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Caldwell MS, Britt KA, Mischke LC, Collins HI. Beyond sound: Bimodal acoustic calls used in mate-choice and aggression by red-eyed treefrogs. J Exp Biol 2022; 225:276426. [PMID: 35938394 DOI: 10.1242/jeb.244460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Accepted: 07/27/2022] [Indexed: 11/20/2022]
Abstract
Airborne sound signals function as key mediators of mate-choice, aggression, and other social interactions in a wide range of vertebrate and invertebrate animals. Calling animals produce more than sound, however. When displaying on or near a solid substrate, such as vegetation or soil, they also unavoidably excite substrate vibrations due to the physics of sound production and of acoustic propagation, and these vibrations can propagate to receivers. Despite their near ubiquity, these vibrational signal components have received very little research attention, and in vertebrates it is completely unknown whether they are relevant to mate-choice, an important driver of evolutionary divergence. Here we show that female red-eyed treefrogs are more than twice as likely to choose a male mating call when airborne sound is paired with its corresponding substrate vibrations. Furthermore, males of the same species are more aggressive towards and display a greater range of aggressive behaviors in response to bimodal (sound and vibration) versus unimodal (sound or vibration alone) calls. In aggressive contexts, at least, air- and substrate-borne signal components function non-redundantly. These results are a clear demonstration that vibrations produced by a calling animal can function together with airborne sound to markedly enhance the function of a signal. If this phenomenon proves widespread, this finding has the potential to substantially influence our understanding of the function and evolution of acoustic signals.
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Affiliation(s)
- Michael S Caldwell
- Gettysburg College, Department of Biology, 300 N. Washington St., Gettysburg, PA 17325, USA.,Smithsonian Tropical Research Institute, Apartado 0843-03092, Panamá, República de Panamá, USA
| | - Kayla A Britt
- Gettysburg College, Department of Biology, 300 N. Washington St., Gettysburg, PA 17325, USA
| | - Lilliana C Mischke
- Gettysburg College, Department of Biology, 300 N. Washington St., Gettysburg, PA 17325, USA
| | - Hannah I Collins
- Gettysburg College, Department of Biology, 300 N. Washington St., Gettysburg, PA 17325, USA.,University of Connecticut Avery Point, Department of Marine Sciences, 1080 Shennecossett Rd., Groton, CT 06340, USA
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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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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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4
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Reinwald M, Moseley B, Szenicer A, Nissen-Meyer T, Oduor S, Vollrath F, Markham A, Mortimer B. Seismic localization of elephant rumbles as a monitoring approach. J R Soc Interface 2021; 18:20210264. [PMID: 34255988 PMCID: PMC8277467 DOI: 10.1098/rsif.2021.0264] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 06/23/2021] [Indexed: 11/12/2022] Open
Abstract
African elephants (Loxodonta africana) are sentient and intelligent animals that use a variety of vocalizations to greet, warn or communicate with each other. Their low-frequency rumbles propagate through the air as well as through the ground and the physical properties of both media cause differences in frequency filtering and propagation distances of the respective wave. However, it is not well understood how each mode contributes to the animals' abilities to detect these rumbles and extract behavioural or spatial information. In this study, we recorded seismic and co-generated acoustic rumbles in Kenya and compared their potential use to localize the vocalizing animal using the same multi-lateration algorithms. For our experimental set-up, seismic localization has higher accuracy than acoustic, and bimodal localization does not improve results. We conclude that seismic rumbles can be used to remotely monitor and even decipher elephant social interactions, presenting us with a tool for far-reaching, non-intrusive and surprisingly informative wildlife monitoring.
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Affiliation(s)
| | - Ben Moseley
- Department of Computer Science, University of Oxford, Oxford, UK
| | | | | | | | - Fritz Vollrath
- Department of Zoology, University of Oxford, Oxford, UK
- Save the Elephants, Marula Manor, Karen, Nairobi, Kenya
| | - Andrew Markham
- Department of Computer Science, University of Oxford, Oxford, UK
| | - Beth Mortimer
- Department of Zoology, University of Oxford, Oxford, UK
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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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Lamb OD, Shore MJ, Lees JM, Lee SJ, Hensman SM. Assessing Raspberry Shake and Boom Sensors for Recording African Elephant Acoustic Vocalizations. FRONTIERS IN CONSERVATION SCIENCE 2021. [DOI: 10.3389/fcosc.2020.630967] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Acoustic sensors are increasingly being used in ecological and conservation research, but the choice of sensor can be fraught with trade-offs. In this work we assess the performance of the Raspberry Shake and Boom (RS&B) sensor package for detecting and monitoring African elephants (Loxodonta africana). This is the first documented test of this particular unit for recording animal behavior; the unit was originally designed for detecting tectonic earthquakes and low frequency (<50 Hz) atmospheric acoustics. During a four day deployment in South Africa we tested five RS&B units for recording acoustic and seismic vocalizations generated by a group of African elephants. Our results highlight a varied degree of success in detecting the signals of interest. The acoustic microphone recorded fundamental frequencies of low-frequency (<50 Hz) harmonic vocalizations that were not clearly recorded by more sensitive instruments, but was not able to record higher frequency harmonics due to the low sampling rate (100 Hz). The geophone was not able to consistently record clear seismic waves generated by vocalizations but was able to record higher harmonics. In addition, seismic signals were detected from footsteps of elephants at <50 m distance. We conclude that the RS&B unit currently shows limited potential as a monitoring tool for African elephants and we propose several future directions and deployment strategies to improve the sensitivity of the sensor package.
