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Liao CC, Magrath RD, Manser MB, Farine DR. The relative contribution of acoustic signals versus movement cues in group coordination and collective decision-making. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230184. [PMID: 38768199 PMCID: PMC11391321 DOI: 10.1098/rstb.2023.0184] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 01/30/2024] [Accepted: 03/04/2024] [Indexed: 05/22/2024] Open
Abstract
To benefit from group living, individuals need to maintain cohesion and coordinate their activities. Effective communication thus becomes critical, facilitating rapid coordination of behaviours and reducing consensus costs when group members have differing needs and information. In many bird and mammal species, collective decisions rely on acoustic signals in some contexts but on movement cues in others. Yet, to date, there is no clear conceptual framework that predicts when decisions should evolve to be based on acoustic signals versus movement cues. Here, we first review how acoustic signals and movement cues are used for coordinating activities. We then outline how information masking, discrimination ability (Weber's Law) and encoding limitations, as well as trade-offs between these, can identify which types of collective behaviours likely rely on acoustic signals or movement cues. Specifically, our framework proposes that behaviours involving the timing of events or expression of specific actions should rely more on acoustic signals, whereas decisions involving complex choices with multiple options (e.g. direction and destination) should generally use movement cues because sounds are more vulnerable to information masking and Weber's Law effects. We then discuss potential future avenues of enquiry, including multimodal communication and collective decision-making by mixed-species animal groups. This article is part of the theme issue 'The power of sound: unravelling how acoustic communication shapes group dynamic'.
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Affiliation(s)
- Chun-Chieh Liao
- Division of Ecology and Evolution, Research School of Biology, Australian National University , Canberra, ACT , 2600, Australia
| | - Robert D Magrath
- Division of Ecology and Evolution, Research School of Biology, Australian National University , Canberra, ACT , 2600, Australia
| | - Marta B Manser
- Department of Evolutionary Biology and Environmental Studies, University of Zurich , Zürich , 8057, Switzerland
| | - Damien R Farine
- Division of Ecology and Evolution, Research School of Biology, Australian National University , Canberra, ACT , 2600, Australia
- Department of Evolutionary Biology and Environmental Studies, University of Zurich , Zürich , 8057, Switzerland
- Department of Collective Behavior, Max Planck Institute of Animal Behavior , Radolfzell , 78315, Germany
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2
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O’Connell-Rodwell CE, Berezin JL, Dharmarajan A, Ravicz ME, Hu Y, Guan X, O’Connor KN, Puria S. The impact of size on middle-ear sound transmission in elephants, the largest terrestrial mammal. PLoS One 2024; 19:e0298535. [PMID: 38598472 PMCID: PMC11006165 DOI: 10.1371/journal.pone.0298535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 01/25/2024] [Indexed: 04/12/2024] Open
Abstract
Elephants have a unique auditory system that is larger than any other terrestrial mammal. To quantify the impact of larger middle ear (ME) structures, we measured 3D ossicular motion and ME sound transmission in cadaveric temporal bones from both African and Asian elephants in response to air-conducted (AC) tonal pressure stimuli presented in the ear canal (PEC). Results were compared to similar measurements in humans. Velocities of the umbo (VU) and stapes (VST) were measured using a 3D laser Doppler vibrometer in the 7-13,000 Hz frequency range, stapes velocity serving as a measure of energy entering the cochlea-a proxy for hearing sensitivity. Below the elephant ME resonance frequency of about 300 Hz, the magnitude of VU/PEC was an order of magnitude greater than in human, and the magnitude of VST/PEC was 5x greater. Phase of VST/PEC above ME resonance indicated that the group delay in elephant was approximately double that of human, which may be related to the unexpectedly high magnitudes at high frequencies. A boost in sound transmission across the incus long process and stapes near 9 kHz was also observed. We discuss factors that contribute to differences in sound transmission between these two large mammals.
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Affiliation(s)
- Caitlin E. O’Connell-Rodwell
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Otolaryngology, Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jodie L. Berezin
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Anbuselvan Dharmarajan
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Michael E. Ravicz
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Otolaryngology, Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Yihan Hu
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Xiying Guan
- School of Medicine, Wayne State University, Detroit, Michigan, United States of America
| | - Kevin N. O’Connor
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Sunil Puria
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Otolaryngology, Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts, United States of America
- Graduate Program in Speech and Hearing and Biosciences and Technologies, Harvard Medical School, Boston, Massachusetts, United States of America
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3
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Rahman DA, Herliansyah R, Subhan B, Hutasoit D, Imron MA, Kurniawan DB, Sriyanto T, Wijayanto RD, Fikriansyah MH, Siregar AF, Santoso N. The first use of a photogrammetry drone to estimate population abundance and predict age structure of threatened Sumatran elephants. Sci Rep 2023; 13:21311. [PMID: 38042901 PMCID: PMC10693614 DOI: 10.1038/s41598-023-48635-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 11/28/2023] [Indexed: 12/04/2023] Open
Abstract
Wildlife monitoring in tropical rainforests poses additional challenges due to species often being elusive, cryptic, faintly colored, and preferring concealable, or difficult to access habitats. Unmanned aerial vehicles (UAVs) prove promising for wildlife surveys in different ecosystems in tropical forests and can be crucial in conserving inaccessible biodiverse areas and their associated species. Traditional surveys that involve infiltrating animal habitats could adversely affect the habits and behavior of elusive and cryptic species in response to human presence. Moreover, collecting data through traditional surveys to simultaneously estimate the abundance and demographic rates of communities of species is often prohibitively time-intensive and expensive. This study assesses the scope of drones to non-invasively access the Bukit Tigapuluh Landscape (BTL) in Riau-Jambi, Indonesia, and detect individual elephants of interest. A rotary-wing quadcopter with a vision-based sensor was tested to estimate the elephant population size and age structure. We developed hierarchical modeling and deep learning CNN to estimate elephant abundance and age structure. Drones successfully observed 96 distinct individuals at 8 locations out of 11 sampling areas. We obtained an estimate of the elephant population of 151 individuals (95% CI [124, 179]) within the study area and predicted more adult animals than subadults and juvenile individuals in the population. Our calculations may serve as a vital spark for innovation for future UAV survey designs in large areas with complex topographies while reducing operational effort.
