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Echo-intensity compensation in echolocating bats (Pipistrellus abramus) during flight measured by a telemetry microphone
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Image of FIG. 1.
FIG. 1.

Japanese house bat (P. abramus) with an onboard microphone (Telemike) mounted on its back. The Telemike consists of a 1/8-inch condenser microphone, FM transmitter, battery, and transmitting wire antenna (weight: , including the battery).

Image of FIG. 2.
FIG. 2.

Pulse-echo pairs recorded with the Telemike while a bat approached the target wall. (A) Sonograms at a target distance of (top) and (bottom). Arrows indicate the echoes returning from the target wall (see text). (B) Changes in echo delay determined from sound data as a function of target distance during the landing flight for two bats (solid circles). Circle size indicates relative variation in echo intensity where bigger circles designate sounds of greater intensity relative to smaller circles. The three lines represent echo delays between the flying bat and three targets—the target wall, floor, and ceiling of the chamber—calculated using three-dimensional coordinate data of the bat.

Image of FIG. 3.
FIG. 3.

Typical echolocation pulse emitted by P. abramus during the landing flight, recorded by the Telemike. Data were taken from sound recorded at a distance of from the target wall. Echolocation pulses usually contained several harmonics, with the first being dominant.

Image of FIG. 4.
FIG. 4.

Three-dimensional spatiotemporal reconstructions of echolocation behavior during landing flights for three bats. Coordinate grids show the dimensions of the flight chamber . Echolocation pulses recorded by the Telemike are placed alongside the flight trajectory. The arrow indicates the flight direction of the bat. The amplitude of emitted pulses decreased as the bat approached the target wall.

Image of FIG. 5.
FIG. 5.

Changes in intensity in the peak energy portion (the sonogram exhibited a peak in energy at about during flight, which was approximately higher than the terminal frequency) of the pulse-echo pairs, normalized to the average of intensity of the pulse emitted during the search phase. (A) Sound intensity of the pulse (solid circles) and echo (open circles) as a function of target distance for three bats. Data were taken from three flight sessions of each of three bats. (B) Decrease in pulse intensity for a total of nine flights of three bats. The solid line indicates the correlation line. Pulse intensity decreased by on halving the target distance ( decrease per decade of the target distance). (C) Distribution of observed echo intensity (relative to the average of the pulse intensity during the search phase) during the landing approach for nine flight sessions of three bats.

Image of FIG. 6.
FIG. 6.

Sound intensity of pulse-echo pairs as a function of target distance for one flight session by Bat A. Asterisks indicate echoes from the target wall, determined from sound and three-dimensional coordinate data (see Methods). The intensity of the echo returning from the target wall indicates a nearly constant intensity, while the bat considerably decreased the pulse intensity as it approached the target wall.

Image of FIG. 7.
FIG. 7.

Three-dimensional spatiotemporal reconstruction for a U-turn flight (A), and sound intensity of the pulse (solid circles) and echo (open circles) as a function of the distance to the wall with a landing mesh (referred to as “target wall” in case of the landing flight) while a bat making U-turn (B). Asterisk indicates the echo from that wall. The bat made a U-turn at a distance of (marked U) from that wall. The bat during the U-turn did not decrease the intensity of emitted pulses as approached that wall, as seen when they were landing.


Generic image for table

Signal characteristics of the echolocation pulse from P. abramus at rest. iFM: initial FM; tFM: terminal FM; BW: bandwidth.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Echo-intensity compensation in echolocating bats (Pipistrellus abramus) during flight measured by a telemetry microphone