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How do elephants achieve their enormous vocal flexibility when communicating, imitating or creating idiosyncratic sounds? The mechanisms that underpin this trait combine motoric abilities with vocal learning processes. We demonstrate the unusual production techniques used by five African savanna elephants to create idiosyncratic sounds, which they learn to produce on cue by positive reinforcement training. The elephants generate these sounds by applying nasal tissue vibration via an ingressive airflow at the trunk tip, or by contracting defined superficial muscles at the trunk base. While the production mechanisms of the individuals performing the same sound categories are similar, they do vary in fine-tuning, revealing that each individual has its own specific sound-producing strategy. This plasticity reflects the creative and cognitive abilities associated with ‘vocal’ learning processes. The fact that these sounds were reinforced and cue-stimulated suggests that social feedback and positive reinforcement can facilitate vocal creativity and vocal learning behavior in elephants. Revealing the mechanism and the capacity for vocal learning and sound creativity is fundamental to understanding the eloquence within the elephants’ communication system. This also helps to understand the evolution of human language and of open-ended vocal systems, which build upon similar cognitive processes.
Angela Stoeger; Anton Baotic; Gunnar Heilmann. Vocal Creativity in Elephant Sound Production. Biology 2021, 10, 750 .
AMA StyleAngela Stoeger, Anton Baotic, Gunnar Heilmann. Vocal Creativity in Elephant Sound Production. Biology. 2021; 10 (8):750.
Chicago/Turabian StyleAngela Stoeger; Anton Baotic; Gunnar Heilmann. 2021. "Vocal Creativity in Elephant Sound Production." Biology 10, no. 8: 750.
African savanna elephants live in dynamic fission–fusion societies and exhibit a sophisticated vocal communication system. Their most frequent call-type is the ‘rumble’, with a fundamental frequency (which refers to the lowest vocal fold vibration rate when producing a vocalization) near or in the infrasonic range. Rumbles are used in a wide variety of behavioral contexts, for short- and long-distance communication, and convey contextual and physical information. For example, maturity (age and size) is encoded in male rumbles by formant frequencies (the resonance frequencies of the vocal tract), having the most informative power. As sound propagates, however, its spectral and temporal structures degrade progressively. Our study used manipulated and resynthesized male social rumbles to simulate large and small individuals (based on different formant values) to quantify whether this phenotypic information efficiently transmits over long distances. To examine transmission efficiency and the potential influences of ecological factors, we broadcasted and re-recorded rumbles at distances of up to 1.5 km in two different habitats at the Addo Elephant National Park, South Africa. Our results show that rumbles were affected by spectral–temporal degradation over distance. Interestingly and unlike previous findings, the transmission of formants was better than that of the fundamental frequency. Our findings demonstrate the importance of formant frequencies for the efficiency of rumble propagation and the transmission of information content in a savanna elephant’s natural habitat.
Anton Baotic; Maxime Garcia; Markus Boeckle; Angela Stoeger. Field Propagation Experiments of Male African Savanna Elephant Rumbles: A Focus on the Transmission of Formant Frequencies. Animals 2018, 8, 167 .
AMA StyleAnton Baotic, Maxime Garcia, Markus Boeckle, Angela Stoeger. Field Propagation Experiments of Male African Savanna Elephant Rumbles: A Focus on the Transmission of Formant Frequencies. Animals. 2018; 8 (10):167.
Chicago/Turabian StyleAnton Baotic; Maxime Garcia; Markus Boeckle; Angela Stoeger. 2018. "Field Propagation Experiments of Male African Savanna Elephant Rumbles: A Focus on the Transmission of Formant Frequencies." Animals 8, no. 10: 167.
This study used the source and filter theory approach to analyse sex differences in the acoustic features of African elephant (Loxodonta africana) low-frequency rumbles produced in social contexts (‘social rumbles’). Permuted discriminant function analysis revealed that rumbles contain sufficient acoustic information to predict the sex of a vocalizing individual. Features primarily related to the vocalizer’s size, i.e. fundamental frequency variables and vocal tract resonant frequencies, differed significantly between the sexes. Yet, controlling for age and size effects, our results indicate that the pronounced sexual size dimorphism in African elephants is partly, but not exclusively, responsible for sexual differences in social rumbles. This provides a scientific foundation for future work investigating the perceptual and functional relevance of specific acoustic characteristics in African elephant vocal sexual communication.
Anton Baotic; Angela S. Stoeger. Sexual dimorphism in African elephant social rumbles. PLOS ONE 2017, 12, e0177411 .
AMA StyleAnton Baotic, Angela S. Stoeger. Sexual dimorphism in African elephant social rumbles. PLOS ONE. 2017; 12 (5):e0177411.
