Adaptive echolocation sounds of insectivorous bats, <i>Pipistrellus abramus</i>, during foraging flights in the field

Hiryu, Shizuko; Hagino, Tomotaka; Fujioka, Emyo; Riquimaroux, Hiroshi; Watanabe, Yoshiaki

doi:10.1121/1.2947629

Cited by 29 publications

(26 citation statements)

References 13 publications

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“…The Japanese pipistrelle bat (Pipistrellus abramus) increased its body weight by up to ∼20% during nightly foraging (20). We previously reported that P. abramus are capable of capturing prey every 2-3 s (15,21). In this study, we have shown that the bats select flight paths to efficiently capture consecutive prey items.…”

Section: Discussionmentioning

confidence: 78%

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Echolocating bats use future-target information for optimal foraging

Fujioka

Aihara

Sumiya

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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When seeing or listening to an object, we aim our attention toward it. While capturing prey, many animal species focus their visual or acoustic attention toward the prey. However, for multiple prey items, the direction and timing of attention for effective foraging remain unknown. In this study, we adopted both experimental and mathematical methodology with microphone-array measurements and mathematical modeling analysis to quantify the attention of echolocating bats that were repeatedly capturing airborne insects in the field. Here we show that bats select rational flight paths to consecutively capture multiple prey items. Microphone-array measurements showed that bats direct their sonar attention not only to the immediate prey but also to the next prey. In addition, we found that a bat's attention in terms of its flight also aims toward the next prey even when approaching the immediate prey. Numerical simulations revealed a possibility that bats shift their flight attention to control suitable flight paths for consecutive capture. When a bat only aims its flight attention toward its immediate prey, it rarely succeeds in capturing the next prey. These findings indicate that bats gain increased benefit by distributing their attention among multiple targets and planning the future flight path based on additional information of the next prey. These experimental and mathematical studies allowed us to observe the process of decision making by bats during their natural flight dynamics.bat sonar | aerial capture | microphone array | mathematical modeling | flight dynamics S electively focusing attention on a particular target allows us to effectively extract information (1-4). Animals spatially focus their attention toward prey for suitable foraging (5, 6). During prey pursuit, most animals direct their visual attention toward it [e.g., tiger beetle (7), dragonfly (8), and falcon (9)]. Specifically, for example, dragonflies maintain a prey item at a constant retinal position during approaching it so that they steer an interception flight path (interception strategy) (10). However, for multiple prey items, the direction and timing of attention for effective foraging remain unknown.Echolocating bats actively emit sonar signals to obtain surrounding information and adaptively change the characteristics of the emissions depending on the situation (11). Therefore, their attention in terms of the sonar (sonar attention) is characterized as the direction to which bats emit their sonar beams (12-14). When echolocating bats approach an airborne insect, the sonar attention directs toward the prey (12, 13). During natural foraging, the sonar attention of bats alternately shifts from their flying direction to the side (15). Additionally the wild bats are capable of capturing two prey items within the short interval of 1 s (16).We predicted that bats localize multiple prey items by distributing their attention between them and then select an efficient flight path to successively capture the multiple prey. To test this prediction, ...

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Section: Discussionmentioning

confidence: 78%

“…However, in fact, predators usually capture successive prey items (e.g., aerial-feeding bats) (21). For multiple targets, it is beneficial for bats in the wild to distribute their sonar attention and flight attention among multiple targets and to plan the future flight path based on the next prey for effective foraging.…”

Section: Discussionmentioning

confidence: 99%

Echolocating bats use future-target information for optimal foraging

Fujioka

Aihara

Sumiya

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…During the search phase of foraging by echolocation in the field, pipistrellus bats and Epitesicus fuscus lengthen the duration of the TF portion of the downward FM pulse, which creates a quasi-CF sound [e.g., Pipistrellus abramus (Hiryu et al, 2008), Epitesicus fuscus (Surlykke and Moss, 2000)]. The long, narrowband FM pulses are suited for detecting frequency modulations in echoes from fluttering insects, and for reducing the transmission loss of sounds in air due to energy concentration in a narrow frequency range.…”