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Abstract
Adipose tissue depots can exist in close association with other organs, where they assume diverse, often non-traditional functions. In stem cell-rich skin, bone marrow, and mammary glands, adipocytes signal to and modulate organ regeneration and remodeling. Skin adipocytes and their progenitors signal to hair follicles, promoting epithelial stem cell quiescence and activation, respectively. Hair follicles signal back to adipocyte progenitors, inducing their expansion and regeneration, as in skin scars. In mammary glands and heart, adipocytes supply lipids to neighboring cells for nutritional and metabolic functions, respectively. Adipose depots adjacent to skeletal structures function to absorb mechanical shock. Adipose tissue near the surface of skin and intestine senses and responds to bacterial invasion, contributing to the body's innate immune barrier. As the recognition of diverse adipose depot functions increases, novel therapeutic approaches centered on tissue-specific adipocytes are likely to emerge for a range of cancers and regenerative, infectious, and autoimmune disorders.
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Affiliation(s)
- Rachel K Zwick
- Department of Molecular, Cellular, and Developmental Biology, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA
| | - Christian F Guerrero-Juarez
- Department of Developmental and Cell Biology, University of California, Irvine, 845 Health Sciences Road, Irvine, CA 92697, USA; Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92697, USA; Center for Complex Biological Systems, University of California, Irvine, Irvine, CA 92697, USA
| | - Valerie Horsley
- Department of Molecular, Cellular, and Developmental Biology, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA; Department of Dermatology, Yale School of Medicine, Yale University, New Haven, CT 06520, USA.
| | - Maksim V Plikus
- Department of Developmental and Cell Biology, University of California, Irvine, 845 Health Sciences Road, Irvine, CA 92697, USA; Sue and Bill Gross Stem Cell Research Center, University of California, Irvine, Irvine, CA 92697, USA; Center for Complex Biological Systems, University of California, Irvine, Irvine, CA 92697, USA.
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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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9
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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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10
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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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11
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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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12
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Viljoen JJ, Ganswindt A, Reynecke C, Stoeger AS, Langbauer WR. Vocal stress associated with a translocation of a family herd of African elephants (Loxodonta africana) in the Kruger National Park, South Africa. BIOACOUSTICS 2014. [DOI: 10.1080/09524622.2014.906320] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Jozua Jakobus Viljoen
- Department of Nature Conservation, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa
| | - Andre Ganswindt
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20 Hatfield, Pretoria 0028, South Africa
| | - Christopher Reynecke
- Department of Nature Conservation, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa
| | - Angela S. Stoeger
- Department of Cognitive Biology, University of Vienna, Althanstrasse 14, 1090Vienna, Austria
| | - William Richard Langbauer
- Department of Science & Conservation, Pittsburgh Zoo & PPG Aquarium, One Wild Place, Pittsburgh, PA15206, USA
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13
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Cocroft RB, Gogala M, Hill PSM, Wessel A. Fostering Research Progress in a Rapidly Growing Field. ANIMAL SIGNALS AND COMMUNICATION 2014. [DOI: 10.1007/978-3-662-43607-3_1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Maseko BC, Patzke N, Fuxe K, Manger PR. Architectural Organization of the African Elephant Diencephalon and Brainstem. BRAIN, BEHAVIOR AND EVOLUTION 2013; 82:83-128. [DOI: 10.1159/000352004] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 05/03/2013] [Indexed: 11/19/2022]
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O'Connell-Rodwell CE, Wood JD, Wyman M, Redfield S, Puria S, Hart LA. Antiphonal vocal bouts associated with departures in free-ranging African elephant family groups (Loxodonta africana). BIOACOUSTICS 2012. [DOI: 10.1080/09524622.2012.686166] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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16
