Entropy analysis of frequency and shape change in horseshoe bat biosonar.

Echolocating bats use ultrasonic pulses to collect information about their environments. Some of this information is encoded at the baffle structures-noseleaves (emission) and pinnae (reception)-that act as interfaces between the bats' biosonar systems and the external world. The baffle beam patterns encode the direction-dependent sensory information as a function of frequency and hence represent a view of the environment. To generate diverse views of the environment, the bats can vary beam patterns by changes to (1) the wavelengths of the pulses or (2) the baffle geometries. Here we compare the variability in sensory information encoded by just the use of frequency or baffle shape dynamics in horseshoe bats. For this, we use digital and physical prototypes of both noseleaf and pinnae. The beam patterns for all prototypes were either measured or numerically predicted. Entropy was used as a measure to compare variability as a measure of sensory information encoding capacity. It was found that new information was acquired as a result of shape dynamics. Furthermore, the overall variability available for information encoding was similar in the case of frequency or shape dynamics. Thus, shape dynamics allows the horseshoe bats to generate diverse views of the environment in the absence of broadband biosonar signals.

[1]  R. Rübsamen,et al.  Foraging behaviour and echolocation in the rufous horseshoe bat (Rhinolophus rouxi) of Sri Lanka , 2004, Behavioral Ecology and Sociobiology.

[2]  Uwe Firzlaff,et al.  Spectral directionality of the external ear of the lesser spear-nosed bat, Phyllostomus discolor , 2003, Hearing Research.

[3]  Rolf Müller,et al.  Sound-diffracting flap in the ear of a bat generates spatial information. , 2008, Physical review letters.

[4]  H. Schnitzler,et al.  Echolocation by Insect-Eating Bats , 2001 .

[5]  Luminita Göbbel,et al.  Morphology of the External Nose in Hipposideros diadema and Lavia frons with Comments on Its Diversity and Evolution among Leaf-Nosed Microchiroptera , 2001, Cells Tissues Organs.

[6]  Echolocation behavior of rufous horseshoe bats hunting for insects in the flycatcher-style , 2004, Journal of Comparative Physiology A.

[7]  Rolf Müller,et al.  Noseleaf Dynamics during Pulse Emission in Horseshoe Bats , 2012, PloS one.

[8]  H. Schneider,et al.  Die Ohrbewegungen der Hufeisenfledermäuse (Chiroptera, Rhinolophidae) und der Mechanismus des Bildhörens , 2004, Zeitschrift für vergleichende Physiologie.

[9]  H. Riquimaroux,et al.  Adaptive beam-width control of echolocation sounds by CF–FM bats, Rhinolophus ferrumequinum nippon, during prey-capture flight , 2013, Journal of Experimental Biology.

[10]  B. Siemers,et al.  Ground gleaning in horseshoe bats: comparative evidence from Rhinolophus blasii, R. euryale and R. mehelyi , 2004, Behavioral Ecology and Sociobiology.

[11]  Rolf Müller,et al.  Design of a dynamic sensor inspired by bat ears , 2012 .

[12]  H. Schnitzler,et al.  Echolocation signals of the greater horseshoe bat (Rhinolophus ferrumequinum) in transfer flight and during landing. , 1997, The Journal of the Acoustical Society of America.

[13]  Rolf Müller,et al.  Ear deformations give bats a physical mechanism for fast adaptation of ultrasonic beam patterns. , 2011, Physical review letters.

[14]  Rolf Müller,et al.  A comparison of the role of beamwidth in biological and engineered sonar , 2017, Bioinspiration & biomimetics.

[15]  Rolf Müller,et al.  Numerical analysis of biosonar beamforming mechanisms and strategies in bats. , 2010, The Journal of the Acoustical Society of America.

[16]  Andrew R. Webb,et al.  Statistical Pattern Recognition: Webb/Statistical Pattern Recognition , 2011 .

[17]  N Suga,et al.  Biosonar and neural computation in bats. , 1990, Scientific American.

[18]  Rolf Müller,et al.  Dynamic Substrate for the Physical Encoding of Sensory Information in Bat Biosonar. , 2017, Physical review letters.

[19]  M. C. Jones,et al.  On optimal data-based bandwidth selection in kernel density estimation , 1991 .

[20]  Rolf Müller,et al.  Interplay of lancet furrows and shape change in the horseshoe bat noseleaf. , 2015, The Journal of the Acoustical Society of America.

[21]  G. Arditi,et al.  Object localization using a biosonar beam: how opening your mouth improves localization , 2015, Royal Society Open Science.

[22]  Lasse Jakobsen,et al.  Convergent acoustic field of view in echolocating bats , 2012, Nature.

[23]  Jeremy M. V. Rayner,et al.  Foraging behavior and echolocation of wild horseshoe bats Rhinolophus ferrumequinum and R. hipposideros (Chiroptera, Rhinolophidae) , 1989, Behavioral Ecology and Sociobiology.

[24]  James A. Simmons,et al.  Lancet Dynamics in Greater Horseshoe Bats, Rhinolophus ferrumequinum , 2015, PloS one.

[25]  Lasse Jakobsen,et al.  Echolocating bats emit a highly directional sonar sound beam in the field , 2008, Proceedings of the Royal Society B: Biological Sciences.

[26]  G. K. Strother,et al.  Acoustical beam patterns for bats: some theoretical considerations. , 1970, The Journal of the Acoustical Society of America.

[27]  Ibrahim A. Ahmad,et al.  A nonparametric estimation of the entropy for absolutely continuous distributions (Corresp.) , 1976, IEEE Trans. Inf. Theory.

[28]  R L Jenison,et al.  A backpropagation network model of the monaural localization information available in the bat echolocation system. , 1997, The Journal of the Acoustical Society of America.

[29]  Rolf Müller,et al.  Interplay of static and dynamic features in biomimetic smart ears. , 2013, Bioinspiration & biomimetics.