Discriminating predation attempt outcomes during natural foraging using the post-buzz pause in the Japanese large-footed bat, Myotis macrodactylus

Bats emit a series of echolocation calls with an increasing repetition rate (the terminal buzz) when attempting to capture prey. This is often used as an acoustic indicator of prey-capture attempts. However, because it is directly linked to foraging efficiency, predation success is a more useful measure than predation attempts in ecological research. The characteristics of echolocation calls that consistently signify predation success across different situations have not been identified. Owing to additional influencing factors, identification of these characteristics is particularly challenging for wild bats foraging in their natural environment compared with those in flight chambers. This study documented the natural foraging behavior of wild Japanese large-footed bats (Myotis macrodactylus) using synchronized acoustic and video recordings. From the video recordings, we could assign 137 attacks to three outcome categories: prey captured (51.8%), prey dropped (29.2%) and failed attempt (19%). Based on previous indications from laboratory studies that the length of the silent interval following the terminal buzz (post-buzz pause) might reflect the prey-capture outcome, we compared post-buzz pause durations among categories of attack outcomes. The post-buzz pause was longest in the case of successful capture, suggesting that the length of the post-buzz pause is a useful acoustic indicator of predation success during natural foraging in M. macrodactylus. Our finding will advance the study of bat foraging behavior using acoustic data, including estimations of foraging efficiency and analyses of feeding habitat quality.