Stabilization of perceived echo amplitudes in echolocating bats. I. Echo detection and automatic gain control in the big brown bat, E
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Hartley, David J.

doi:10.1121/1.402639

Cited by 66 publications

(49 citation statements)

References 27 publications

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“…Bats reduce call duration to avoid pulse-echo overlap with nearby objects (Cahlander et al, 1964;Kalko and Schnitzler, 1989;Schnitzler et al, 1987), widen call bandwidth to better localize objects (Faure and Barclay, 1994;Hartley, 1992;Kalko and Schnitzler, 1993;Surlykke et al, 1993), reduce call intensity as they approach objects as a method for keeping target echo strength constant (Hartley, 1992;Hiryu et al, 2007), and decrease directionality to widen the field of view as they attack prey (Jakobsen and Surlykke, 2010). These adaptations occur as the bat adjusts the timing of sonar sounds, and may also be influenced by the temporal dynamics of respiration and flight kinematics.…”

Section: Introductionmentioning

confidence: 99%

Tight coordination of aerial flight maneuvers and sonar call production in insectivorous bats

Falk

Kasnadi

Moss

2015

Journal of Experimental Biology

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Echolocating bats face the challenge of coordinating flight kinematics with the production of echolocation signals used to guide navigation. Previous studies of bat flight have focused on kinematics of fruit and nectar-feeding bats, often in wind tunnels with limited maneuvering, and without analysis of echolocation behavior. In this study, we engaged insectivorous big brown bats in a task requiring simultaneous turning and climbing flight, and used synchronized high-speed motion-tracking cameras and audio recordings to quantify the animals' coordination of wing kinematics and echolocation. Bats varied flight speed, turn rate, climb rate and wingbeat rate as they navigated around obstacles, and they adapted their sonar signals in patterning, duration and frequency in relation to the timing of flight maneuvers. We found that bats timed the emission of sonar calls with the upstroke phase of the wingbeat cycle in straight flight, and that this relationship changed when bats turned to navigate obstacles. We also characterized the unsteadiness of climbing and turning flight, as well as the relationship between speed and kinematic parameters. Adaptations in the bats' echolocation call frequency suggest changes in beam width and sonar field of view in relation to obstacles and flight behavior. By characterizing flight and sonar behaviors in an insectivorous bat species, we find evidence of exquisitely tight coordination of sensory and motor systems for obstacle navigation and insect capture.

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Section: Introductionmentioning

confidence: 99%

Tight coordination of aerial flight maneuvers and sonar call production in insectivorous bats

Falk

Kasnadi

Moss

2015

Journal of Experimental Biology

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“…Bats modify echolocation call parameters such as duration, repetition rate, and intensity in response to obstacles and habitat (9,10). In general, aerial insectivorous bats increase bandwidth and repetition rate and decrease duration of their calls as they close in on prey during a pursuit sequence (11).…”

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confidence: 99%

“…We filtered the recordings using third-octave band-pass filters centered on the approximate peak frequency of the approach call for each species and of the low component of the terminal phase calls, i.e., 55 kHz and 27.5 kHz for M. daubentonii and 35 kHz and 17.5 kHz for E. serotinus. The rms pressure of each recorded signal was calculated for each third-octave band-pass filter and the rms pressures were compensated for spherical spreading loss [20×log 10 (distance/10 cm)], atmospheric attenuation (40) and angle of incidence on the microphones (41).…”

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confidence: 99%

Vespertilionid bats control the width of their biosonar sound beam dynamically during prey pursuit

Jakobsen

Surlykke

2010

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

123

149

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Animals using sound for communication emit directional signals, focusing most acoustic energy in one direction. Echolocating bats are listening for soft echoes from insects. Therefore, a directional biosonar sound beam greatly increases detection probability in the forward direction and decreases off-axis echoes. However, high directionality has context-specific disadvantages: at close range the detection space will be vastly reduced, making a broad beam favorable. Hence, a flexible system would be very advantageous. We investigated whether bats can dynamically change directionality of their biosonar during aerial pursuit of insects. We trained five Myotis daubentonii and one Eptesicus serotinus to capture tethered mealworms and recorded their echolocation signals with a multimicrophone array. The results show that the bats broaden the echolocation beam drastically in the terminal phase of prey pursuit. M. daubentonii increased the half-amplitude angle from approximately 40°to approximately 90°horizontally and from approximately 45°to more than 90°vertically. The increase in beam width is achieved by lowering the frequency by roughly one octave from approximately 55 kHz to approximately 27.5 kHz. The E. serotinus showed beam broadening remarkably similar to that of M. daubentonii. Our results demonstrate dynamic control of beam width in both species. Hence, we propose directionality as an explanation for the frequency decrease observed in the buzz of aerial hawking vespertilionid bats. We predict that future studies will reveal dynamic control of beam width in a broad range of acoustically communicating animals.A coustic communication plays a major role for conspecific and predator/prey interactions in many animals. Features of emitted sounds, such as time-frequency structure, intensity, and directionality, are central for communication range and direction. Flexibility in acoustic behavior allows for adaptive changes in sound signals to the constraints of a variety of contexts and purposes (1, 2). Directionality defines the angle of attention and is consequently a spatial filter for communication. Thus, directionality is as significant as other acoustic features, but as a result of the methodological challenge in measuring it, directionality has only very rarely been studied in the field (3-6), and almost nothing is known about possible dynamic changes in directionality in response to behavioral tasks. Bats are ideal animals in which to study dynamic changes in directionality, as recording their highintensity echolocation calls allow us to infer, from the bat's adaptive vocal changes to the changing context, which acoustic elements are important for perception through sound.Echolocating bats can hunt and navigate without light, emitting short high-frequency sound pulses to determine the direction, distance, and features of objects in the environment from binaural cues, arrival time, amplitude, and spectrum of sonar reflections (7,8). Bats modify echolocation call parameters such as duration, repetition rate, and...