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Wrege PH, Rowland ED, Thompson BG, Batruch N. Use of acoustic tools to reveal otherwise cryptic responses of forest elephants to oil exploration. CONSERVATION BIOLOGY : THE JOURNAL OF THE SOCIETY FOR CONSERVATION BIOLOGY 2010; 24:1578-1585. [PMID: 20666800 DOI: 10.1111/j.1523-1739.2010.01559.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Most evaluations of the effects of human activities on wild animals have focused on estimating changes in abundance and distribution of threatened species; however, ecosystem disturbances also affect aspects of animal behavior such as short-term movement, activity budgets, and reproduction. It may take a long time for changes in behavior to manifest as changes in abundance or distribution. Therefore, it is important to have methods with which to detect short-term behavioral responses to human activity. We used continuous acoustic and seismic monitoring to evaluate the short-term effects of seismic prospecting for oil on forest elephants (Loxodonta cyclotis) in Gabon, Central Africa. We monitored changes in elephant abundance and activity as a function of the frequency and intensity of acoustic and seismic signals from dynamite detonation and human activity. Elephants did not flee the area being explored; the relative number of elephants increased in a seasonal pattern typical of elsewhere in the ecosystem. In the exploration area, however, they became more nocturnal. Neither the intensity nor the frequency of dynamite blasts affected the frequency of calling or the daily pattern of elephant activity. Nevertheless, the shift of activity to nocturnal hours became more pronounced as human activity neared each monitored area of forest. This change in activity pattern and its likely causes would not have been detected through standard monitoring methods, which are not sensitive to behavioral changes over short time scales (e.g., dung transects, point counts) or cover a limited area (e.g., camera traps). Simultaneous acoustic monitoring of animal communication, human, and environmental sounds allows the documentation of short-term behavioral changes in response to human disturbance.
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Affiliation(s)
- Peter H Wrege
- The Elephant Listening Project, Bioacoustics Research Program, Cornell Lab of Ornithology, Ithaca, NY 14850-1923, USA.
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Abstract
Research on vocal communication in African elephants has increased in recent years, both in the wild and in captivity, providing an opportunity to present a comprehensive review of research related to their vocal behavior. Current data indicate that the vocal repertoire consists of perhaps nine acoustically distinct call types, "rumbles" being the most common and acoustically variable. Large vocal production anatomy is responsible for the low-frequency nature of rumbles, with fundamental frequencies in the infrasonic range. Additionally, resonant frequencies of rumbles implicate the trunk in addition to the oral cavity in shaping the acoustic structure of rumbles. Long-distance communication is thought possible because low-frequency sounds propagate more faithfully than high-frequency sounds, and elephants respond to rumbles at distances of up to 2.5 km. Elephant ear anatomy appears designed for detecting low frequencies, and experiments demonstrate that elephants can detect infrasonic tones and discriminate small frequency differences. Two vocal communication functions in the African elephant now have reasonable empirical support. First, closely bonded but spatially separated females engage in rumble exchanges, or "contact calls," that function to coordinate movement or reunite animals. Second, both males and females produce "mate attraction" rumbles that may advertise reproductive states to the opposite sex. Additionally, there is evidence that the structural variation in rumbles reflects the individual identity, reproductive state, and emotional state of callers. Growth in knowledge about the communication system of the African elephant has occurred from a rich combination of research on wild elephants in national parks and captive elephants in zoological parks.
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Affiliation(s)
- Joseph Soltis
- Education and Science, Disney's Animal Kingdom, Bay Lake, Florida, USA.
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18
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Shyan-Norwalt MR, Peterson J, Milankow King B, Staggs TE, Dale RHI. Initial findings on visual acuity thresholds in an African elephant (Loxodonta africana). Zoo Biol 2009; 29:30-5. [PMID: 19598240 DOI: 10.1002/zoo.20259] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
There are only a few published examinations of elephant visual acuity. All involved Asian elephants (Elephas maximus) and found visual acuity to be between 8' and 11' of arc for a stimulus near the tip of the trunk, equivalent to a 0.50 cm gap, at a distance of about 2 m from the eyes. We predicted that African elephants (Loxodonta africana) would have similarly high visual acuity, necessary to facilitate eye-trunk coordination for feeding, drinking and social interactions. When tested on a discrimination task using Landolt-C stimuli, one African elephant cow demonstrated a visual acuity of 48' of arc. This represents the ability to discriminate a gap as small as 2.75 cm in a stimulus 196 cm from the eye. This single-subject study provides a preliminary estimate of the visual acuity of African elephants.