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Affiliation(s)
- Dede Aulia Rahman
- Department of Forest Resources Conservation and Ecotourism, Faculty of Forestry and Environment, IPB University, Bogor, 16680, Indonesia.
- Primate Research Center, Institute of Research and Community Service, IPB University, Bogor, 16151, Indonesia.
| | - Riki Herliansyah
- School of Statistics, Kalimantan Institute of Technology, Balikpapan, 76127, Indonesia
- School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh, Edinburgh, EH9 3FD, UK
| | - Beginer Subhan
- Department of Marine Science and Technology, Faculty of Fisheries and Marine Science, IPB University, Bogor, 16680, Indonesia
| | - Donal Hutasoit
- Jambi Natural Resources Conservation Agency, Jambi, 36361, Indonesia
| | | | | | - Teguh Sriyanto
- Jambi Natural Resources Conservation Agency, Jambi, 36361, Indonesia
| | - Raden Danang Wijayanto
- Tropical Biodiversity Conservation Program, Faculty of Forestry and Environment, IPB University, Bogor, 16680, Indonesia
- Yogyakarta Natural Resources Conservation Agency, D.I. Yogyakarta, 55514, Indonesia
| | | | - Ahmad Faisal Siregar
- Tropical Biodiversity Conservation Program, Faculty of Forestry and Environment, IPB University, Bogor, 16680, Indonesia
| | - Nyoto Santoso
- Department of Forest Resources Conservation and Ecotourism, Faculty of Forestry and Environment, IPB University, Bogor, 16680, Indonesia
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Abstract
Talking to animals is a fundamental human desire. The emergence of powerful AI algorithms, and specifically Large Language Models, has driven many to suggest that we are on the verge of fulfilling this wish. A few large scientific consortia have been formed around this topic and several commercial entities even offer such services. We frame the task of communicating with animals as 'The Doctor Dolittle challenge' and identify three main obstacles on the route to doing so. First, although generative AI models can create novel animal communication samples, it is very difficult to determine their context, and we will forever be biased by our human umwelt when doing so. Second, using AI to extract context in an unsupervised manner must be validated through controlled experiments aiming to measure the animals' response. This is difficult, and moreover, AI algorithms tend to cling on to any available information and are thus prone to finding spurious correlations. And third, animal communication focuses on a restricted set of contexts, such as alarm and courtship, highly limiting our ability to communicate regarding other contexts. Nevertheless, using the tremendous power of novel AI methods to decipher and mimic animal communication is both fascinating and important. We thus define the criteria for passing the Doctor Dolittle challenge and call upon scientists to take on the mission.
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Affiliation(s)
- Yossi Yovel
- School of Zoology, Wise Faculty of Life Sciences & Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
| | - Oded Rechavi
- Department of Neurobiology, Wise Faculty of Life Sciences & Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
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5
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Beeck VC, Heilmann G, Kerscher M, Stoeger AS. Sound Visualization Demonstrates Velopharyngeal Coupling and Complex Spectral Variability in Asian Elephants. Animals (Basel) 2022; 12:2119. [PMID: 36009709 PMCID: PMC9404934 DOI: 10.3390/ani12162119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 08/02/2022] [Accepted: 08/13/2022] [Indexed: 12/05/2022] Open
Abstract
Sound production mechanisms set the parameter space available for transmitting biologically relevant information in vocal signals. Low-frequency rumbles play a crucial role in coordinating social interactions in elephants' complex fission-fusion societies. By emitting rumbles through either the oral or the three-times longer nasal vocal tract, African elephants alter their spectral shape significantly. In this study, we used an acoustic camera to visualize the sound emission of rumbles in Asian elephants, which have received far less research attention than African elephants. We recorded nine adult captive females and analyzed the spectral parameters of 203 calls, including vocal tract resonances (formants). We found that the majority of rumbles (64%) were nasally emitted, 21% orally, and 13% simultaneously through the mouth and trunk, demonstrating velopharyngeal coupling. Some of the rumbles were combined with orally emitted roars. The nasal rumbles concentrated most spectral energy in lower frequencies exhibiting two formants, whereas the oral and mixed rumbles contained higher formants, higher spectral energy concentrations and were louder. The roars were the loudest, highest and broadest in frequency. This study is the first to demonstrate velopharyngeal coupling in a non-human animal. Our findings provide a foundation for future research into the adaptive functions of the elephant acoustic variability for information coding, localizability or sound transmission, as well as vocal flexibility across species.
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Affiliation(s)
- Veronika C. Beeck
- Department of Behavioural and Cognitive Biology, University of Vienna, 1030 Vienna, Austria
| | | | | | - Angela S. Stoeger
- Department of Behavioural and Cognitive Biology, University of Vienna, 1030 Vienna, Austria
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Diurnality in the defensive behaviour of African honeybees Apis mellifera adansonii and implications for their potential efficacy in beehive fences. ORYX 2022. [DOI: 10.1017/s0030605321001721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Abstract
Across the range of African elephants Loxodonta spp., negative interactions with people are prevalent, and the impact of the resulting economic losses on farmers calls for solutions. The use of beehive fences, a mitigation method with ecological and socio-economic benefits, is gaining momentum in African savannah landscapes. We assessed the diurnal and nocturnal defensive behaviours of African honeybees Apis mellifera adansonii in response to visual and physical disturbances in the Campo–Ma'an conservation area, Cameroon. We examined six bee colonies, assessing their activity level, aggressive behaviour and ability to defend themselves when disturbed at different times of day. We found that activity levels varied between colonies and that colonies were more active during the day and inactive at night. The defensive perimeter around the hives also varied between the colonies and was generally greater during morning and evening periods. Bee colonies did not defend their hives around midday and at night. In response to a threat, bees were more likely to fly out from the hive during daytime than at night, with variation amongst colonies. Overall, as elephant intrusions occur mostly at night, beehive fences alone may not be an adequate mitigation method against crop damage caused by forest elephants Loxodonta cyclotis. We suggest combining beehive fences with other mitigation methods to improve crop protection.