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“…While previous studies have indicated that many bats vary their signal amplitude to compensate for range-dependent transmission loss and maintain prey echoes at relatively constant levels (Hartley, 1992a;Surlykke and Kalko, 2008), similar transmit-side automatic gain control to compensate for variations in prey target strength has not previously been observed (but see Au, 1993 for a brief discussion of the topic for dolphins). In fact, Boonman and Jones (2002) found that while Daubenton's bats (Myotis daubentonli) varied their click intensity with target range, their signal amplitude increased by only about 4 dB when target strength was reduced by about 17-18 dB.…”

Section: Comparison Of Various Conditionsmentioning

confidence: 99%

“…In conjunction with this transmit-side AGC, some bats employ receiver-side AGC, reducing their middle-ear sensitivity by about 4-7 dB per halving of target range (Kick and Simmons, 1984;Hartley, 1992a;Boonman and Jones, 2002). Together, transmit-and receiver-side AGC can maintain constant echo intensity at the level of the cochlea despite changes in bat-target range, which may simplify the bats' echo-processing task.…”

Section: Click Levelsmentioning

confidence: 99%

Echolocation-based foraging by harbor porpoises and sperm whales, including effects of noise and acoustic propagation

DeRuiter¹

2008

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In this thesis, I provide quantitative descriptions of toothed whale echolocation and foraging behavior, including assessment of the effects of noise on foraging behavior and the potential influence of ocean acoustic propagation conditions on biosonar detection ranges and whale noise exposure. In addition to presenting some novel basic science findings, the case studies presented in this thesis have implications for future work and for management.In Chapter 2, I describe the application of a modified version of the Dtag to studies of harbor porpoise echolocation behavior. The study results indicate how porpoises vary the rate and level of their echolocation clicks during prey capture events; detail the differences in echolocation behavior between different animals and in response to differences in prey fish; and show that, unlike bats, porpoises continue their echolocation buzz after the moment of prey capture.Chapters 3-4 provide case studies that emphasize the importance of applying realistic models of ocean acoustic propagation in marine mammal studies. These chapters illustrate that, although using geometric spreading approximations to predict communication/target detection ranges or noise exposure levels is appropriate in some cases, it can result in large errors in other cases, particularly in situations where refraction in the water column or multi-path acoustic propagation are significant.Finally, in Chapter 5, I describe two methods for statistical analysis of whale behavior data, the rotation test and a semi-Markov chain model. I apply those methods to test for changes in sperm whale foraging behavior in response to airgun noise exposure. Test results indicate that, despite the low-level exposures experienced by the whales in the study, some (but not all) of them reduced their buzz production rates and altered other foraging behavior parameters in response to the airgun exposure. Sincere thanks also to the many other people who have helped with data collection and analysis over the course of my graduate work, and also to everyone who offered comments on drafts of this thesis. More detailed acknowledgments can be found at the end of each chapter, but here I would especially like to thank the following. Thesis Objectives and Chapter 1 OverviewThe goal of my thesis research has been to provide quantitative descriptions of toothed whale echolocation and foraging behavior (Chapters 2 and 5), including assessment of the effects of noise on foraging behavior (Chapter 5) and the potential influence of ocean acoustic propagation conditions on biosonar detection ranges (Chapter 3) and whale noise exposure (Chapter 4). I have focused on two study species, the harbor porpoise (Phocoena phocoena, Chapters 2-3) and the sperm whale (Physeter macrocephalus, Chapters 4-5).The following sections present background information relevant to the research presented in the rest of the thesis, beginning with a review of previous research on the use of echolocation by foraging animals. This review is followed by b...

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Stabilization of perceived echo amplitudes in echolocating bats. I. Echo detection and automatic gain control in the big brown bat, E p t e s i c u s f u s c u s, and the f

Cited by 66 publications

References 27 publications

Tight coordination of aerial flight maneuvers and sonar call production in insectivorous bats

Tight coordination of aerial flight maneuvers and sonar call production in insectivorous bats

Vespertilionid bats control the width of their biosonar sound beam dynamically during prey pursuit

Echolocation-based foraging by harbor porpoises and sperm whales, including effects of noise and acoustic propagation

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