A five-year study of Hawaiian hoary bat (Lasiurus cinereus semotus) occupancy on the island of Hawai`i

Using acoustic recordings of the vocalizations of the endangered Hawaiian hoary bat (Lasiurus
cinereus semotus) collected over a five-year period (2007–2011) from 25 survey areas across
the island of Hawai`i, we modeled the relationship between habitat attributes and bat
occurrence. Our data support the conclusion that hoary bats concentrate in the coastal lowlands
of Hawai`i during the breeding season, May through October, and migrate to interior highlands
during the winter non-breeding season. Highest occupancy peaked on the Julian date 15
September across the five-year average and during the season of fledging by the young of the
year. Although the Hawaiian hoary bat is a habitat generalist species and occurs from sea level
to the highest volcanic peaks on Hawai`i, there was a significant association between
occupancy and the prevalence of mature forest cover. Trends in occupancy were stable to
slightly increasing during the breeding season over the five years of our surveys.