Hase Kazuma, Miyamoto Takara, Kobayasi Kohta I, Hiryu Shizuko
Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe 610-0321, Japan.
Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe 610-0321, Japan; JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
Behav Processes. 2016 Jul;128:126-33. doi: 10.1016/j.beproc.2016.04.017. Epub 2016 May 6.
In the presence of multiple flying conspecifics, echolocating bats avoid jamming by adjusting the spectral and/or temporal features of their vocalizations. However, little is known about how bats alter their pulse acoustic characteristics to adapt to an acoustically jamming situation during flight. We investigated echolocation behavior in a bat (Miniopterus fuliginosus) during free flight under acoustic jamming conditions created by downward FM jamming sounds mimicking bat echolocation sounds. In an experimental chamber, the flying bat was exposed to FM jamming sounds with different terminal frequencies (TFs) from loudspeakers. Echolocation pulses emitted by the flying bat were recorded using a telemetry microphone (Telemike) mounted on the back of the bat. The bats immediately (within 150ms) shifted the TFs of emitted pulses upward when FM jamming sounds were presented. Moreover, the amount of upward TF shift differed depending on the TF ranges of the jamming sounds presented. When the TF range was lower than or overlapped the bat's mean TF, the bat TF shifted significantly upward (by 1-2kHz, Student's t-test, P<0.05), corresponding to 3-5% of the total bandwidth of their emitted pulses. These findings indicate that bats actively avoid overlap of the narrow frequency band around the TF.
在存在多个同种飞行个体的情况下，回声定位蝙蝠通过调整其发声的频谱和/或时间特征来避免干扰。然而，关于蝙蝠在飞行过程中如何改变其脉冲声学特征以适应声学干扰情况，我们知之甚少。我们研究了一种蝙蝠（黑腹鼠耳蝠）在由模仿蝙蝠回声定位声音的向下调频干扰声所营造的声学干扰条件下自由飞行时的回声定位行为。在一个实验室内，飞行中的蝙蝠被来自扬声器的具有不同终端频率（TF）的调频干扰声所干扰。使用安装在蝙蝠背部的遥测麦克风（Telemike）记录飞行蝙蝠发出的回声定位脉冲。当呈现调频干扰声时，蝙蝠会立即（在150毫秒内）将发出脉冲的终端频率向上移动。此外，终端频率向上移动的幅度因所呈现干扰声的终端频率范围而异。当终端频率范围低于或与蝙蝠的平均终端频率重叠时，蝙蝠的终端频率会显著向上移动（移动1 - 2千赫，学生t检验，P < 0.05），这相当于其发出脉冲总带宽的3 - 5%。这些发现表明，蝙蝠会主动避免终端频率周围窄频带的重叠。
