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Angela S. Stoeger
Mammal Communication Lab, Department of Behavioral & Cognitive Biology University of Vienna Vienna Austria

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Short Biography

Angela Stoeger received her Master's in Zoology in 2002 and her PhD (honored with the Doc.Award) in 2006 at the University of Vienna. She established the Mammal Communication Lab and is working as PI and lab leader at the Department of Behavioral and Cognitive Biology, University of Vienna. Angela uses communication as a tool to study cognition, allowing her to design formal and natural experiments to test specific hypotheses. Her current research focuses on various aspects of mammal communication (with elephants L. africana and E. maximus as the main current model species), particularly investigating sound production and perception mechanisms and vocal learning.

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Research article
Published: 16 August 2021 in Zoo Biology
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The social and cooperative behavior of meerkats (Suricata suricatta), specifically their sentinel behavior, has been intensively studied in free-ranging populations. This study focuses on whether guarding in captive meerkats exhibits a pattern similar to that described for wild groups. Sentinel behavior in captivity has been somewhat neglected because predation is usually not a critical factor. Nonetheless, observations in captivity might reveal whether individual or group experience influences this specific behavior pattern. We observed three captive meerkat groups (in outdoor as well as indoor enclosures) and analyzed the duration of guarding sequences, the number of established guards, the guard posture, and the individual guard positions. We also conducted playback experiments to investigate the reaction of the sentinel and the group to bird calls (songbird vs. predatory bird species). The results demonstrated that captive groups behave much the same as wild groups. Certain individuals performed the guard job more often than other group members. Accordingly, the “super sentinels” observed in the wild also exist in captive groups. Playbacks showed that the sentinels reacted more strongly to the calls of predatory bird species, indicating that captive meerkats are able to categorize bird calls. We also documented major differences in behavioral responses to the calls of specific predatory bird species. Our observations underline that sentinel behavior is probably a combination of an innate, imprinted pattern that is further affected by the experience. Future studies might further investigate this influence of experience, beyond innate behavior, on the group-specific sentinel behavior pattern in captive meerkats.

ACS Style

Florian D. Huels; Angela S. Stoeger. Sentinel behavior in captive meerkats ( Suricata suricatta ). Zoo Biology 2021, 1 .

AMA Style

Florian D. Huels, Angela S. Stoeger. Sentinel behavior in captive meerkats ( Suricata suricatta ). Zoo Biology. 2021; ():1.

Chicago/Turabian Style

Florian D. Huels; Angela S. Stoeger. 2021. "Sentinel behavior in captive meerkats ( Suricata suricatta )." Zoo Biology , no. : 1.

Journal article
Published: 05 August 2021 in Biology
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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.

ACS Style

Angela Stoeger; Anton Baotic; Gunnar Heilmann. Vocal Creativity in Elephant Sound Production. Biology 2021, 10, 750 .

AMA Style

Angela Stoeger, Anton Baotic, Gunnar Heilmann. Vocal Creativity in Elephant Sound Production. Biology. 2021; 10 (8):750.

Chicago/Turabian Style

Angela Stoeger; Anton Baotic; Gunnar Heilmann. 2021. "Vocal Creativity in Elephant Sound Production." Biology 10, no. 8: 750.

