Stoeger, Angela S.Heilmann, GunnarZeppelzauer, MatthiasGanswindt, AndreHensman, SeanCharlton, Benjamin D.Saino, Nicola2013-05-022013-05-022012-11-14Stoeger AS, Heilmann G, Zeppelzauer M, Ganswindt A, Hensman S, [et al.] (2012) 'Visualizing Sound emission of elephant vocalizations: evidence for two rumble production types.' PLoS ONE 7(11): e48907. DOI:10.1371/journal.pone.00489071932-620310.1371/journal.pone.00489076507085906G-9856-2014http://hdl.handle.net/2263/21433Since two authors (Gunnar Heilman and Sean Hensman) are employed commercial companies the authors want to declare that they did not pay for using the equipment nor for doing research with the elephant at Bela Bela. Therefore, both companies had no financial interest concerning the research. The fact that these authors are employed by these companies does not alter the authors’ adherence to all the PLOS ONE policies on sharing data and materials.üšê½Movie S1 Nasal rumble-25 fps-sound: Sound visualization of a nasal rumble. This movie shows the sound emission during a nasal rumble.Movie S2 Nasal rumble-5 fps-slow-mo: Sound visualization of a nasal rumble in slow motion. This movie shows the sound emission during a nasal rumble in slow motion (5 frames per second).Movie S3 Oral rumble-25 fps-sound: Sound visualization of an oral rumble. This movie shows the sound emission during an oral rumble.Movie S4 Oral rumble-5 fps-slow-mo: Sound visualization of an oral rumble in slow motion. This movie shows the sound emission during an oral rumble in slow motion (5 frames per second).Figure S1 Spectrograms and power spectra presenting two examples of rumbling vocalizations from a 29 year old female African elephant (Drumbo) recorded at the Vienna Zoo in 2003. Recordings were captured with a condenser microphone AKG 480 B CK 62 and a DA-P1 DAT recorder. Figures A and B show a rumble recorded during spatial separation from a part of the group, and display the formant structure of a typical nasal rumble. Figures C and D show a rumble recorded during a bonding situation when the group was reunited, and resemble an orally emitted rumble based on the observed formant values.Figure S2 Spectrograms and power spectra to show examples of rumbles from a 43 year old female African elephant (Jumbo) recorded at the Vienna Zoo in 2003 (using the same equipment as described in Figure S1). Figures A and B also show a rumble recorded during spatial separation from the group, again with the formant structure of a typical nasal rumble. Figures C and D show a rumble recorded during the bonding situation when the group was reunited, again resembling an orally emitted rumble based on the formant values. Jumbo died in 2004 and her oral vocal tract was measuring at 93 cm (Weissengruber, personal communication). The formants 1 and 2 of the oral vocal tract would thus be (using equation 3) 92 Hz and 277 Hz, which corresponds very well with the formant location observed in Figures C and D.Conceived and designed the experiments: ASS GH. Performed the experiments: ASS GH SH AG. Analyzed the data: ASS MZ. Contributed reagents/materials/analysis tools: ASS MZ. Wrote the paper: ASS BDC.Recent comparative data reveal that formant frequencies are cues to body size in animals, due to a close relationship between formant frequency spacing, vocal tract length and overall body size. Accordingly, intriguing morphological adaptations to elongate the vocal tract in order to lower formants occur in several species, with the size exaggeration hypothesis being proposed to justify most of these observations. While the elephant trunk is strongly implicated to account for the low formants of elephant rumbles, it is unknown whether elephants emit these vocalizations exclusively through the trunk, or whether the mouth is also involved in rumble production. In this study we used a sound visualization method (an acoustic camera) to record rumbles of five captive African elephants during spatial separation and subsequent bonding situations. Our results showed that the female elephants in our analysis produced two distinct types of rumble vocalizations based on vocal path differences: a nasally- and an orally-emitted rumble. Interestingly, nasal rumbles predominated during contact calling, whereas oral rumbles were mainly produced in bonding situations. In addition, nasal and oral rumbles varied considerably in their acoustic structure. In particular, the values of the first two formants reflected the estimated lengths of the vocal paths, corresponding to a vocal tract length of around 2 meters for nasal, and around 0.7 meters for oral rumbles. These results suggest that African elephants may be switching vocal paths to actively vary vocal tract length (with considerable variation in formants) according to context, and call for further research investigating the function of formant modulation in elephant vocalizations. Furthermore, by confirming the use of the elephant trunk in long distance rumble production, our findings provide an explanation for the extremely low formants in these calls, and may also indicate that formant lowering functions to increase call propagation distances in this species’.8 pagesPDFen© 2012 Stoeger et al. This is an open-access article distributed under the terms of the Creative Commons Attribution LicenseElephantsSound emissionRumble vocalizationsLoxodonta africanaSound production by animalsAfrican elephant -- VocalizationArticle