Roosting Ecology and Behavior of the Solitary and Foliage-roosting Hawaiian Hoary Bat (Lasiurus cinereus semotus)

Abstract

The Hawaiian hoary bat (Lasiurus cinereus semotus) is a Federally and State of Hawai‘i listed endangered species and is the only extant, native, terrestrial mammal in the Hawaiian archipelago. With increasing threats, especially from wind energy expansion and potential habitat loss in Hawai‘i, it is critical to gain a more complete understanding of the life history and ecology of this elusive species in order to better inform conservation and management decisions. This study was motivated by the lack of published data examining the diurnal roost characteristics and roosting behavior of this species. Hawaiian hoary bats were captured, radio-tagged and tracked to diurnal roosting locations on the east side of Hawai‘i Island from May 2018 to December 2019. A total of 38 bats were tracked to 52 roost stands and 18 of those bats were located in 24 roost trees. Bats were confirmed at 15 perches within the 24 roost trees. Bats used diurnal roosts in a variety of tree species and in an assortment of habitat stand types including native and non-native habitats. Statistically significant differences were found in both height and diameter at breast height (DBH) between roost trees and randomly sampled trees. Specifically, roost trees were generally larger in both height and DBH than random trees and female bats selected roost trees that were larger in height and with a greater percent canopy cover compared to roost trees selected by male bats. Diurnal roost video-monitoring was conducted at two separate sites in Hilo, Hawai‘i during the 2017 and 2018 reproductive seasons. A total of 114 hours, 50 minutes and 21 seconds (114:50:21) of video imagery was observed and analyzed. Observations of solitary bats accounted for a total of 86:38:17 video-hours while maternity roost observations accounted for a total of 28:12:08 video-hours. An ethogram of behavior at diurnal roosts was created from observations and represents the first detailed description of the behavior of L. c. semotus at diurnal roosts.