Journal article
Published: 17 June 2021 in BMC Biology
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Background Anatomical and cognitive adaptations to overcome morpho-mechanical limitations of laryngeal sound production, where body size and the related vocal apparatus dimensions determine the fundamental frequency, increase vocal diversity across taxa. Elephants flexibly use laryngeal and trunk-based vocalizations to form a repertoire ranging from infrasonic rumbles to higher-pitched trumpets. Moreover, they are among the few evolutionarily distantly related animals (humans, pinnipeds, cetaceans, birds) capable of imitating species-atypical sounds. Yet, their vocal plasticity has so far not been related to functions within their natural communicative system, in part because not all call types have been systematically studied. Here, we reveal how Asian elephants (Elephas maximus) produce species-specific squeaks (F0 300–2300 Hz) by using acoustic camera recordings to visualize sound emission and examining this alongside acoustic, behavioral, and morphological data across seven captive groups. Results We found that squeaks were emitted through the closed mouth in synchrony with cheek depression and retraction of the labial angles. The simultaneous emission of squeaks with nasal snorts (biphonation) in one individual confirmed that squeak production was independent of nasal passage involvement and this implicated oral sound production. The squeaks’ spectral structure is incongruent with laryngeal sound production and aerodynamic whistles, pointing to tissue vibration as the sound source. Anatomical considerations suggest that the longitudinal closed lips function as the vibrators. Acoustic and temporal parameters exhibit high intra- and inter-individual variability that enables individual but no call-subtype classification. Only 19 of 56 study subjects were recorded to squeak, mostly during alarming contexts and social arousal but some also on command. Conclusion Our results strongly suggest that Asian elephants force air from the small oral cavity through the tensed lips, inducing self-sustained lip vibration. Besides human brass players, lip buzzing is not described elsewhere in the animal kingdom. Given the complexity of the proposed mechanism, the surprising absence of squeaking in most of the unrelated subjects and the indication for volitional control, we hypothesize that squeak production involves social learning. Our study offers new insights into how vocal and cognitive flexibility enables mammals to overcome size-related limitations of laryngeal sound production. This flexibility enables Asian elephants to exploit a frequency range spanning seven octaves within their communicative system.

ACS Style

Veronika C. Beeck; Gunnar Heilmann; Michael Kerscher; Angela S. Stoeger. A novel theory of Asian elephant high-frequency squeak production. BMC Biology 2021, 19, 1 -16.

AMA Style

Veronika C. Beeck, Gunnar Heilmann, Michael Kerscher, Angela S. Stoeger. A novel theory of Asian elephant high-frequency squeak production. BMC Biology. 2021; 19 (1):1-16.

Chicago/Turabian Style

Veronika C. Beeck; Gunnar Heilmann; Michael Kerscher; Angela S. Stoeger. 2021. "A novel theory of Asian elephant high-frequency squeak production." BMC Biology 19, no. 1: 1-16.

Journal article
Published: 23 February 2019 in Behavioral Ecology
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Michael A Pardo; Joyce H Poole; Angela S Stoeger; Peter H Wrege; Caitlin E O’Connell-Rodwell; Udaha Kapugedara Padmalal; Shermin De Silva. Differences in combinatorial calls among the 3 elephant species cannot be explained by phylogeny. Behavioral Ecology 2019, 30, 809 -820.

AMA Style

Michael A Pardo, Joyce H Poole, Angela S Stoeger, Peter H Wrege, Caitlin E O’Connell-Rodwell, Udaha Kapugedara Padmalal, Shermin De Silva. Differences in combinatorial calls among the 3 elephant species cannot be explained by phylogeny. Behavioral Ecology. 2019; 30 (3):809-820.

Chicago/Turabian Style

Michael A Pardo; Joyce H Poole; Angela S Stoeger; Peter H Wrege; Caitlin E O’Connell-Rodwell; Udaha Kapugedara Padmalal; Shermin De Silva. 2019. "Differences in combinatorial calls among the 3 elephant species cannot be explained by phylogeny." Behavioral Ecology 30, no. 3: 809-820.

Journal article
Published: 30 September 2018 in Animals
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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.

ACS Style

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 Style

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 (10):167.

Chicago/Turabian Style

Anton 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.

Research article
Published: 10 May 2017 in PLOS ONE
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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.

ACS Style

Anton Baotic; Angela S. Stoeger. Sexual dimorphism in African elephant social rumbles. PLOS ONE 2017, 12, e0177411 .

AMA Style

Anton Baotic, Angela S. Stoeger. Sexual dimorphism in African elephant social rumbles. PLOS ONE. 2017; 12 (5):e0177411.

Chicago/Turabian Style

Anton Baotic; Angela S. Stoeger. 2017. "Sexual dimorphism in African elephant social rumbles." PLOS ONE 12, no. 5: e0177411.

