First record of tree cavity roosting in frosted myotis (Myotis pruinosus)

Frosted myotis (Myotis pruinosus) is a rare and little-known bat, listed as Endangered by the IUCN. Although it inhabits forests and has been suspected to roost in tree cavities, all roosting individuals found to date were in caves. Hereby, I report a discovery of an individual roosting in a tree cavity made by Japanese pygmy woodpecker (Picoides kizuki), in a large pine tree in an old-growth mixed forest in Nikko National Park, Japan. This observation confirms that frosted myotis roosts in tree cavities but does not support the hypothesis that dependence on larger cavities explains the species’ affinity with old-growth forests.