Lin Yuan, Abaid Nicole, Müller Rolf
Department of Mechanical Engineering, Virginia Tech, 635 Prices Fork Road, Blacksburg, Virginia 24061, USA.
Department of Biomedical Engineering and Mechanics, Virginia Tech, 495 Old Turner Street, Blacksburg, Virginia 24061, USA.
J Acoust Soc Am. 2016 Dec;140(6):4318. doi: 10.1121/1.4971331.
Flying in swarms, e.g., when exiting a cave, could pose a problem to bats that use an active biosonar system because the animals could risk jamming each other's biosonar signals. Studies from current literature have found different results with regard to whether bats reduce or increase emission rate in the presence of jamming ultrasound. In the present work, the number of Eastern bent-wing bats (Miniopterus fuliginosus) that were flying inside a cave during emergence was estimated along with the number of signal pulses recorded. Over the range of average bat numbers present in the recording (0 to 14 bats), the average number of detected pulses per bat increased with the average number of bats. The result was interpreted as an indication that the Eastern bent-wing bats increased their emission rate and/or pulse amplitude with swarm size on average. This finding could be explained by the hypothesis that the bats might not suffer from substantial jamming probabilities under the observed density regimes, so jamming might not have been a limiting factor for their emissions. When jamming did occur, the bats could avoid it through changing the pulse amplitude and other pulse properties such as duration or frequency, which has been suggested by other studies. More importantly, the increased biosonar activities may have addressed a collision-avoidance challenge that was posed by the increased swarm size.
成群飞行，例如在离开洞穴时，对于使用主动生物声纳系统的蝙蝠来说可能会造成问题，因为这些动物可能会相互干扰彼此的生物声纳信号。现有文献的研究对于蝙蝠在存在干扰超声波的情况下是降低还是增加发射率得出了不同的结果。在本研究中，估计了东弯翅蝠（Miniopterus fuliginosus）在出洞时在洞穴内飞行的数量以及记录到的信号脉冲数量。在记录中出现的平均蝙蝠数量范围（0至14只蝙蝠）内，每只蝙蝠检测到的脉冲平均数量随蝙蝠平均数量的增加而增加。该结果被解释为表明东弯翅蝠平均随着群体规模的增加而提高了它们的发射率和/或脉冲幅度。这一发现可以用以下假设来解释：在观察到的密度条件下，蝙蝠可能不会遭受实质性的干扰概率，因此干扰可能不是它们发射的限制因素。当确实发生干扰时，蝙蝠可以通过改变脉冲幅度以及其他脉冲特性（如持续时间或频率）来避免干扰，其他研究也提出了这一点。更重要的是，生物声纳活动的增加可能应对了群体规模增加带来的避免碰撞挑战。