Journal article
Published: 19 April 2017 in Scientific Reports
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Gaining information about conspecifics via long-distance vocalizations is crucial for social and spatially flexible species such as the African elephant (Loxodonta africana). Female elephants are known to discriminate individuals and kin based on acoustic cues. Specifically, females approached the loudspeaker exclusively with playbacks of familiar individuals with high association indexes, intentionally fusing with their affiliates. For males, which are less bonded, gathering social information via vocalizations could still have important implications, but little is known about their vocal discrimination skills. We experimentally tested the ability of male African elephants to discriminate the social rumbles of familiar (from the same population) versus unfamiliar females. Male elephants discriminated and preferentially moved towards the rumbles of unfamiliar females, showing longer attentive reactions and significantly more orientating (facing and approaching the speaker) behavior. The increased orientating response of males towards playbacks of unfamiliar females is converse to the reaction of female subjects. Our results provide evidence that male elephants extract social information from vocalizations, yet with a different intention than females. Accordingly, males might use social cues in vocalizations to assess mating opportunities, which may involve selection to identify individuals or kin in order to avoid inbreeding.

ACS Style

Angela S. Stoeger; Anton Baotic. Male African elephants discriminate and prefer vocalizations of unfamiliar females. Scientific Reports 2017, 7, 46414 .

AMA Style

Angela S. Stoeger, Anton Baotic. Male African elephants discriminate and prefer vocalizations of unfamiliar females. Scientific Reports. 2017; 7 (1):46414.

Chicago/Turabian Style

Angela S. Stoeger; Anton Baotic. 2017. "Male African elephants discriminate and prefer vocalizations of unfamiliar females." Scientific Reports 7, no. 1: 46414.

Perspective article
Published: 20 June 2016 in Frontiers in Neuroscience
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Research on the evolution of human speech and music benefits from hypotheses and data generated in a number of disciplines. The purpose of this article is to illustrate the high relevance of pinniped research for the study of speech, musical rhythm, and their human origins, bridging current research with primates and birds. We briefly discuss speech, vocal learning and rhythm from an evolutionary, comparative perspective. We review the current state of knowledge on pinniped communication and behaviour relevant to the evolution of human speech and music, showing interesting parallels to hypotheses on rhythmic behaviour in early hominids. We suggest future research directions in terms of species to test and empirical data needed.

ACS Style

Andrea Ravignani; W. Tecumseh Fitch; Frederike D. Hanke; Tamara Heinrich; Bettina Hurgitsch; Sonja A. Kotz; Constance Scharff; Angela S. Stoeger; Bart de Boer. What Pinnipeds Have to Say about Human Speech, Music, and the Evolution of Rhythm. Frontiers in Neuroscience 2016, 10, 274 .

AMA Style

Andrea Ravignani, W. Tecumseh Fitch, Frederike D. Hanke, Tamara Heinrich, Bettina Hurgitsch, Sonja A. Kotz, Constance Scharff, Angela S. Stoeger, Bart de Boer. What Pinnipeds Have to Say about Human Speech, Music, and the Evolution of Rhythm. Frontiers in Neuroscience. 2016; 10 ():274.

Chicago/Turabian Style

Andrea Ravignani; W. Tecumseh Fitch; Frederike D. Hanke; Tamara Heinrich; Bettina Hurgitsch; Sonja A. Kotz; Constance Scharff; Angela S. Stoeger; Bart de Boer. 2016. "What Pinnipeds Have to Say about Human Speech, Music, and the Evolution of Rhythm." Frontiers in Neuroscience 10, no. : 274.

Journal article
Published: 08 June 2016 in Scientific Reports
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Until recently, the prevailing theory about male African elephants (Loxodonta africana) was that, once adult and sexually mature, males are solitary and targeted only at finding estrous females. While this is true during the state of ‘musth’ (a condition characterized by aggressive behavior and elevated androgen levels), ‘non-musth’ males exhibit a social system seemingly based on companionship, dominance and established hierarchies. Research on elephant vocal communication has so far focused on females, and very little is known about the acoustic structure and the information content of male vocalizations. Using the source and filter theory approach, we analyzed social rumbles of 10 male African elephants. Our results reveal that male rumbles encode information about individuality and maturity (age and size), with formant frequencies and absolute fundamental frequency values having the most informative power. This first comprehensive study on male elephant vocalizations gives important indications on their potential functional relevance for male-male and male-female communication. Our results suggest that, similar to the highly social females, future research on male elephant vocal behavior will reveal a complex communication system in which social knowledge, companionship, hierarchy, reproductive competition and the need to communicate over long distances play key roles.