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O’Connell-Rodwell CE, Sandri MN, Berezin JL, Munevar JM, Kinzley C, Wood JD, Wiśniewska M, Kilian JW. Male African Elephant (Loxodonta africana) Behavioral Responses to Estrous Call Playbacks May Inform Conservation Management Tools. Animals (Basel) 2022; 12:ani12091162. [PMID: 35565588 PMCID: PMC9102362 DOI: 10.3390/ani12091162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 04/26/2022] [Accepted: 04/27/2022] [Indexed: 02/06/2023] Open
Abstract
Simple Summary During annual periods of heightened sexual activity (musth), male African elephants expend a significant amount of energy communicating their reproductive status, as well as searching and competing for potential mates. To locate females, musth males may risk venturing outside protected areas and into landscapes shared with humans where conflict between wildlife and people can occur. Adverse interactions between elephants and people can be detrimental to human livelihoods, resulting in negative attitudes towards elephants and, in some cases, retaliatory killings. Interactions with aggressive musth males can also be life-threatening to community members who attempt to confront them. Mitigation strategies that effectively target the reproductive motivations of musth males may offer solutions as the human–elephant interface continues to expand. In this study, we build on earlier research showing that playbacks of female elephant reproductive calls, (i.e., estrous rumbles) can change the movement trajectory and behavior of male elephants in Etosha National Park, Namibia. Individuals belonging to three male groups were opportunistically subjected to playback experiments and evaluated based on their reaction intensity. Our results demonstrate that mature musth adults are more likely to change directions and approach the source of a female’s estrous call than mature, sexually-inactive adult elephants. We also show that post-dispersal young males that were not in musth also respond strongly to the stimulus. These findings support further exploration of mitigation solutions that incorporate elephant behavior, reproductive status, and context-specific vocalizations. Abstract Driven by reproductive motives, male African elephants (Loxodonta africana) in musth often expand their home ranges to locate estrous females. This extended range, coupled with heightened aggression often observed in musth males, can be particularly problematic in regions where human-modified landscapes and elephant territories increasingly overlap. Several mitigation tools have been tested to resolve a wide range of human–elephant conflicts with varying degrees of success due to geographical disparities and habituation. We present findings on the potential application of estrous call playbacks in manipulating the behavior and movement of male elephants non-invasively, particularly mature musth adults and younger post-dispersal males, in Etosha National Park. Estrous vocalizations were presented across 26 experimental trials to mature musth adults (n = 5), mature non-musth adults (n = 6), and non-musth males belonging to younger, post-dispersal age classes (n = 8), with behavioral responses scored on a gradient scale from 0–1. Both mature musth adults and younger non-musth elephants were significantly more likely to respond with the highest intensity by approaching the acoustic source compared to mature non-musth adults that avoided the call. However, younger males tested in the presence of an older, higher-ranking male tended to react with a lower intensity than those tested alone. This result likely demonstrates the influence of social hierarchy and associations on male elephant behavior. We also observed a significant increase in physiological response, measured by defecation rate, across all male groups in response to the estrous call playbacks. Our findings suggest that using estrous calls as acoustic deterrents may effectively and non-invasively aid in reducing tension at the human–elephant interface, depending on the age, social context, and reproductive status of the male elephant.
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Affiliation(s)
- Caitlin E. O’Connell-Rodwell
- Center for Conservation Biology, Stanford University, Stanford, CA 94305, USA
- Utopia Scientific, P.O. Box 221100, San Diego, CA 92192, USA; (M.N.S.); (J.L.B.)
- Harvard University Center for the Environment, Cambridge, MA 02138, USA
- Correspondence:
| | - Monica N. Sandri
- Utopia Scientific, P.O. Box 221100, San Diego, CA 92192, USA; (M.N.S.); (J.L.B.)
- Geography Graduate Group, University of California, Davis, Davis, CA 95616, USA
| | - Jodie L. Berezin
- Utopia Scientific, P.O. Box 221100, San Diego, CA 92192, USA; (M.N.S.); (J.L.B.)
- Department of Biological Sciences, Smith College, Northampton, MA 01063, USA
| | - Jaquelyn M. Munevar
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, Davis, CA 95616, USA;
| | - Colleen Kinzley
- Conservation Society of California, Oakland Zoo, Oakland, CA 94605, USA;
| | | | - Maggie Wiśniewska
- The Federated Department of Biological Sciences, New Jersey Institute of Technology, Newark, NJ 08901, USA;
| | - J. Werner Kilian
- Etosha Ecological Institute, Ministry of Environment, Forestry, and Tourism, Okaukuejo via Outjo P.O. Box 6, Namibia;
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Acknowledging the Relevance of Elephant Sensory Perception to Human–Elephant Conflict Mitigation. Animals (Basel) 2022; 12:ani12081018. [PMID: 35454264 PMCID: PMC9031250 DOI: 10.3390/ani12081018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Revised: 04/11/2022] [Accepted: 04/12/2022] [Indexed: 02/05/2023] Open
Abstract
Simple Summary Elephants have a unique sensory perspective of the world, using their complex olfactory and auditory systems to make foraging and social decisions. All three species of elephants are endangered and inhabit environments, which are being affected rapidly by human development. Anthropogenic disturbances can have significant effects on elephants’ abilities to perceive sensory information and communicate with one another, potentially further endangering their survival. Conflicts over high-quality resources also arise from the overlapping habitation of humans and elephants. While many different methods have been employed to reduce this conflict, we propose that elephants’ unique olfactory and acoustic sensory strengths be considered in future mitigation strategies to achieve coexistence. Abstract Elephants are well known for their socio-cognitive abilities and capacity for multi-modal sensory perception and communication. Their highly developed olfactory and acoustic senses provide them with a unique non-visual perspective of their physical and social worlds. The use of these complex sensory signals is important not only for communication between conspecifics, but also for decisions about foraging and navigation. These decisions have grown increasingly risky given the exponential increase in unpredictable anthropogenic change in elephants’ natural habitats. Risk taking often develops from the overlap of human and elephant habitat in Asian and African range countries, where elephants forage for food in human habitat and crop fields, leading to conflict over high-quality resources. To mitigate this conflict, a better understanding of the elephants’ sensory world and its impact on their decision-making process should be considered seriously in the development of long-term strategies for promoting coexistence between humans and elephants. In this review, we explore the elephants’ sensory systems for audition and olfaction, their multi-modal capacities for communication, and the anthropogenic changes that are affecting their behavior, as well as the need for greater consideration of elephant behavior in elephant conservation efforts.