Chicago/Turabian StyleAnton Baotic; Angela S. Stoeger. 2017. "Sexual dimorphism in African elephant social rumbles." PLOS ONE 12, no. 5: e0177411.
Recent research reveals that giraffes (Giraffa camelopardalis sp.) exhibit a socially structured, fission–fusion system. In other species possessing this kind of society, information exchange is important and vocal communication is usually well developed. But is this true for giraffes? Giraffes are known to produce sounds, but there is no evidence that they use vocalizations for communication. Reports on giraffe vocalizations are mainly anecdotal and the missing acoustic descriptions make it difficult to establish a call nomenclature. Despite inconclusive evidence to date, it is widely assumed that giraffes produce infrasonic vocalizations similar to elephants. In order to initiate a more detailed investigation of the vocal communication in giraffes, we collected data of captive individuals during day and night. We particularly focussed on detecting tonal, infrasonic or sustained vocalizations. We collected over 947 h of audio material in three European zoos and quantified the spectral and temporal components of acoustic signals to obtain an accurate set of acoustic parameters. Besides the known burst, snorts and grunts, we detected harmonic, sustained and frequency-modulated “humming” vocalizations during night recordings. None of the recorded vocalizations were within the infrasonic range. These results show that giraffes do produce vocalizations, which, based on their acoustic structure, might have the potential to function as communicative signals to convey information about the physical and motivational attributes of the caller. The data further reveal that the assumption of infrasonic communication in giraffes needs to be considered with caution and requires further investigations in future studies.
Anton Baotic; Florian Sicks; Angela S. Stoeger. Nocturnal “humming” vocalizations: adding a piece to the puzzle of giraffe vocal communication. BMC Research Notes 2015, 8, 1 -11.
AMA StyleAnton Baotic, Florian Sicks, Angela S. Stoeger. Nocturnal “humming” vocalizations: adding a piece to the puzzle of giraffe vocal communication. BMC Research Notes. 2015; 8 (1):1-11.
Chicago/Turabian StyleAnton Baotic; Florian Sicks; Angela S. Stoeger. 2015. "Nocturnal “humming” vocalizations: adding a piece to the puzzle of giraffe vocal communication." BMC Research Notes 8, no. 1: 1-11.
Anton Baotic; Angela S Stoeger; Desheng Li; Chunxiang Tang; Benjamin Charlton. The vocal repertoire of infant giant pandas (Ailuropoda melanoleuca). Bioacoustics 2013, 23, 15 -28.
AMA StyleAnton Baotic, Angela S Stoeger, Desheng Li, Chunxiang Tang, Benjamin Charlton. The vocal repertoire of infant giant pandas (Ailuropoda melanoleuca). Bioacoustics. 2013; 23 (1):15-28.
Chicago/Turabian StyleAnton Baotic; Angela S Stoeger; Desheng Li; Chunxiang Tang; Benjamin Charlton. 2013. "The vocal repertoire of infant giant pandas (Ailuropoda melanoleuca)." Bioacoustics 23, no. 1: 15-28.
Infant giant pandas are highly vocal during the first few weeks of life, producing vocalisations that are characterised by noisy, aperiodic segments. The aperiodic character of many animal vocalisations results from irregular vibratory regimes of the vocal folds, and one proposed function of this so‐called nonlinear phenomena (NLP) in animal vocalisations is to convey information about the caller's arousal state. This hypothesis was tested in the vocalisations of six hand‐reared giant panda cubs recorded during handling and feeding procedures that had been categorised into low‐ and high‐arousal contexts based on quantified motor activity. Ninety‐three per cent of the vocalisations contained NLP, including deterministic chaos and subharmonics. Vocalisations produced in the high‐arousal contexts, however, were characterised by an increase in chaos, as well as increased call duration and x fundamental frequency (pitch). These results suggest that infant giant panda vocal signals have the potential to express different arousal states. Furthermore, because giant panda cubs are the smallest placental mammal offspring at birth compared with adult size, acoustically conveying arousal state to the mother might be crucial for infant survival under natural rearing conditions.
Angela S. Stoeger; Anton Baotic; Desheng Li; Benjamin D. Charlton. Acoustic Features Indicate Arousal in Infant Giant Panda Vocalisations. Ethology 2012, 118, 896 -905.
AMA StyleAngela S. Stoeger, Anton Baotic, Desheng Li, Benjamin D. Charlton. Acoustic Features Indicate Arousal in Infant Giant Panda Vocalisations. Ethology. 2012; 118 (9):896-905.
Chicago/Turabian StyleAngela S. Stoeger; Anton Baotic; Desheng Li; Benjamin D. Charlton. 2012. "Acoustic Features Indicate Arousal in Infant Giant Panda Vocalisations." Ethology 118, no. 9: 896-905.