ACS Style

Angela S. Stoeger; Anton Baotic. Information content and acoustic structure of male African elephant social rumbles. Scientific Reports 2016, 6, 27585 .

AMA Style

Angela S. Stoeger, Anton Baotic. Information content and acoustic structure of male African elephant social rumbles. Scientific Reports. 2016; 6 (1):27585.

Chicago/Turabian Style

Angela S. Stoeger; Anton Baotic. 2016. "Information content and acoustic structure of male African elephant social rumbles." Scientific Reports 6, no. 1: 27585.

Book chapter
Published: 28 April 2016 in Springer Handbook of Auditory Research
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Infrasonic and seismic communication in terrestrial vertebrates is generally poorly known. Moreover, studies of these communication modalities have been restricted to relatively few vertebrate groups. In this chapter we begin with the non-Afrotherian vertebrates and review what is known about their infrasonic (including birds and mammals) and seismic (including amphibians, reptiles, birds, and mammals) communication. We then devote special sections to the Afrotherian vertebrates, concentrating on (1) infrasonic communication in elephants, (2) seismic communication in elephants, and (3) seismic communication in golden moles (Chrysocloridae). Motivated by the lack of detailed knowledge of vibration communication in chrysochlorids, we furnish a blueprint for a set of experiments that would provide novel and interesting data to fill the lacunae in our understanding of seismic signal detection and localization by these enigmatic animals.

ACS Style

Peter M. Narins; Angela S. Stoeger; Caitlin O’Connell-Rodwell. Infrasonic and Seismic Communication in the Vertebrates with Special Emphasis on the Afrotheria: An Update and Future Directions. Springer Handbook of Auditory Research 2016, 191 -227.

AMA Style

Peter M. Narins, Angela S. Stoeger, Caitlin O’Connell-Rodwell. Infrasonic and Seismic Communication in the Vertebrates with Special Emphasis on the Afrotheria: An Update and Future Directions. Springer Handbook of Auditory Research. 2016; ():191-227.

Chicago/Turabian Style

Peter M. Narins; Angela S. Stoeger; Caitlin O’Connell-Rodwell. 2016. "Infrasonic and Seismic Communication in the Vertebrates with Special Emphasis on the Afrotheria: An Update and Future Directions." Springer Handbook of Auditory Research , no. : 191-227.

Short report
Published: 09 September 2015 in BMC Research Notes
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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.

ACS Style

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 Style

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):1-11.

Chicago/Turabian Style

Anton 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.

Project note
Published: 04 September 2015 in BMC Research Notes
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The decline of habitat for elephants due to expanding human activity is a serious conservation problem. This has continuously escalated the human-elephant conflict in Africa and Asia. Elephants make extensive use of powerful infrasonic calls (rumbles) that travel distances of up to several kilometers. This makes elephants well-suited for acoustic monitoring because it enables detecting elephants even if they are out of sight. In sight, their distinct visual appearance makes them a good candidate for visual monitoring. We provide an integrated overview of our interdisciplinary project that established the scientific fundamentals for a future early warning and monitoring system for humans who regularly experience serious conflict with elephants. We first draw the big picture of an early warning and monitoring system, then review the developed solutions for automatic acoustic and visual detection, discuss specific challenges and present open future work necessary to build a robust and reliable early warning and monitoring system that is able to operate in situ. We present a method for the automated detection of elephant rumbles that is robust to the diverse noise sources present in situ. We evaluated the method on an extensive set of audio data recorded under natural field conditions. Results show that the proposed method outperforms existing approaches and accurately detects elephant rumbles. Our visual detection method shows that tracking elephants in wildlife videos (of different sizes and postures) is feasible and particularly robust at near distances. From our project results we draw a number of conclusions that are discussed and summarized. We clearly identified the most critical challenges and necessary improvements of the proposed detection methods and conclude that our findings have the potential to form the basis for a future automated early warning system for elephants. We discuss challenges that need to be solved and summarize open topics in the context of a future early warning and monitoring system. We conclude that a long-term evaluation of the presented methods in situ using real-time prototypes is the most important next step to transfer the developed methods into practical implementation.

ACS Style

Matthias Zeppelzauer; Angela S. Stoeger. Establishing the fundamentals for an elephant early warning and monitoring system. BMC Research Notes 2015, 8, 409 .