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Fuchs E, Beeck VC, Baotic A, Stoeger AS. Acoustic structure and information content of trumpets in female Asian elephants (Elephas maximus). PLoS One 2021; 16:e0260284. [PMID: 34813615 PMCID: PMC8610244 DOI: 10.1371/journal.pone.0260284] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Accepted: 11/05/2021] [Indexed: 12/02/2022] Open
Abstract
Most studies on elephant vocal communication have focused on the low-frequency rumble, with less effort on other vocalization types such as the most characteristic elephant call, the trumpet. Yet, a better and more complete understanding of the elephant vocal system requires investigating other vocalization types and their functioning in more detail as well. We recorded adult female Asian elephants (Elephas maximus) at a private facility in Nepal and analyzed 206 trumpets from six individuals regarding their frequency, temporal and contour shape, and related acoustic parameters of the fundamental frequency. We also tested for information content regarding individuality and context. Finally, we recorded the occurrence of non-linear phenomena such as bifurcation, biphonation, subharmonics and deterministic chaos. We documented a mean fundamental frequency ± SD of 474 ± 70 Hz and a mean duration ± SD of 1.38 ± 1.46 s (Nindiv. = 6, Ncalls = 206). Our study reveals that the contour of the fundamental frequency of trumpets encodes information about individuality, but we found no evidence for trumpet subtypes in greeting versus disturbance contexts. Non-linear phenomena prevailed and varied in abundance among individuals, suggesting that irregularities in trumpets might enhance the potential for individual recognition. We propose that trumpets in adult female Asian elephants serve to convey an individual's identity as well as to signal arousal and excitement to conspecifics.
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Affiliation(s)
- Evelyn Fuchs
- Mammal Communication Lab, Department of Behavioral and Cognitive Biology, University of Vienna, Vienna, Austria
| | - Veronika C. Beeck
- Mammal Communication Lab, Department of Behavioral and Cognitive Biology, University of Vienna, Vienna, Austria
| | - Anton Baotic
- Mammal Communication Lab, Department of Behavioral and Cognitive Biology, University of Vienna, Vienna, Austria
| | - Angela S. Stoeger
- Mammal Communication Lab, Department of Behavioral and Cognitive Biology, University of Vienna, Vienna, Austria
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Does Social Complexity Drive Vocal Complexity? Insights from the Two African Elephant Species. Animals (Basel) 2021; 11:ani11113071. [PMID: 34827803 PMCID: PMC8614502 DOI: 10.3390/ani11113071] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/18/2021] [Accepted: 10/21/2021] [Indexed: 11/17/2022] Open
Abstract
Simple Summary The social complexity hypothesis (SCH) for communication predicts that species with complex social systems exhibit complex communication systems. Testing the SHC in a broad range of species can contribute to a better understanding of human evolution because a co-evolutionary runaway process between social and vocal complexity may have shaped human language. Here we compare patterns of vocal complexity between the two species of African elephants: the savanna elephant exhibiting a complex social organization and the forest elephant exhibiting a simpler social organization. We review the existing literature and present novel insights into the vocal communication system of the elusive forest elephant, along with a first direct comparison with savanna elephants. Our findings suggest that the African elephants may contradict the SCH, as well as other factors potentially shaping patterns of vocal complexity across species. A better understanding of vocal complexity in the two species of African elephants will depend on continuing advancements in remote data collection technologies to overcome the challenges of observing forest elephants in their dense rainforest habitat, as well as the availability of comparable data quantifying both structural and contextual variability in the vocal production of both species of African elephants. Abstract The social complexity hypothesis (SCH) for communication states that the range and frequency of social interactions drive the evolution of complex communication systems. Surprisingly, few studies have empirically tested the SHC for vocal communication systems. Filling this gap is important because a co-evolutionary runaway process between social and vocal complexity may have shaped the most intricate communication system, human language. We here propose the African elephant Loxodonta spec. as an excellent study system to investigate the relationships between social and vocal complexity. We review how the distinct differences in social complexity between the two species of African elephants, the forest elephant L. cyclotis and the savanna elephant L. africana, relate to repertoire size and structure, as well as complex communication skills in the two species, such as call combination or intentional formant modulation including the trunk. Our findings suggest that Loxodonta may contradict the SCH, as well as other factors put forth to explain patterns of vocal complexity across species. We propose that life history traits, a factor that has gained little attention as a driver of vocal complexity, and the extensive parental care associated with a uniquely low and slow reproductive rate, may have led to the emergence of pronounced vocal complexity in the forest elephant despite their less complex social system compared to the savanna elephant. Conclusions must be drawn cautiously, however. A better understanding of vocal complexity in the genus Loxodonta will depend on continuing advancements in remote data collection technologies to overcome the challenges of observing forest elephants in their dense rainforest habitat, as well as the availability of directly comparable data and methods, quantifying both structural and contextual variability in the production of rumbles and other vocalizations in both species of African elephants.
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11
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Crunchant AS, Stewart FA, Piel AK. Vocal communication in wild chimpanzees: a call rate study. PeerJ 2021; 9:e12326. [PMID: 34721995 PMCID: PMC8532989 DOI: 10.7717/peerj.12326] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 09/27/2021] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Patterns of vocal communication have implications for species conservation: a change in calling behaviour can, for instance, reflect a disturbed habitat. More importantly, call rate is a parameter that allows conservation planners to convert call density into animal density, when detecting calls with a passive acoustic monitoring system (PAM). METHODS We investigated chimpanzee (Pan troglodytes schweinfurthii) call rate during the late dry season in the Issa Valley, western Tanzania by conducting focal follows. We examined the socio-ecological factors that influence call production rate of savanna woodland chimpanzees. RESULTS We found that sex, proportion of time spent in a vegetation type, proportion of time spent travelling, time of the day, party size and swollen parous female presence had a significant effect on the call rate. Call rate differed among the different demographic classes with subadult and adult males vocalising twice as often as the subadult and adult females and three times as often as the juveniles. APPLICATIONS The use of PAM and recent statistical developments to estimate animal density is promising but relies on our knowing individual call rate, often not available for many species. With the improvement in automatic call detection, we anticipate that PAM will increasingly be broadly applied to primates but also across taxa, for conservation.
