The sound emission pattern and the acoustical role of the noseleaf in the echolocating bat, C a r o l l i a p e r s p i c i l<

Abstract

Carollia perspicillata (Phyllostomidae) is a frugivorous bat that emits low-intensity, broadband, frequency-modulated echolocation pulses through nostrils surrounded by a noseleaf. The emission pattern of this bat is of interest because the ratio between the nostril spacing and the emitted wavelength varies during the pulse, causing complex interference patterns in the horizontal dimension. Sound pressures around the bat were measured using a movable microphone and were referenced to those at a stationary microphone positioned directly in front of the animal. Interference between the nostrils was confirmed by blocking one nostril, which eliminated sidelobes and minima in the emission pattern, and by comparison of real emission patterns with simple computer models. The positions of minima in the patterns indicate effective nostril spacings of over a half-wavelength. Displacement of the dorsal lancet of the noseleaf demonstrated that this structure directs sound in the vertical dimension.

Phylogeny of Phyllostomid Bats (Mammalia: Chiroptera): Data From Diverse Morphological Systems, Sex Chromosomes, and Restriction Sites

“…These authors found that the spear acts to direct echolocation pulses in the vertical dimension, but does not affect emission in the horizontal dimension. Interference between the emission from each nostril is apparently used to direct sound in the horizontal dimension (Hartley and Suthers, 1987). These results are similar to those for other species of bats in which the role of the noseleaf was studied (e.g., Megaderma and Rhinolophus; Möhres and Neuwiler, 1966;Strother and Mogus, 1970;Sokolov and Makarov, 1971;Schnitzler and Grinnell, 1977).…”

“…Noseleaves appear to function in directing nasally emitted echolocation calls (Fenton, 1984(Fenton, , 1985Novick, 1977), but few studies have documented the role that these structures play in echolocation or addressed how differences in noseleaf structure affect nasal emission. Hartley and Suthers (1987) investigated the role of the spear (which they termed the lancet) in Carollia perspicillata. These authors found that the spear acts to direct echolocation pulses in the vertical dimension, but does not affect emission in the horizontal dimension.…”

Bats Sonar Calls and its Application in Sonar Systems

“…Noseleaf acts as acoustic lens, focusing the sound into a narrow beam, which cause increasing of directionality of emitted calls and enhanced echolocation performance. The experiments with Carollia perspicillata indicated that if the noseleaf is removed, the vertical beam width increased from 60 to 120 [deg] Hartley & Suthers (1987). Fig.…”

“…If it's half of the wavelength of the emitted frequency, the sound energy straight ahead will be intensified, and attenuated on either side, resulting in a narrowing of the sound beam. Experiments with a leaf-nose bat Carollia perspicillata (family Phyllostomidae) showed that when one of the two nostrils is blocked the extend of the sound beam doubles in the horizontal plane Fig. (1) Hartley & Suthers (1987). Bats using the nostrils often have complex noseleaves composed of fold of skin and cartilage.…”

“…1. The relation between the width of the sound beam and nose-leaf and nostril emission in Carollia perspicillata (adapted from Hartley & Suthers (1987)). …”