AMA Style

Matthias Zeppelzauer, Angela S. Stoeger. Establishing the fundamentals for an elephant early warning and monitoring system. BMC Research Notes. 2015; 8 (1):409.

Chicago/Turabian Style

Matthias Zeppelzauer; Angela S. Stoeger. 2015. "Establishing the fundamentals for an elephant early warning and monitoring system." BMC Research Notes 8, no. 1: 409.

Review article
Published: 23 July 2014 in Current Opinion in Neurobiology
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In the last decade clear evidence has accumulated that elephants are capable of vocal production learning. Examples of vocal imitation are documented in African (Loxodonta africana) and Asian (Elephas maximus) elephants, but little is known about the function of vocal learning within the natural communication systems of either species. We are also just starting to identify the neural basis of elephant vocalizations. The African elephant diencephalon and brainstem possess specializations related to aspects of neural information processing in the motor system (affecting the timing and learning of trunk movements) and the auditory and vocalization system. Comparative interdisciplinary (from behavioral to neuroanatomical) studies are strongly warranted to increase our understanding of both vocal learning and vocal behavior in elephants.

ACS Style

Angela S Stoeger; Paul Manger. Vocal learning in elephants: neural bases and adaptive context. Current Opinion in Neurobiology 2014, 28, 101 -107.

AMA Style

Angela S Stoeger, Paul Manger. Vocal learning in elephants: neural bases and adaptive context. Current Opinion in Neurobiology. 2014; 28 ():101-107.

Chicago/Turabian Style

Angela S Stoeger; Paul Manger. 2014. "Vocal learning in elephants: neural bases and adaptive context." Current Opinion in Neurobiology 28, no. : 101-107.

Articles
Published: 22 April 2014 in Bioacoustics
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The human-elephant conflict is one of the most serious conservation problems in Asia and Africa today. The involuntary confrontation of humans and elephants claims the lives of many animals and humans every year. A promising approach to alleviate this conflict is the development of an acoustic early warning system. Such a system requires the robust automated detection of elephant vocalizations under unconstrained field conditions. Today, no system exists that fulfills these requirements. In this paper, we present a method for the automated detection of elephant vocalizations that is robust to the diverse noise sources present in the field. We evaluate the method on a dataset recorded under natural field conditions to simulate a real-world scenario. The proposed method outperformed existing approaches and robustly and accurately detected elephants. It thus can form the basis for a future automated early warning system for elephants. Furthermore, the method may be a useful tool for scientists in bioacoustics for the study of wildlife recordings.

ACS Style

Matthias Zeppelzauer; Sean Hensman; Angela S. Stoeger. Towards an automated acoustic detection system for free-ranging elephants. Bioacoustics 2014, 24, 13 -29.

AMA Style

Matthias Zeppelzauer, Sean Hensman, Angela S. Stoeger. Towards an automated acoustic detection system for free-ranging elephants. Bioacoustics. 2014; 24 (1):13-29.

Chicago/Turabian Style

Matthias Zeppelzauer; Sean Hensman; Angela S. Stoeger. 2014. "Towards an automated acoustic detection system for free-ranging elephants." Bioacoustics 24, no. 1: 13-29.

Journal article
Published: 09 April 2014 in Bioacoustics
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We used vocal indicators to examine the effect of a translocation of an African elephant family herd within the Kruger National Park (KNP). These animals were moved 300 km from their home range, but returned unaided to this range within 23 days. We found that translocation resulted in a change in the mean fundamental frequency of lowfrequency elephant vocalizations, known as rumbles. The rumbles increased significantly in pitch compared to pre-translocation levels during the 23 days the animals spent outside their normal home range. Mean fundamental frequency returned close to pre-translocation level by the time the animals had navigated their way back to their previous home range. Raised pitch is known to be an indicator of stress in humans and other animals. The observed acoustic results are consistent with a physiological measure of stress, faecal glucocorticoid metabolite (FGM) levels, which were monitored of the same animals during the study and have already been reported elsewere. This, to our knowledge, is the first report of prolonged monitoring of vocal stress response in free-ranging animals. Measuring behavioural responses, such as vocalizations, may provide an objective non-invasive method for assessing stress. This could help in determining the effects that particular management actions might have on elephants.Pittsburgh Zoo & PPG Aquarium and SANParks,http://www.tandfonline.com/loi/tbio20hb201

ACS Style

Jozua Jakobus Viljoen; Andre Ganswindt; Christopher Reynecke; Angela S Stoeger; William Richard Langbauer. Vocal stress associated with a translocation of a family herd of African elephants (Loxodonta africana) in the Kruger National Park, South Africa. Bioacoustics 2014, 24, 1 -12.