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Affiliation(s)
- Anne-Sophie Crunchant
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, United Kingdom
| | - Fiona A. Stewart
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, United Kingdom
- Department of Anthropology, University College London, London, United Kingdom
| | - Alex K. Piel
- Department of Anthropology, University College London, London, United Kingdom
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12
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Hartmann WL, Fishlock V, Leslie A. First guidelines and suggested best protocol for surveying African elephants (Loxodonta africana) using a drone. KOEDOE: AFRICAN PROTECTED AREA CONSERVATION AND SCIENCE 2021. [DOI: 10.4102/koedoe.v63i1.1687] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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13
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Stoeger AS, Baotic A, Heilmann G. Vocal Creativity in Elephant Sound Production. BIOLOGY 2021; 10:750. [PMID: 34439982 PMCID: PMC8389636 DOI: 10.3390/biology10080750] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 08/01/2021] [Accepted: 08/02/2021] [Indexed: 11/16/2022]
Abstract
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.
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Affiliation(s)
- Angela S. Stoeger
- Mammal Communication Lab, Department of Behavioral and Cognitive Biology, University of Vienna, 1030 Vienna, Austria;
| | - Anton Baotic
- Mammal Communication Lab, Department of Behavioral and Cognitive Biology, University of Vienna, 1030 Vienna, Austria;
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Mortimer B, Walker JA, Lolchuragi DS, Reinwald M, Daballen D. Noise matters: elephants show risk-avoidance behaviour in response to human-generated seismic cues. Proc Biol Sci 2021; 288:20210774. [PMID: 34187196 PMCID: PMC8242925 DOI: 10.1098/rspb.2021.0774] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
African elephants (Loxodonta africana) use many sensory modes to gather information about their environment, including the detection of seismic, or ground-based, vibrations. Seismic information is known to include elephant-generated signals, but also potentially encompasses biotic cues that are commonly referred to as ‘noise’. To investigate seismic information transfer in elephants beyond communication, here we tested the hypothesis that wild elephants detect and discriminate between seismic vibrations that differ in their noise types, whether elephant- or human-generated. We played three types of seismic vibrations to elephants: seismic recordings of elephants (elephant-generated), white noise (human-generated) and a combined track (elephant- and human-generated). We found evidence of both detection of seismic noise and discrimination between the two treatments containing human-generated noise. In particular, we found evidence of retreat behaviour, where seismic tracks with human-generated noise caused elephants to move further away from the trial location. We conclude that seismic noise are cues that contain biologically relevant information for elephants that they can associate with risk. This expands our understanding of how elephants use seismic information, with implications for elephant sensory ecology and conservation management.
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Affiliation(s)
- Beth Mortimer
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK
| | - James A Walker
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK
| | | | | | - David Daballen
- Save the Elephants, Marula Manor, Karen, Nairobi 00200, Kenya
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Beeck VC, Heilmann G, Kerscher M, Stoeger AS. A novel theory of Asian elephant high-frequency squeak production. BMC Biol 2021; 19:121. [PMID: 34134675 PMCID: PMC8210382 DOI: 10.1186/s12915-021-01026-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 04/14/2021] [Indexed: 11/10/2022] Open
Abstract
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.
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Affiliation(s)
- Veronika C Beeck
- Department of Behavioural and Cognitive Biology, Mammal Communication Lab, University of Vienna, Vienna, Austria.
| | | | | | - Angela S Stoeger
- Department of Behavioural and Cognitive Biology, Mammal Communication Lab, University of Vienna, Vienna, Austria.
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16
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Oduor S, Brown J, Macharia GM, Boisseau N, Murray S, Obade P. Differing physiological and behavioral responses to anthropogenic factors between resident and non-resident African elephants at Mpala Ranch, Laikipia County, Kenya. PeerJ 2020; 8:e10010. [PMID: 33062433 PMCID: PMC7528812 DOI: 10.7717/peerj.10010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 08/31/2020] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Heterogeneous landscapes like those of Laikipia County, Kenya consist of a mosaic of land-use types, which may exert differential physiological effects on elephants that occupy and traverse them. Understanding behavioral and physiological states of wild African elephants in response to the challenges of living in human-dominated landscapes is therefore important for conservation managers to evaluate risks imposed by elephants to humans and vice versa. Several conservation physiology tools have been developed to assess how animals respond to both natural and anthropogenic changes, and determine biological impacts. This study investigated how migratory and avoidance behavioral to vehicle presence, and vegetation quality affected fecal glucocorticoid (GC) metabolite (FGM) concentrations in African elephants at Mpala Ranch, Laikipia County, Kenya. METHODS The study compared adrenal glucocorticoid activity of resident elephants that live within Mpala (n = 57) and non-resident elephants whose space use patterns overlap several ranches (n = 99) in Laikipia County, Kenya. Fecal samples were collected for a 4-month period between April and August for analysis of FGM concentrations. Behavioral reactions to research vehicles and body condition also were assessed. Satellite images from Terra Moderate Resolution Imaging (MODIS MOD13Q1) were downloaded and processed using Google Earth Engine to calculate a Normalized Difference Vegetation Index (NDVI) as a measure of vegetation quality. RESULTS As expected, there was a positive correlation between avoidance behavior to vehicle presence and FGM concentrations in both resident and non-resident elephants, whereas there was an inverse relationship between FGM concentrations and NDVI values. Our study also found a positive influence of age on the FGM concentrations, but there were no relationships between FGM and sex, social group type, herd size, and body condition. However, contrary to our expectations, resident elephants had higher FGM concentrations than non-residents. DISCUSSION Findings reveal elephants with stronger avoidance responses to research vehicles and resident elephants with relatively smaller home ranges exhibited higher FGM concentrations within the Mpala Ranch, Kenya and surrounding areas. Higher vegetative quality within the ranges occupied by non-resident elephants in Laikipia may be one reason for lower FGM, and an indication that the non-residents are tracking better forage quality to improve energy balance and reduce overall GC output. Additionally, our study found a positive influence of age, but no other demographic variables on FGM concentrations. Finally, adrenal glucocorticoid activity was inversely related to vegetative quality. Our findings can help conservation managers better understand how behavior and environment influences the physiological states of African elephants, and how management intervention might mitigate negative human-elephant interactions.
