION BIOLOGY OF OKINAWA'S RARE FOREST BATS

The Ryukyu tube-nosed bat (Murina ryukyuana) and Yanbaru whiskered bat (Myotis yanbarensis) are of Japan’s rarest and least understood bat species. Discovered in the Yanbaru Forest of Okinawa Island, these two bat species only exist on three islands: Okinawa, Tokunoshima, and Amami-Oshima.

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Our research goal is to provide the information necessary to design conservation guidelines for these two small forest bats. Both species are considered at risk of extinction by the International Union for the Conservation of Nature (IUCN) and the Japanese Ministry of Environment, with the Yanbaru whiskered bat being considered “Critically Endangered”. However, due to a shortage of research, we know very little about the lives of these bats and therefore, very little about how best to conserve them. To help fill this knowledge gap, we’ve been busy trying to answer three questions fundamental to the conservation of these bats:

1. What kind of roosts do they use?

2. What do they eat?

3. Where are they (what kind of habitats do they prefer)? 

It hasn’t been easy to catch these rare bats, but we have been steadily getting closer to answering our research questions with help from acoustic lures, radio-tracking, DNA barcoding, and automated ultrasonic recorders. In February 2018, we managed to finally capture the Yanbaru whiskered bat, reporting it for the first time on Okinawa since the species was discovered 22 years ago. We have caught several more Yanbaru whiskered bats since then, but it seems to be much rarer than the Ryukyu tube-nosed bat and we want to figure out why.

We are currently in the process of analyzing and publishing our results from just over two years of field research on the Ryukyu tube-nosed bat and Yanbaru whiskered bat. From our roost-tracking, we’ve figured out that the Ryukyu tube-nosed bat usually roosts solitarily in leaves but will also use tree cavities, especially when rearing pups. On the other hand, the Yanbaru whiskered bat appears to need tree cavities along streams and gulch bottoms in old-growth forests. Some other highlights include finding the first examples of Yanbaru whiskered bat breeding roosts, and figuring out that the Ryukyu tube-nosed bat will sometimes feed on the ground (quite unusual for a bat)!

Below is a video by Okinawa TV, as part of their environmental series, that gives a sense of the day to day (or night to night) roost tracking and bat capture survey work we've been doing in Yambaru. (Sorry, it's all in Japanese.)

Study kindly supported by the following funders

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