AMA Style

Jozua Jakobus Viljoen, Andre Ganswindt, Christopher Reynecke, Angela S Stoeger, William Richard Langbauer. Vocal stress associated with a translocation of a family herd of African elephants (Loxodonta africana) in the Kruger National Park, South Africa. Bioacoustics. 2014; 24 (1):1-12.

Chicago/Turabian Style

Jozua Jakobus Viljoen; Andre Ganswindt; Christopher Reynecke; Angela S Stoeger; William Richard Langbauer. 2014. "Vocal stress associated with a translocation of a family herd of African elephants (Loxodonta africana) in the Kruger National Park, South Africa." Bioacoustics 24, no. 1: 1-12.

Comparative study
Published: 01 November 2013 in Journal of Experimental Biology
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SUMMARY Elephants' low-frequency vocalizations are produced by flow-induced self-sustaining oscillations of laryngeal tissue. To date, little is known in detail about the vibratory phenomena in the elephant larynx. Here, we provide a first descriptive report of the complex oscillatory features found in the excised larynx of a 25 year old female African elephant (Loxodonta africana), the largest animal sound generator ever studied experimentally. Sound production was documented with high-speed video, acoustic measurements, air flow and sound pressure level recordings. The anatomy of the larynx was studied with computed tomography (CT) and dissections. Elephant CT vocal anatomy data were further compared with the anatomy of an adult human male. We observed numerous unusual phenomena, not typically reported in human vocal fold vibrations. Phase delays along both the inferior–superior and anterior–posterior (A–P) dimension were commonly observed, as well as transverse travelling wave patterns along the A–P dimension, previously not documented in the literature. Acoustic energy was mainly created during the instant of glottal opening. The vestibular folds, when adducted, participated in tissue vibration, effectively increasing the generated sound pressure level by 12 dB. The complexity of the observed phenomena is partly attributed to the distinct laryngeal anatomy of the elephant larynx, which is not simply a large-scale version of its human counterpart. Travelling waves may be facilitated by low fundamental frequencies and increased vocal fold tension. A travelling wave model is proposed, to account for three types of phenomena: A–P travelling waves, ‘conventional’ standing wave patterns, and irregular vocal fold vibration.

ACS Style

Christian Herbst; Jan G. Svec; Jörg Lohscheller; Roland Frey; Michaela Gumpenberger; Angela S Stoeger; W. Tecumseh Fitch. Complex vibratory patterns in an elephant larynx. Journal of Experimental Biology 2013, 216, 4054 -4064.

AMA Style

Christian Herbst, Jan G. Svec, Jörg Lohscheller, Roland Frey, Michaela Gumpenberger, Angela S Stoeger, W. Tecumseh Fitch. Complex vibratory patterns in an elephant larynx. Journal of Experimental Biology. 2013; 216 (21):4054-4064.

Chicago/Turabian Style

Christian Herbst; Jan G. Svec; Jörg Lohscheller; Roland Frey; Michaela Gumpenberger; Angela S Stoeger; W. Tecumseh Fitch. 2013. "Complex vibratory patterns in an elephant larynx." Journal of Experimental Biology 216, no. 21: 4054-4064.

Journal article
Published: 18 October 2013 in Bioacoustics
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Animal vocal signals are increasingly used to monitor wildlife populations and to obtain estimates of species occurrence and abundance. In the future, acoustic monitoring should function not only to detect animals, but also to extract detailed information about populations by discriminating sexes, age groups, social or kin groups, and potentially individuals. Here we show that it is possible to estimate age groups of African elephants (Loxodonta africana) based on acoustic parameters extracted from rumbles recorded under field conditions in a National Park in South Africa. Statistical models reached up to 70 % correct classification to four age groups (infants, calves, juveniles, adults) and 95 % correct classification when categorising into two groups (infants/calves lumped into one group versus adults). The models revealed that parameters representing absolute frequency values have the most discriminative power. Comparable classification results were obtained by fully automated classification of rumbles by high-dimensional features that represent the entire spectral envelope, such as MFCC (75 % correct classification) and GFCC (74 % correct classification). The reported results and methods provide the scientific foundation for a future system that could potentially automatically estimate the demography of an acoustically monitored elephant group or population.

