Directionality of hearing in two CF/FM bats, Pteronotus parnellii and Rhinolophus rouxi

Firzlaff, Uwe; Schuller, Gerd

doi:10.1016/j.heares.2004.06.009

Cited by 32 publications

(48 citation statements)

References 51 publications

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“…The collection complied with the ethical guidelines and laws of the country. Both R. rouxi and P. discolor specimens were previously used in references [25, 29]. …”

Section: Methodsmentioning

confidence: 99%

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The Aerodynamic Cost of Head Morphology in Bats: Maybe Not as Bad as It Seems

et al. 2015

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At first sight, echolocating bats face a difficult trade-off. As flying animals, they would benefit from a streamlined geometric shape to reduce aerodynamic drag and increase flight efficiency. However, as echolocating animals, their pinnae generate the acoustic cues necessary for navigation and foraging. Moreover, species emitting sound through their nostrils often feature elaborate noseleaves that help in focussing the emitted echolocation pulses. Both pinnae and noseleaves reduce the streamlined character of a bat’s morphology. It is generally assumed that by compromising the streamlined charactered of the geometry, the head morphology generates substantial drag, thereby reducing flight efficiency. In contrast, it has also been suggested that the pinnae of bats generate lift forces counteracting the detrimental effect of the increased drag. However, very little data exist on the aerodynamic properties of bat pinnae and noseleaves. In this work, the aerodynamic forces generated by the heads of seven species of bats, including noseleaved bats, are measured by testing detailed 3D models in a wind tunnel. Models of Myotis daubentonii, Macrophyllum macrophyllum, Micronycteris microtis, Eptesicus fuscus, Rhinolophus formosae, Rhinolophus rouxi and Phyllostomus discolor are tested. The results confirm that non-streamlined facial morphologies yield considerable drag forces but also generate substantial lift. The net effect is a slight increase in the lift-to-drag ratio. Therefore, there is no evidence of high aerodynamic costs associated with the morphology of bat heads.

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“…The collection complied with the ethical guidelines and laws of the country. Both R. rouxi and P. discolor specimens were previously used in references [25, 29]. …”

Section: Methodsmentioning

confidence: 99%

“…These species feature the baroque noseleaves typical for this genus. The acoustic function of the pinnae of R. rouxi has been investigated by [4, 29], while the focussing effect of the noseleaves of this genus has been the topic of a number of studies [9, 10, 30]. E. fuscus is an aerial interceptor hunting for insect prey on the wing [31].…”

Section: Introductionmentioning

confidence: 99%

The Aerodynamic Cost of Head Morphology in Bats: Maybe Not as Bad as It Seems

et al. 2015

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“…1, bottom row) tend to have prominent side lobes that change direction in a frequency-dependent fashion. Previously published bat biosonar beam patterns of LDC [13][14][15][16] and HDC bats [17] support the existence of these differences. The beam patterns of HDC bats are well suited for on-axis target detection or identification but are not well adapted for estimating target direction based on spectral signatures.…”

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confidence: 64%

Ear Deformations Give Bats a Physical Mechanism for Fast Adaptation of Ultrasonic Beam Patterns

Gao

Balakrishnan

et al. 2011

Phys. Rev. Lett.

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A large number of mammals, including humans, have intricate outer ear shapes that diffract incoming sound in a direction-and frequency-specific manner. Through this physical process, the outer ear shapes encode sound-source information into the sensory signals from each ear. Our results show that horseshoe bats could dynamically control these diffraction processes through fast nonrigid ear deformations. The bats' ear shapes can alter between extreme configurations in about 100 ms and thereby change their acoustic properties in ways that would suit different acoustic sensing tasks.

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“…The CNS evaluates interaural differences in intensity (IID) and in time of arrival (ITD) that are indicative of the horizontal angle towards the echo-bearing object. By adding pinnae to their ears bats and other mammals generate direction-specific spectral filtering, which encodes the vertical bat-to-target angle (Grinnell and Grinnell, 1965;Fuzessery, 1996;Wotton et al, 1995;Firzlaff and Schuller, 2003;Firzlaff and Schuller, 2004;Aytekin et al, 2004). Echolocating bats time the delay between call and echo as an indicator of object distance (Griffin, 1958).…”

Section: Introductionmentioning

confidence: 99%

`Binaural echo disparity' as a potential indicator of object orientation and cue for object recognition in echolocating nectar-feeding bats

Holderied

Helversen

2006

Journal of Experimental Biology

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Echolocating bats emit ultrasonic calls through their mouth or their nostrils and receive echoes from objects with both their ears. Information conveyed in the echoes is the basis for their three-dimensional acoustic perception of the surroundings. The direction of an object is encoded in binaural echo differences, i.e. on the one hand in the different arrival times of its echo at the two ears, and on the other hand in spectral differences through directiondependent frequency filtering of head and pinnae. Insufficient attention has been paid, however, to the fact that three-dimensional objects produce structured spatial echo fields, and that the position of the ear in this field determines the echo it receives. We were interested to determine whether the two ears, in addition to directionspecific echo differences, receive object-specific echo disparities that might be useful for the bat. Our measurements with an artificial bat head, which consisted of two microphones and a small ultrasound loudspeaker arranged to resemble a bat's ears and mouth, revealed that echoes at the two ears differed largely depending on the shape and orientation of the echo-giving object. Binaural echo disparities of a bat-pollinated flower did indeed carry information about the orientation and, to a lesser extent, the shape of the flower. During flower approach such object-specific binaural echo disparities even exceed the binaural differences encoding direction of echo incidence, because the echo from the flower in front undergoes the same directional filtering by the two symmetrical ears. Nectar-feeding bats could use these object-specific binaural echo disparities not only to determine the object's orientation relative to the approaching bat, facilitating flight planning, but also to improve object recognition through spatial reconstruction of details of the object creating the echo. Our results suggest that the evaluation of binaural echo disparity has a greater importance for these tasks than has previously been assumed.

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Directionality of hearing in two CF/FM bats, Pteronotus parnellii and Rhinolophus rouxi

Cited by 32 publications

References 51 publications

The Aerodynamic Cost of Head Morphology in Bats: Maybe Not as Bad as It Seems

The Aerodynamic Cost of Head Morphology in Bats: Maybe Not as Bad as It Seems

Ear Deformations Give Bats a Physical Mechanism for Fast Adaptation of Ultrasonic Beam Patterns

`Binaural echo disparity' as a potential indicator of object orientation and cue for object recognition in echolocating nectar-feeding bats

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