Auditory Relationships to Size in Noctuid Moths: Bigger Is Better

Surlykke, Annemarie; Filskov, Mads; Fullard, James H.; Forrest, Evelyn

doi:10.1007/s001140050607

Cited by 80 publications

(88 citation statements)

References 11 publications

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“…Thus, the quietness of courtship songs would be crucial to avoid eavesdropping by neighboring males. Also predatory bats would not be able to detect Ostrinia songs from a distance Ͼ20 cm, assuming bats' auditory threshold to be 20 dB SPL (21). Our discovery of extremely low-intensity ultrasonic communication may point to a whole undiscovered world of private communication using quiet ultrasound.…”

Section: Resultsmentioning

confidence: 89%

Moths produce extremely quiet ultrasonic courtship songs by rubbing specialized scales

Nakano

Skals²,

Takanashi³

et al. 2008

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

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Insects have evolved a marked diversity of mechanisms to produce loud conspicuous sounds for efficient communication. However, the risk of eavesdropping by competitors and predators is high. Here, we describe a mechanism for producing extremely lowintensity ultrasonic songs (46 dB sound pressure level at 1 cm) adapted for private sexual communication in the Asian corn borer moth, Ostrinia furnacalis. During courtship, the male rubs specialized scales on the wing against those on the thorax to produce the songs, with the wing membrane underlying the scales possibly acting as a sound resonator. The male's song suppresses the escape behavior of the female, thereby increasing his mating success. Our discovery of extremely low-intensity ultrasonic communication may point to a whole undiscovered world of private communication, using ''quiet'' ultrasound.acoustic communication ͉ hearing ͉ playback experiment ͉ receiver bias ͉ sound-producing organ

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Section: Resultsmentioning

confidence: 89%

Moths produce extremely quiet ultrasonic courtship songs by rubbing specialized scales

Nakano

Skals²,

Takanashi³

et al. 2008

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

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“…Again assuming that part of the array (one microphone) resembles a point target with a target strength close to a medium-sized moth of -20dB (re.0.1m) (Surlykke et al, 1999) and using an atmospheric attenuation of 1.2dBm -1 at 40kHz (15°C), then the echo level at 1m target distance would be ca. 23dB at the bat's ear, which is probably above but close to the bat's hearing threshold, whereas the echo level from a similar sized clutter object 2m behind the microphone would be approximately -1dB, and hence below the threshold for hearing under noisy conditions as in flight.…”

Section: Source Level and Received Echo Levelmentioning

confidence: 99%

New model for gain control of signal intensity to object distance in echolocating bats

Nørum

Brinkløv

Surlykke

2012

Journal of Experimental Biology

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SUMMARYEcholocating bats emit ultrasonic calls and listen for the returning echoes to orient and localize prey in darkness. The emitted source level, SL (estimated signal intensity 10cm from the mouth), is adjusted dynamically from call to call in response to sensory feedback as bats approach objects. A logarithmic relationship of SL20log 10 (x), i.e. 6dB output reduction per halving of distance, x, has been proposed as a model for the relationship between emitted intensity and object distance, not only for bats but also for echolocating toothed whales. This logarithmic model suggests that the approaching echolocator maintains a constant intensity impinging upon the object, but it also implies ever-increasing source levels with distance, a physical and biological impossibility. We developed a new model for intensity compensation with an exponential rise to the maximum source level: SLSL max -ae -bx . In addition to providing a method for estimating maximum output, the new model also offers a tool for estimating a minimum detection distance where intensity compensation starts. We tested the new exponential model against the ʻconventionalʼ logarithmic model on data from five bat species. The new model performed better in 77% of the trials and as good as the conventional model in the rest (23%). We found much steeper rates of compensation when fitting the model to individual rather than pooled data, with slopes often steeper than -20dB per halving of distance. This emphasizes the importance of analyzing individual events. The results are discussed in light of habitat constraints and the interaction between bats and their eared prey.

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“…4) from the emitted intensities, the directional patterns, an assumed detection threshold of 20 dB for the bat, and a target-strength for the prey of −40 dB at 10 cm (42).…”

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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.

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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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Auditory Relationships to Size in Noctuid Moths: Bigger Is Better

Cited by 80 publications

References 11 publications

Moths produce extremely quiet ultrasonic courtship songs by rubbing specialized scales

Moths produce extremely quiet ultrasonic courtship songs by rubbing specialized scales

New model for gain control of signal intensity to object distance in echolocating bats

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

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