Section: Discussionmentioning

confidence: 99%

“…Pipistrelle bats are known to use flexible frequency-modulated (FM) pulses; they emit narrowband FM a) Author to whom correspondence should be addressed. pulses with long duration (Quasi-CF, >10 ms) by expanding the terminal frequency portion of the downward FM sweep of the fundamental component (terminal frequency; TF) (Hiryu et al, 2008). There are no developmental data on vocalizations and echolocation by infant P. abramus.…”

Section: Introductionmentioning

confidence: 99%

Developmental changes in ultrasonic vocalizations by infant Japanese echolocating bats, Pipistrellus abramus

Hiryu

Riquimaroux

2011

The Journal of the Acoustical Society of America

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Developmental changes in vocalizations by Pipistrellus abramus were investigated during the first post-natal month. Vocalizations by pups on the day of birth were frequency-modulated ultrasounds from 30.0 ± 4.0 kHz to 19.3 ± 1.9 kHz with multiple harmonics. The terminal frequency of the second harmonic (TF2) of pup vocalizations corresponded to that of the fundamental (TF1) in adult bats (41.4 ± 2.6 kHz), suggesting that pup vocalizations can be easily detected by the mother. In addition, there are two types of infant vocalization: short duration echolocation precursor and long duration isolation calls, which showed separate developmental patterns over time.

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“…In addition, behavioral experiments have shown that Pteronotus parnellii ͑a CF-FM bat͒ discriminates at least a 50-Hz frequency difference in 60 kHz between CF 2 echoes ͑Riquima-roux et al., 1991, 1992͒. These findings indicate that the CF component may be effective in the detection of small frequency modulations in echoes caused by fluttering prey. Interestingly, during foraging in the field, some FM bat species lengthen the duration of the end frequency portion of the downward FM sweep of the fundamental frequency component ͑terminal frequency; TF͒, which creates a sound similar to a CF sound ͑e.g., Pipistrellus bats, Schnitzler et al, 1987;Kalko, 1995;Hiryu et al, 2008; Epitesicus fuscus, Surlykke and Moss, 2000͒. Because the long, narrowband FM pulses are suited for detecting frequency modulation in echo from fluttering insects, these FM bat species vary the frequency structure of the pulse from a quasi-CF, to search for targets, to a wideband FM pulse, for precise target ranging during the approach phase of echolocation ͑Simmons et al, 1979͒. The inferior colliculus ͑IC͒ is an important relay nucleus in both the afferent and the efferent auditory pathways, with well-studied specializations for processing echoes.…”

Section: Introductionmentioning

confidence: 99%

Frequency tuning and latency organization of responses in the inferior colliculus of Japanese house bat, Pipistrellus abramus

Goto

Hiryu

Riquimaroux

2010

The Journal of the Acoustical Society of America

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Pipistrellus abramus emits quasi-constant frequency pulses during search, which extend the end frequency portion of the downward frequency-modulated sweep (terminal frequency; TF). If the narrowed frequency range is important for detecting a small frequency change caused by insect fluttering, the bats may need much finer frequency resolution at the TF. To test this hypothesis, the distribution of the best frequencies (BFs) in the inferior colliculus (IC) was electrophysiologically measured. The TF of the echolocation pulse was 41.44+/-2.62 kHz. The frequency range of 35-45 kHz was overrepresented in the IC (n=50/105; 48%), and a faint second peak was seen at 75-85 kHz (the second harmonic of the TF) in the BF distribution. The BF increased as a function of recording depth along the dorsoventral axis, except for the BFs of 35-45 and 75-85 kHz, which were found at a wide range of depths. The response latency ranged between 3.7 and 23.2 ms for the BFs of 35-45 kHz, and the maximum target range was estimated to be 3.3 m from the delay line observed in the IC. These electrophysiological measures suggest the importance of a target distance within approximately 3 m, which is consistent with behavioral measures during foraging in this species.

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Adaptive echolocation sounds of insectivorous bats, Pipistrellus abramus, during foraging flights in the field

Cited by 29 publications

References 13 publications

Echolocating bats use future-target information for optimal foraging

Echolocating bats use future-target information for optimal foraging

Developmental changes in ultrasonic vocalizations by infant Japanese echolocating bats, Pipistrellus abramus

Frequency tuning and latency organization of responses in the inferior colliculus of Japanese house bat, Pipistrellus abramus

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