1月25日,一项在线发表于英国皇家学会《界面》杂志的最新研究,描述了位于蹄鼻蝠(菊头蝠科)主鼻叶上方的皱折是如何帮助它们集中声束并且减少环境中杂音干扰的。
蹄鼻蝠的鼻子又宽又扁,虽然看起来可能不是那么漂亮,却能在蹄鼻蝠飞行和觅食时帮上大忙。
蹄鼻蝠的鼻子虽然看起来很丑,却能帮助它们飞行和觅食。
蝙蝠利用回声定位,即通过发出高声调的声音并对反射回来的回声进行分析来实现移动和猎食。
研究人员制作了一只蹄鼻蝠的头部模型和不同的五官模型来探寻这些皱折是如何影响声音传递的。
他们发现,当蝙蝠通过鼻子发出声音时,这些皱折能够减小主鼻叶的尺寸,由此使声束的聚焦变紧。虽然这种方式降低了蝙蝠定位猎物的能力,但同时也减少了栖息地中,如森林里的杂音的干扰。
这个发现和之前的研究相矛盾。此前,研究人员认为这些皱折使蝙蝠的声束变宽,并且可能会帮助它们探知自己离地面有多高。而这项最新研究的作者们认为,之前研究人员在错误的范围内探测到了回声频率改变,所以才会有如此推论。(生物谷 Bioon.com)
doi:10.1098/rsif.2011.0812
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The furrows of Rhinolophidae revisited
Dieter Vanderelst, Reijniers Jonas and Peremans Herbert
Rhinolophidae, a family of echolocating bats, feature very baroque noseleaves that are assumed to shape their emission beam. Zhuang & Muller (Zhuang & Muller 2006 Phys. Rev. Lett. 97, 218701 (doi:10.1103/PhysRevLett.97.218701); Zhuang & Muller 2007 Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 76(Pt. 1), 051902 (doi:10.1103/PhysRevE.76.051902)) have proposed, based on finite element simulations, that the furrows present in the noseleaves of these bats act as resonance cavities. Using Rhinolophus rouxi as a model species, they reported that a resonance phenomenon causes the main beam to be elongated at a particular narrow frequency range. Virtually filling the furrows reduced the extent of the main lobe. However, the results of Zhuang & Muller are difficult to reconcile with the ecological background of R. rouxi. In this report, we replicate the study of Zhuang & Muller, and extend it in important ways: (i) we take the filtering of the moving pinnae into account, (ii) we use a model of the echolocation task faced by Rhinolophidae to estimate the effect of any alterations to the emission beam on the echolocation performance of the bat, and (iii) we validate our simulations using a physical mock-up of the morphology of R. rouxi. In contrast to Zhuang & Muller, we find the furrows to focus the emitted energy across the whole range of frequencies contained in the calls of R. rouxi (both in simulations and in measurements). Depending on the frequency, the focusing effect of the furrows has different consequences for the estimated echolocation performance. We argue that the furrows act to focus the beam in order to reduce the influence of clutter echoes.