ACS Style

Angela S. Stoeger; Matthias Zeppelzauer; Anton Baotic. Age-group estimation in free-ranging African elephants based on acoustic cues of low-frequency rumbles. Bioacoustics 2013, 23, 231 -246.

AMA Style

Angela S. Stoeger, Matthias Zeppelzauer, Anton Baotic. Age-group estimation in free-ranging African elephants based on acoustic cues of low-frequency rumbles. Bioacoustics. 2013; 23 (3):231-246.

Chicago/Turabian Style

Angela S. Stoeger; Matthias Zeppelzauer; Anton Baotic. 2013. "Age-group estimation in free-ranging African elephants based on acoustic cues of low-frequency rumbles." Bioacoustics 23, no. 3: 231-246.

Book chapter
Published: 21 August 2013 in Biocommunication of Animals
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Although living in substantially different habitats, African (Loxodonta sp.) and Asian (Elephas maximus) elephants are extremely social and intra-specific communication is therefore highly developed in these species. In particular, elephants are very vocal and acoustic signals play an integral part within the society of African and Asian elephants. In this chapter, we provide a cross-species comparison of the African savannah elephant (L. africana) and Asian elephant vocal communication systems, discussing the acoustic structure of various call types, examples of vocal imitation and sound production mechanisms. We aim to explore what the similarities and differences in the communication system of the two species could reveal about call functions, and the ecological conditions that have shaped these communication systems. In light of this, we suggest future comparative investigations of African and Asian elephants that may provide deeper insights into the evolutionary and cognitive bases of the complex signalling mechanisms.

ACS Style

Angela S. Stoeger; Shermin de Silva. African and Asian Elephant Vocal Communication: A Cross-Species Comparison. Biocommunication of Animals 2013, 21 -39.

AMA Style

Angela S. Stoeger, Shermin de Silva. African and Asian Elephant Vocal Communication: A Cross-Species Comparison. Biocommunication of Animals. 2013; ():21-39.

Chicago/Turabian Style

Angela S. Stoeger; Shermin de Silva. 2013. "African and Asian Elephant Vocal Communication: A Cross-Species Comparison." Biocommunication of Animals , no. : 21-39.

Journal article
Published: 22 May 2013 in Bioacoustics
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ACS Style

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 Style

Anton 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 Style

Anton 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.

Conference paper
Published: 01 January 2013 in Proceedings of the 2nd ACM international workshop on Multimedia analysis for ecological data - MAED '13
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The automated acoustic detection of elephants is an important factor in alleviating the human-elephant conflict in Asia and Africa. In this paper, we present a method for the automated detection of elephant presence and evaluate it on a large dataset of wildlife recordings. We introduce a novel technique for signal enhancement to improve the robustness of the detector in noisy situations. Experiments show that the proposed detector outperforms existing methods and that signal enhancement strongly improves the robustness to noise sources from the environment. The proposed method is a first step towards an automated detection system for elephant presence.

ACS Style

Matthias Zeppelzauer; Angela S. Stöger; Christian Breiteneder. Acoustic detection of elephant presence in noisy environments. Proceedings of the 2nd ACM international workshop on Multimedia analysis for ecological data - MAED '13 2013, 3 -8.

AMA Style

Matthias Zeppelzauer, Angela S. Stöger, Christian Breiteneder. Acoustic detection of elephant presence in noisy environments. Proceedings of the 2nd ACM international workshop on Multimedia analysis for ecological data - MAED '13. 2013; ():3-8.

Chicago/Turabian Style

Matthias Zeppelzauer; Angela S. Stöger; Christian Breiteneder. 2013. "Acoustic detection of elephant presence in noisy environments." Proceedings of the 2nd ACM international workshop on Multimedia analysis for ecological data - MAED '13 , no. : 3-8.