Interpulse interval modulation by echolocating big brown bats (Eptesicus fuscus) in different densities of obstacle clutter

Petrites, Anthony E.; Eng, Oliver S.; Mowlds, Donald S.; Simmons, James A.; DeLong, Caroline M.

doi:10.1007/s00359-009-0435-6

Cited by 77 publications

(162 citation statements)

References 33 publications

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“…The obstacle array was made of black plastic chains (Fig. 1A) suspended vertically from the ceiling (12). Each chain was 2.4 m long (from ceiling to floor), with oval links 7 cm long and 4 cm wide, made from plastic rings 8 mm in diameter.…”

Section: Methodsmentioning

confidence: 99%

“…For initial training, chains were removed from successive rows in the center of the array to create a flight alley 75 cm wide. Bats received a mealworm after they landed on the far wall (12). After training, the chain array was rearranged to fill in the farther part of the alley so that during the experiments the bat flew into the enclosed space surrounded on three sides by hanging chains (Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Clutter interference is exacerbated by broadcast-echo ambiguity, creating a worst-case situation-self-generated clutter resulting from the use of too-short IPIs. The obvious effectiveness of echolocation in clutter (5,6,12,13) makes it desirable to learn how bats achieve this performance. When flying in dense clutter, big brown bats emit nearly all their sonar sounds in pairs, called "strobe groups," with shorter IPIs between members of the pairs set off by longer IPIs between one strobe group and the next (3,8,12,13).…”

mentioning

confidence: 99%

“…The obvious effectiveness of echolocation in clutter (5,6,12,13) makes it desirable to learn how bats achieve this performance. When flying in dense clutter, big brown bats emit nearly all their sonar sounds in pairs, called "strobe groups," with shorter IPIs between members of the pairs set off by longer IPIs between one strobe group and the next (3,8,12,13). The intervals between strobe groups usually are long enough to allow reception of all echoes (IPIs longer than ESDs), in effect setting a depth-of-field for echolocation (14), but the bat will experience broadcast-echo ambiguity if the shorter IPIs within strobe groups lead to overlap of echo streams from the more closely spaced broadcasts (IPIs shorter than ESDs).…”

mentioning

confidence: 99%

“…Here, we combine two recently introduced experimental methodsradio telemetry of sounds from the flying bat for very stable recording of the transmitted signals (15)(16)(17) in tandem with flight tests using an extended array of obstacles during which bats emit sounds at sufficiently short IPIs to create the conditions for ambiguity (12). The bat's response to ambiguity caused by overlap of extended echo streams is specific: Whenever ambiguity occurs (IPIs shorter than ESDs), the bat shifts the frequencies of the FM sweep upward in the first broadcast and downward in the second broadcast by several kilohertz (ΔF) in proportion to the degree of overlap (IPI minus ESD).…”

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confidence: 99%

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FM echolocating bats shift frequencies to avoid broadcast–echo ambiguity in clutter

Hiryu

Bates²,

Simmons

et al. 2010

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

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Sonar broadcasts are followed by echoes at different delays from objects at different distances. When broadcasts are emitted rapidly in cluttered surroundings, echo streams from successive broadcasts overlap and cause ambiguity in matching echoes to corresponding broadcasts. To identify reactions to ambiguity in clutter, echolocating bats that emit multiple-harmonic FM sounds were trained to fly into a dense, extended array of obstacles (multiple rows of vertically hanging chains) while the sonar sounds the bat emitted were recorded with a miniature radio microphone carried by the bat. Flight paths were reconstructed from thermal-infrared video recordings. Successive rows of chains extended more than 6 m in depth, so each broadcast was followed by a series of echoes from multiple rows of chains that lasted up to 40 ms. Bats emitted sounds in pairs ("strobe groups") at short (20-40 ms) interpulse intervals (IPIs) alternating with longer IPIs (>50 ms). For many short IPIs, the stream of echoes from the first broadcast was still arriving when the second broadcast was emitted. This overlap caused ambiguity about matching echoes with broadcasts. Bats shifted frequencies of the first sound in each strobe group upward and the second sound downward by 3-6 kHz. When overlap and ambiguity ceased, frequency shifts ceased also. Frequency differences were small compared with the total broadcast band, which was 75-80 kHz wide, but the harmonic structure of echoes enhances the differences in spectrograms. Bats could use time-frequency comparisons of echoes with broadcasts to assign echoes to the corresponding broadcasts and thus avoid ambiguity.bat sonar | clutter interference | echo delay | FM sounds

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

mentioning

confidence: 99%

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FM echolocating bats shift frequencies to avoid broadcast–echo ambiguity in clutter

Hiryu

Bates²,

Simmons

et al. 2010

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

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Do you hear what I see? Vocalization relative to visual detection rates of Hawaiian hoary bats (Lasiurus cinereus semotus)

Gorresen

Cryan

Montoya‐Aiona³

et al. 2017

Ecology and Evolution

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Bats vocalize during flight as part of the sensory modality called echolocation, but very little is known about whether flying bats consistently call. Occasional vocal silence during flight when bats approach prey or conspecifics has been documented for relatively few species and situations. Bats flying alone in clutter‐free airspace are not known to forgo vocalization, yet prior observations suggested possible silent behavior in certain, unexpected situations. Determining when, why, and where silent behavior occurs in bats will help evaluate major assumptions of a primary monitoring method for bats used in ecological research, management, and conservation. In this study, we recorded flight activity of Hawaiian hoary bats (Lasiurus cinereus semotus) under seminatural conditions using both thermal video cameras and acoustic detectors. Simultaneous video and audio recordings from 20 nights of observation at 10 sites were analyzed for correspondence between detection methods, with a focus on video observations in three distance categories for which accompanying vocalizations were detected. Comparison of video and audio detections revealed that a high proportion of Hawaiian hoary bats “seen” on video were not simultaneously “heard.” On average, only about one in three visual detections within a night had an accompanying call detection, but this varied greatly among nights. Bats flying on curved flight paths and individuals nearer the cameras were more likely to be detected by both methods. Feeding and social calls were detected, but no clear pattern emerged from the small number of observations involving closely interacting bats. These results may indicate that flying Hawaiian hoary bats often forgo echolocation, or do not always vocalize in a way that is detectable with common sampling and monitoring methods. Possible reasons for the low correspondence between visual and acoustic detections range from methodological to biological and include a number of biases associated with the propagation and detection of sound, cryptic foraging strategies, or conspecific presence. Silent flight behavior may be more prevalent in echolocating bats than previously appreciated, has profound implications for ecological research, and deserves further characterization and study.

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Localization and Classification of Targets by Echolocating Bats and Dolphins

Simmons

Houser

Kloepper

2014

Springer Handbook of Auditory Research

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Interpulse interval modulation by echolocating big brown bats (Eptesicus fuscus) in different densities of obstacle clutter

Cited by 77 publications

References 33 publications

FM echolocating bats shift frequencies to avoid broadcast–echo ambiguity in clutter

FM echolocating bats shift frequencies to avoid broadcast–echo ambiguity in clutter

Do you hear what I see? Vocalization relative to visual detection rates of Hawaiian hoary bats (Lasiurus cinereus semotus)

Localization and Classification of Targets by Echolocating Bats and Dolphins

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