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Hill PSM. How do animals use substrate-borne vibrations as an information source? Naturwissenschaften 2009; 96:1355-71. [PMID: 19593539 DOI: 10.1007/s00114-009-0588-8] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2008] [Revised: 06/15/2009] [Accepted: 06/30/2009] [Indexed: 11/26/2022]
Abstract
Animal communication is a dynamic field that promotes cross-disciplinary study of the complex mechanisms of sending and receiving signals, the neurobiology of signal detection and processing, and the behaviors of animals creating and responding to encoded messages. Alongside visual signals, songs, or pheromones exists another major communication channel that has been rather neglected until recent decades: substrate-borne vibration. Vibrations carried in the substrate are considered to provide a very old and apparently ubiquitous communication channel that is used alone or in combination with other information channels in multimodal signaling. The substrate could be 'the ground', or a plant leaf or stem, or the surface of water, or a spider's web, or a honeybee's honeycomb. Animals moving on these substrates typically create incidental vibrations that can alert others to their presence. They also may use behaviors to create vibrational waves that are employed in the contexts of mate location and identification, courtship and mating, maternal care and sibling interactions, predation, predator avoidance, foraging, and general recruitment of family members to work. In fact, animals use substrate-borne vibrations to signal in the same contexts that they use vision, hearing, touch, taste, or smell. Study of vibrational communication across animal taxa provides more than just a more complete story. Communication through substrate-borne vibration has its own constraints and opportunities not found in other signaling modalities. Here, I review the state of our understanding of information acquisition via substrate-borne vibrations with special attention to the most recent literature.
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O'Connell-Rodwell CE. Keeping an "ear" to the ground: seismic communication in elephants. Physiology (Bethesda) 2007; 22:287-94. [PMID: 17699882 DOI: 10.1152/physiol.00008.2007] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This review explores the mechanisms that elephants may use to send and receive seismic signals from a physical, anatomical, behavioral, and physiological perspective. The implications of the use of the vibration sense as a multimodal signal will be discussed in light of the elephant's overall fitness and survival.
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Bouley DM, Alarcón CN, Hildebrandt T, O'Connell-Rodwell CE. The distribution, density and three-dimensional histomorphology of Pacinian corpuscles in the foot of the Asian elephant (Elephas maximus) and their potential role in seismic communication. J Anat 2007; 211:428-35. [PMID: 17711421 PMCID: PMC2375831 DOI: 10.1111/j.1469-7580.2007.00792.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Both Asian (Elephas maximus) and African (Loxodonta africana) elephants produce low-frequency, high-amplitude rumbles that travel well through the ground as seismic waves, and field studies have shown that elephants may utilize these seismic signals as one form of communication. Unique elephant postures observed in field studies suggest that the elephants use their feet to 'listen' to these seismic signals, but the exact sensory mechanisms used by the elephant have never been characterized. The distribution, morphology and tissue density of Pacinian corpuscles, specialized mechanoreceptors, were studied in a forefoot and hindfoot of Asian elephants. Pacinian corpuscles were located in the dermis and distal digital cushion and were most densely localized to the anterior, posterior, medial and lateral region of each foot, with the highest numbers in the anterior region of the forefoot (52.19%) and the posterior region of the hindfoot (47.09%). Pacinian corpuscles were encapsulated, had a typical lamellar structure and were most often observed in large clusters. Three-dimensional reconstruction through serial sections of the dermis revealed that individual Pacinian corpuscles may be part of a cluster. By studying the distribution and density of these mechanoreceptors, we propose that Pacinian corpuscles are one possible anatomic mechanism used by elephants to detect seismic waves.
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Affiliation(s)
- D M Bouley
- Department of Comparative Medicine, Stanford University School of Medicine, Stanford, CA, USA.
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O'Connell-Rodwell CE, Wood JD, Kinzley C, Rodwell TC, Poole JH, Puria S. Wild African elephants (Loxodonta africana) discriminate between familiar and unfamiliar conspecific seismic alarm calls. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2007; 122:823-30. [PMID: 17672633 DOI: 10.1121/1.2747161] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The ability to discriminate between call types and callers as well as more subtle information about the importance of a call has been documented in a range of species. This type of discrimination is also important in the vibrotactile environment for species that communicate via vibrations. It has recently been shown that African elephants (Loxodonta africana) can detect seismic cues, but it is not known whether they discriminate seismic information from noise. In a series of experiments, familiar and unfamiliar alarm calls were transmitted seismically to wild African elephant family groups. Elephants respond significantly to the alarm calls of familiar herds (p=0.004) but not to the unfamiliar calls and two different controls, thus demonstrating the ability of elephants to discriminate subtle differences between seismic calls given in the same context. If elephants use the seismic environment to detect and discriminate between conspecific calls, based on the familiarity of the caller or some other physical property, they may be using the ground as a very sophisticated sounding board.
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Affiliation(s)
- Caitlin E O'Connell-Rodwell
- Department of Otolaryngology, Head and Neck Surgery, Stanford University School of Medicine, Stanford, California 94305-5739, USA.
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