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Affiliation(s)
- Sandy Oduor
- Research, Mpala Research Centre, Nanyuki, Laikipia, Kenya
| | - Janine Brown
- Center for Species Survival, Smithsonian Conservation Biology Institute, Front Royal, VA, USA
| | - Geoffrey M. Macharia
- Department of Environmental Science, Kenyatta University, Nairobi, Nairobi, Kenya
| | - Nicole Boisseau
- Endocrine Lab, Smithsonian Conservation Biology Institute, Front Royal, VA, USA
| | - Suzan Murray
- Global Health Program, Smithsonian Conservation Biology Institute, Washington, DC, USA
| | - Paul Obade
- Department of Environmental Science, Kenyatta University, Nairobi, Nairobi, Kenya
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Water A, King LE, Arkajak R, Arkajak J, Doormaal N, Ceccarelli V, Sluiter L, Doornwaard SM, Praet V, Owen D, Matteson K. Beehive fences as a sustainable local solution to human‐elephant conflict in Thailand. CONSERVATION SCIENCE AND PRACTICE 2020. [DOI: 10.1111/csp2.260] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Affiliation(s)
- Antoinette Water
- Department of Biology Miami University Oxford Ohio USA
- Bring The Elephant Home Vlaardingen The Netherlands
| | - Lucy E. King
- Department of Zoology University of Oxford Oxford UK
- Save the Elephants Nairobi Kenya
| | - Rachaya Arkajak
- Phuluang Wildlife Research Station, Department of National Parks Wildlife and Plant Conservation Bangkok Thailand
| | - Jirachai Arkajak
- Phuluang Wildlife Research Station, Department of National Parks Wildlife and Plant Conservation Bangkok Thailand
| | - Nick Doormaal
- Future For Nature Academy Wildlife Ecology and Conservation Group Wageningen the Netherlands
| | | | | | | | - Vera Praet
- Bring The Elephant Home Vlaardingen The Netherlands
| | - David Owen
- Department of Biology Miami University Oxford Ohio USA
- Bring The Elephant Home Vlaardingen The Netherlands
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19
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Wright MG, Spencer C, Cook RM, Henley MD, North W, Mafra-Neto A. African bush elephants respond to a honeybee alarm pheromone blend. Curr Biol 2019; 28:R778-R780. [PMID: 30040934 DOI: 10.1016/j.cub.2018.06.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
We here report the responses of African bush elephants (Loxodonta africana) to a crude approximation of the honeybee alarm pheromone blend. We show that the elephants had an avoidance response to the semiochemical blend. The use of honeybee alarm pheromones to manage elephant movements in a non-invasive manner, using natural cues to which elephants may have an evolved response, holds potential for development of new options for an integrated system for elephant movement management and protection.
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Affiliation(s)
- Mark G Wright
- Department of Plant and Environmental Protection Sciences, University of Hawaii at Manoa, 3050 Maile Way, Honolulu, HI 96822, USA.
| | | | - Robin M Cook
- Elephants Alive, P.O. Box 960, Hoedspruit 1380, South Africa
| | - Michelle D Henley
- Elephants Alive, P.O. Box 960, Hoedspruit 1380, South Africa; Applied Behavioural Ecology and Ecosystem Research Unit, School of Environmental Sciences, University of South Africa, Private Bag X5, Florida 1710, South Africa
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20
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Hedwig D, Verahrami AK, Wrege PH. Acoustic structure of forest elephant rumbles: a test of the ambiguity reduction hypothesis. Anim Cogn 2019; 22:1115-1128. [PMID: 31535246 DOI: 10.1007/s10071-019-01304-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 08/13/2019] [Accepted: 08/31/2019] [Indexed: 11/27/2022]
Abstract
Quantitative assessments of the structure of vocalizations are a fundamental prerequisite to understand a species' vocal communication system and, more broadly, the selective pressures shaping vocal repertoires. For example, to reduce ambiguity in signal interpretation in the absence of auxiliary visual cues, species in densely vegetated habitats should exhibit more discrete vocal signals than species in open habitats. To test this "ambiguity reduction hypothesis", we conducted the first quantitative assessment of the rumble vocalizations of the forest elephant. Based on 686 forest elephant rumbles recorded with autonomous acoustic recording units at four sites across Central Africa, we used model-based cluster analyses paired with subsequent evaluation of cluster-discreteness and discriminant function analyses to quantify the structure of rumbles based on 23 source- and filter-related acoustic parameters. Model-based cluster analyses suggest that rumbles can be classified into five to eight types. Similar to previous findings in savannah elephants and contrary to the ambiguity reduction hypothesis, average silhouette coefficients below 0.34 indicated that these rumble types were highly intergraded. However, discriminant function analyses predicted rumble types with at least 75% accuracy whereby the location of the minimum fundamental frequency, middle slope and peak frequency contributed most to separation between types. In line with an increasing number of studies highlighting that a distinction between discrete and graded repertoires may have little biological significance, we propose that ambiguity reduction may take place through the evolution of perceptual and cognitive mechanisms, rather than acting on vocal production.
