Timing of the evening emergence of Hilgendorf’s tube-nosed bat (Murina hilgendorfi) in relation to roost type and season

Like for many species, the timing of evening emergence of bats is an important behavioral aspect that affects their fitness and has been studied in various bat species. However, little is known about emergence timing of solitary bats that frequently switch day roosts, because they are difficult to observe. In this study, I examined the emergence timing of Hilgendorf’s tube-nosed bats (Murina hilgendorfi), which are solitary and frequently switch roosts, in relation to roost type and season over six years in Hayakawa, central Japan. The results show that the bats emerged after dusk when the light was weak. Later emergence may be related to the habits of this species, such as their solitary lifestyle, slow flight speed, and gleaning foraging strategy, which may enhance predation risk. Individuals roosting in dead foliage and on the outer wall of a building situated in closed forests emerged significantly earlier than those roosting in an old mine and tunnel located in open environments, suggesting that vegetation cover and/or lower predictability of roost location provide security for bats. Bats emerged progressively earlier from late spring (preparturition) to early autumn (late lactation or post-lactation), suggesting that the reproductive status of females or the growth stage of pups may influence emergence timing. To my knowledge, this study provides the first record of the emergence timing of Hilgendorf’s tube-nosed bat, and suggests that predation risk may impact the bats’ emergence behavior.