Active Perception Lab, University Antwerp, Antwerp, Belgium.
PLoS Comput Biol. 2011 Dec;7(12):e1002268. doi: 10.1371/journal.pcbi.1002268. Epub 2011 Dec 1.
Rhinolophidae or Horseshoe bats emit long and narrowband calls. Fluttering insect prey generates echoes in which amplitude and frequency shifts are present, i.e. glints. These glints are reliable cues about the presence of prey and also encode certain properties of the prey. In this paper, we propose that these glints, i.e. the dominant glints, are also reliable signals upon which to base prey localization. In contrast to the spectral cues used by many other bats, the localization cues in Rhinolophidae are most likely provided by self-induced amplitude modulations generated by pinnae movement. Amplitude variations in the echo not introduced by the moving pinnae can be considered as noise interfering with the localization process. The amplitude of the dominant glints is very stable. Therefore, these parts of the echoes contain very little noise. However, using only the dominant glints potentially comes at a cost. Depending on the flutter rate of the insect, a limited number of dominant glints will be present in each echo giving the bat a limited number of sample points on which to base localization. We evaluate the feasibility of a strategy under which Rhinolophidae use only dominant glints. We use a computational model of the echolocation task faced by Rhinolophidae. Our model includes the spatial filtering of the echoes by the morphology of the sonar apparatus of Rhinolophus rouxii as well as the amplitude modulations introduced by pinnae movements. Using this model, we evaluate whether the dominant glints provide Rhinolophidae with enough information to perform localization. Our simulations show that Rhinolophidae can use dominant glints in the echoes as carriers for self-induced amplitude modulations serving as localization cues. In particular, it is shown that the reduction in noise achieved by using only the dominant glints outweighs the information loss that occurs by sampling the echo.
菊头蝠科或马蹄蝠发出长而窄带的叫声。飞舞的昆虫猎物会产生回声，其中存在幅度和频率的变化，即闪光。这些闪光是猎物存在的可靠线索，也编码了猎物的某些特性。在本文中，我们提出这些闪光，即主要闪光，也是基于猎物定位的可靠信号。与许多其他蝙蝠使用的光谱线索不同，菊头蝠科的定位线索很可能是由耳郭运动产生的自诱导幅度调制提供的。耳郭运动不引入回声中的幅度变化可以被认为是干扰定位过程的噪声。回声中的主要闪光幅度非常稳定。因此，这些回声部分包含的噪声非常少。然而，只使用主要闪光可能会付出代价。根据昆虫的扑动率，每个回声中只会出现有限数量的主要闪光，这使得蝙蝠在定位时只有有限数量的样本点。我们评估了菊头蝠科仅使用主要闪光的策略的可行性。我们使用了一种针对菊头蝠科回声定位任务的计算模型。我们的模型包括了 Rhinolophus rouxii 声纳设备形态对回声的空间滤波以及耳郭运动引入的幅度调制。使用这个模型，我们评估了主要闪光是否为菊头蝠科提供了足够的定位信息。我们的模拟表明，菊头蝠科可以使用回声中的主要闪光作为自诱导幅度调制的载体，作为定位线索。特别是，结果表明，仅使用主要闪光所获得的噪声减少量超过了由于采样回声而导致的信息损失。