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Affiliation(s)
- Daniela Hedwig
- Elephant Listening Project, Center for Conservation Bioacoustics, Cornell Lab of Ornithology, Cornell University, Ithaca, USA.
| | - Anahita K Verahrami
- Elephant Listening Project, Center for Conservation Bioacoustics, Cornell Lab of Ornithology, Cornell University, Ithaca, USA
| | - Peter H Wrege
- Elephant Listening Project, Center for Conservation Bioacoustics, Cornell Lab of Ornithology, Cornell University, Ithaca, USA
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21
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Baotic A, Garcia M, Boeckle M, Stoeger A. Field Propagation Experiments of Male African Savanna Elephant Rumbles: A Focus on the Transmission of Formant Frequencies. Animals (Basel) 2018; 8:E167. [PMID: 30274350 PMCID: PMC6210294 DOI: 10.3390/ani8100167] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 09/23/2018] [Accepted: 09/25/2018] [Indexed: 11/16/2022] Open
Abstract
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.
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Affiliation(s)
- Anton Baotic
- Mammal Communication Lab, Department of Cognitive Biology, University of Vienna, Vienna 1090, Austria.
| | - Maxime Garcia
- Mammal Communication Lab, Department of Cognitive Biology, University of Vienna, Vienna 1090, Austria.
- ENES Lab, Neuro-PSI, CNRS UMR 9197, University of Lyon/Saint Etienne, 42023 Saint Etienne, France.
| | - Markus Boeckle
- Department of Psychology, University of Cambridge, Cambridge CB2 3EB, UK.
- Department of Psychotherapy, Bertha von Suttner University, St. Poelten 3100, Austria.
| | - Angela Stoeger
- Mammal Communication Lab, Department of Cognitive Biology, University of Vienna, Vienna 1090, Austria.
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Not so far: attenuation of low-frequency vocalizations in a rainforest environment suggests limited acoustic mediation of social interaction in African forest elephants. Behav Ecol Sociobiol 2018. [DOI: 10.1007/s00265-018-2451-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Limacher-Burrell A, Bhagwandin A, Maseko BC, Manger PR. Nuclear organization of the African elephant (Loxodonta africana) amygdaloid complex: an unusual mammalian amygdala. Brain Struct Funct 2017; 223:1191-1216. [PMID: 29098403 DOI: 10.1007/s00429-017-1555-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 10/24/2017] [Indexed: 11/25/2022]
Abstract
Here we describe the nuclear organization of the African elephant amygdaloid complex using Nissl, myelin, and a range of immunohistochemical stains. The African elephant is thought to exhibit many affect-laden and social-empathic behaviours; however, to date the amygdaloid complex, which is the generator of emotional states of the brain is yet to be fully explored in the elephants. For the most part, the amygdaloid complex of the African elephant is similar to that observed in other mammals in terms of the presence of nuclei and their topological relationships; however, we did observe several specific differences in amygdaloid organization. The elephant amygdala has undergone rotation in both the coronal and sagittal planes, seemingly associated with the expansion of the temporal lobe. Numerous scalloped cell clusters, termed glomeruli, forming the intermediate nuclei of the basal, accessory basal and central nuclear groups, were occupied by structures immunopositive to doublecortin. The nuclei typically associated with the accessory olfactory system (posterior cortical nucleus and medial nuclear complex) were absent from the elephant amygdala. The anterior cortical nucleus is very large and appears to be comprised of two subdivisions. The lateral nuclear complex is expanded and has two novel subdivisions. The amygdalohippocampal area appears relatively enlarged. The numerous shared and derived characters make the elephant amygdaloid complex very unusual and unique amongst mammals, but the derived characters appear to relate to observed elephant affect-laden behaviours.
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Affiliation(s)
- Aude'Marie Limacher-Burrell
- School of Anatomical Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg, 2193, South Africa
| | - Adhil Bhagwandin
- School of Anatomical Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg, 2193, South Africa
| | - Busisiwe C Maseko
- School of Anatomical Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg, 2193, South Africa
| | - Paul R Manger
- School of Anatomical Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg, 2193, South Africa.
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High tech cognitive and acoustic enrichment for captive elephants. J Neurosci Methods 2017; 300:173-183. [PMID: 28951175 DOI: 10.1016/j.jneumeth.2017.09.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 09/15/2017] [Accepted: 09/15/2017] [Indexed: 11/24/2022]
Abstract
This paper investigates the potential for using technology to support the development of sensory and cognitive enrichment activities for captive elephants. It explores the usefulness of applying conceptual frameworks from interaction design and game design to the problem of developing species-specific smart toys that promote natural behaviours and provide stimulation. We adopted a Research through Design approach, and describe how scientific inquiry supported our design process, while the creation of artefacts guided our investigations into possible future solutions. Our fieldwork resulted in the development of an interactive prototype of an acoustic toy that elephants are able to control using interface elements constructed from a range of natural materials.
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25
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Fritz H. Long-term field studies of elephants: understanding the ecology and conservation of a long-lived ecosystem engineer. J Mammal 2017. [DOI: 10.1093/jmammal/gyx023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Baotic A, Stoeger AS. Sexual dimorphism in African elephant social rumbles. PLoS One 2017; 12:e0177411. [PMID: 28489908 PMCID: PMC5425207 DOI: 10.1371/journal.pone.0177411] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 04/26/2017] [Indexed: 11/21/2022] Open
Abstract
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.
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Affiliation(s)
- Anton Baotic
- Mammal Communication Lab, Department of Cognitive Biology, University of Vienna, Vienna, Austria
| | - Angela S. Stoeger
- Mammal Communication Lab, Department of Cognitive Biology, University of Vienna, Vienna, Austria
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Stoeger AS, Baotic A. Male African elephants discriminate and prefer vocalizations of unfamiliar females. Sci Rep 2017; 7:46414. [PMID: 28422091 PMCID: PMC5395942 DOI: 10.1038/srep46414] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 03/17/2017] [Indexed: 11/15/2022] Open
Abstract
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.
