Coordinated Control of Acoustical Field of View and Flight in Three-Dimensional Space for Consecutive Capture by Echolocating Bats during Natural Foraging

Abstract

Echolocating bats prey upon small moving insects in the dark using sophisticated sonar techniques. The direction and directivity pattern of the ultrasound broadcast of these bats are important factors that affect their acoustical field of view, allowing us to investigate how the bats control their acoustic attention (pulse direction) for advanced flight maneuvers. The purpose of this study was to understand the behavioral strategies of acoustical sensing of wild Japanese house bats Pipistrellus abramus in three-dimensional (3D) space during consecutive capture flights. The results showed that when the bats successively captured multiple airborne insects in short time intervals (less than 1.5 s), they maintained not only the immediate prey but also the subsequent one simultaneously within the beam widths of the emitted pulses in both horizontal and vertical planes before capturing the immediate one. This suggests that echolocating bats maintain multiple prey within their acoustical field of view by a single sensing using a wide directional beam while approaching the immediate prey, instead of frequently shifting acoustic attention between multiple prey. We also numerically simulated the bats’ flight trajectories when approaching two prey successively to investigate the relationship between the acoustical field of view and the prey direction for effective consecutive captures. This simulation demonstrated that acoustically viewing both the immediate and the subsequent prey simultaneously increases the success rate of capturing both prey, which is considered to be one of the basic axes of efficient route planning for consecutive capture flight. The bat’s wide sonar beam can incidentally cover multiple prey while the bat forages in an area where the prey density is high. Our findings suggest that the bats then keep future targets within their acoustical field of view for effective foraging. In addition, in both the experimental results and the numerical simulations, the acoustic sensing and flights of the bats showed narrower vertical ranges than horizontal ranges. This suggests that the bats control their acoustic sensing according to different schemes in the horizontal and vertical planes according to their surroundings. These findings suggest that echolocating bats coordinate their control of the acoustical field of view and flight for consecutive captures in 3D space during natural foraging.

Organization of projection from brainstem auditory nuclei to the inferior colliculus of Japanese house bat (Pipistrellus abramus)

“…Furthermore, by analyzing the distribution of retrogradely labeled cells inside the IC, we identified cell types that make long‐range intrinsic connection inside the IC. Although this species have been used frequently on biosonar studies (Fujioka et al., 2014; Sumiya, Fujioka, Motoi, Kondo, & Hiryu, 2017; Takahashi et al., 2014; Yamada, Hiryu, & Watanabe, 2016), the information about the organization of auditory pathways of this species has not been reported except for a single unit recording study from the IC (Goto, Hiryu, & Riquimaroux, 2010). Therefore, our study will give new neuroethological insights on biosonar.…”

Acoustic localization of terrestrial wildlife: Current practices and future opportunities

“…Twenty‐four studies quantified the amplitude or directionality of animal sounds, using localization to account for the animal's distance or position in relation to the microphone; this method was especially common in studies of bats (e.g., Holderied & Helversen, 2003; Jakobsen, Olsen, & Surlykke, 2015; Lewanzik & Goerlitz, 2018), but was also used to study elephants (Hedwig, DeBellis, & Wrege, 2018; Wrege, Rowland, Keen, & Shiu, 2017) and birds (Dantzker, Deane, & Bradbury, 1999; Patricelli, Dantzker, & Bradbury, 2007, 2008). Fourteen studies used localization to select subsets of sounds for further acoustic analysis, such as selecting calls from flights where bats approached the microphone array at a desired angle (e.g., Motoi, Sumiya, Fujioka, & Hiryu, 2017; Sumiya, Fujioka, Motoi, Kondo, & Hiryu, 2017). Fourteen studies localized multiple individuals simultaneously to study their behavior during interactions, such as interactions between pairs or rivals (e.g., Foote, Fitzsimmons, Mennill, & Ratcliffe, 2008; Mennill & Vehrencamp, 2008).…”

Selection of foraging and commuting habitats of the greater horseshoe bat, revealed by high-resolution GPS-tracking

“…Most bat species, except for a part of Pteropodidae, select flight routes based on information obtained by echolocation [3]. Since their echolocation calls do not propagate usually over large distances in air (< 10 m [4]), most studies have focused on small-scale relationships between bat echolocation and flight routes in laboratory and small-scale field experiments [5][6][7][8][9]. Recently, technological advances in the design of animal-borne devices have opened new avenues for research of bat navigation on a much larger spatial scale.…”