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Affiliation(s)
- Angela S. Stoeger
- Mammal Communication Lab, Department of Cognitive Biology, Althanstrasse 14, 1090, University of Vienna, Austria
| | - Anton Baotic
- Mammal Communication Lab, Department of Cognitive Biology, Althanstrasse 14, 1090, University of Vienna, Austria
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28
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Unmanned aerial vehicles mitigate human–elephant conflict on the borders of Tanzanian Parks: a case study. ORYX 2016. [DOI: 10.1017/s0030605316000946] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
AbstractProtected areas across the range of the African savannah elephant Loxodonta africana are increasingly being surrounded and isolated by agriculture and human settlements. Conflicts between people and crop-raiding elephants regularly lead to direct reprisals and diminish community support for conservation. We report on field trials in northern Tanzania that employed a new, humane way for wildlife managers to move elephants away from conflict zones, from distances of > 100 m, thereby enhancing the safety of wildlife managers, farmers and elephants. We deployed 10 unmanned aerial vehicles (drones) piloted by five trained teams of wildlife managers in the Tarangire–Manyara and Serengeti ecosystems. Game Scouts deployed the drones opportunistically during crop-raiding events at the peak of the maize ripening period in 2015 and 2016. In 100% of trials (n = 51) elephants responded to the presence of a drone by departing rapidly from crop fields (n = 38) and settlements (n = 13). The cost of five teams responsible for 617 km2 in Tarangire–Manyara was estimated to be USD 15,520 for 1 year, and all drones remained operational for the duration of the study. The initial success of this tool warrants further testing of the utility of small unmanned aerial vehicles as part of the toolbox for wildlife managers and communities dealing with high levels of conflict with wildlife.
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Stoeger AS, Baotic A. Information content and acoustic structure of male African elephant social rumbles. Sci Rep 2016; 6:27585. [PMID: 27273586 PMCID: PMC4897791 DOI: 10.1038/srep27585] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 05/17/2016] [Indexed: 11/14/2022] Open
Abstract
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.
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Affiliation(s)
- Angela S. Stoeger
- Mammal Communication Lab, Department of Cognitive Biology, University of Vienna, Vienna, 1090, Austria
| | - Anton Baotic
- Mammal Communication Lab, Department of Cognitive Biology, University of Vienna, Vienna, 1090, Austria
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30
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How Bees Deter Elephants: Beehive Trials with Forest Elephants (Loxodonta africana cyclotis) in Gabon. PLoS One 2016; 11:e0155690. [PMID: 27196059 PMCID: PMC4873247 DOI: 10.1371/journal.pone.0155690] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 05/03/2016] [Indexed: 11/19/2022] Open
Abstract
In Gabon, like elsewhere in Africa, crops are often sources of conflict between humans and wildlife. Wildlife damage to crops can drastically reduce income, amplifying poverty and creating a negative perception of wild animal conservation among rural people. In this context, crop-raiding animals like elephants quickly become “problem animals”. To deter elephants from raiding crops beehives have been successfully employed in East Africa; however, this method has not yet been tested in Central Africa. We experimentally examined whether the presence of Apis mellifera adansonii, the African honey bee species present in Central Africa, deters forest elephants (Loxodonta Africana cyclotis) from feeding on fruit trees. We show for the first time that the effectiveness of beehives as deterrents of elephants is related to bee activity. Empty hives and those housing colonies of low bee activity do not deter elephants all the time; but beehives with high bee activity do. Although elephant disturbance of hives does not impede honey production, there is a tradeoff between deterrence and the quantity of honey produced. To best achieve the dual goals of deterring elephants and producing honey colonies must maintain an optimum activity level of 40 to 60 bee movements per minute. Thus, beehives colonized by Apis mellifera adansonii bees can be effective elephant deterrents, but people must actively manage hives to maintain bee colonies at the optimum activity level.
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Infrasonic and Seismic Communication in the Vertebrates with Special Emphasis on the Afrotheria: An Update and Future Directions. VERTEBRATE SOUND PRODUCTION AND ACOUSTIC COMMUNICATION 2016. [DOI: 10.1007/978-3-319-27721-9_7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Zeppelzauer M, Stoeger AS. Establishing the fundamentals for an elephant early warning and monitoring system. BMC Res Notes 2015; 8:409. [PMID: 26338528 PMCID: PMC4558827 DOI: 10.1186/s13104-015-1370-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 08/18/2015] [Indexed: 11/25/2022] Open
Abstract
Background 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. Findings 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. Discussion 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.
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Affiliation(s)
- Matthias Zeppelzauer
- Media Computing Group, St. Pölten University of Applied Sciences, Matthias-Corvinus Strasse 15, 3100, St. Pölten, Austria.
| | - Angela S Stoeger
- Department of Cognitive Biology, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
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Ein-Dor T. Facing danger: how do people behave in times of need? The case of adult attachment styles. Front Psychol 2014; 5:1452. [PMID: 25540635 PMCID: PMC4261697 DOI: 10.3389/fpsyg.2014.01452] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 11/27/2014] [Indexed: 11/13/2022] Open
Abstract
Bowlby’s (1982) attachment theory has generated an enormous body of research and conceptual elaborations. Although attachment theory and research propose that attachment security provides a person with many adaptive advantages, during all phases of the life cycle, numerous studies indicate that almost half of the human species can be classified as insecurely attached or insecure with respect to attachment. It seems odd that evolution left humans in this vulnerable position, unless there are some advantages to individuals or groups, under at least some conditions, of anxious and avoidant attachment styles. I argue that a social group containing members with different attachment patterns may be more conducive to survival than a homogeneous group of securely attached individuals because each attachment disposition has specific adaptive advantages that promote the survival of the individual and people around him or her when facing threats and perils. In making this argument, I extend the scope of attachment theory and research by considering a broader range of adaptive functions of insecure attachment strategies, and present data to support my argument.
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Affiliation(s)
- Tsachi Ein-Dor
- Interdisciplinary Center Herzliya, School of Psychology Herzliya, Israel
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Stoeger AS, Manger P. Vocal learning in elephants: neural bases and adaptive context. Curr Opin Neurobiol 2014; 28:101-7. [PMID: 25062469 PMCID: PMC4181794 DOI: 10.1016/j.conb.2014.07.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 06/28/2014] [Accepted: 07/01/2014] [Indexed: 10/28/2022]
Abstract
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.
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Affiliation(s)
- Angela S Stoeger
- Department of Cognitive Biology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria.
| | - Paul Manger
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
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