Not so far: attenuation of low-frequency vocalizations in a rainforest environment suggests limited acoustic mediation of social interaction in African forest elephants

  • Daniela Hedwig
  • Maya DeBellis
  • Peter Howard Wrege
Original Article


Forest elephants Loxodonta cyclotis aggregate in large numbers in forest clearings. Whether they maintain contact as they move through the forest and are able to coordinate these aggregations, similar to the fission-fusion sociality of the well-studied savanna elephants Loxodonta africana, is currently unknown. Since sound attenuates faster in closed as compared to open habitats, the low-frequency rumble vocalizations of forest elephants may exhibit smaller detection ranges than measured for those of savanna elephants, which may restrict the ability of forest elephants to coordinate interactions between separated family units. Here, we modeled the attenuation of forest elephant rumbles using amplitude measurements of rumbles recorded in a rainforest in Gabon and estimated the distances at which elephants might be able to detect them under observed ambient sound conditions. Our results suggest an attenuation rate less than predictions of spherical spreading loss, suggesting that reflection of the sound waves within the forest results in constructive interference. Nevertheless, we found that forest elephant rumbles of average dominant frequency (31.07 Hz) under average ambient sound levels would not be detectable farther than 0.8 km. Moreover, for 50% of analyzed rumbles, the harmonic structure was completely attenuated at only 100 m. However, we estimated detection distances of up to 3.2 km for rumbles of average dominant frequency when ambient sound was at its lowest. Our findings suggest that long-distance communication to coordinate interactions among separated family units may be limited in forest elephants, with potentially important consequences for their social organization.

Significance statement

The challenges associated with the extent of, and variation in, detection distances of long-distance vocalizations used by animals to mediate interactions between separated group members has rarely been investigated. While it has been suggested that forest elephants exhibit a fission-fusion sociality similar to savanna elephants, our results indicate shorter detection distances for forest elephant rumbles, suggesting a limited ability to mediate interactions between separated family units. However, under optimal ambient sound conditions, detection distances increased considerably. The long detection distances estimated for savanna elephants may reflect the optimal conditions under which the playback experiments were conducted. On average, savanna elephants may be much more limited in communication distance. Further studies on the constraints and opportunities that the different environments impose on these species’ communication capability may be critical to understanding potential differences in the social complexity they express.


Ambient noise Vocal communication Detection distance Fission-fusion Acoustic adaptation 



This study was supported by a grant to PHW from the US Fish and Wildlife Service, the Robert G. and Jane V. Engle Foundation, and through a generous gift from Lisa Yang to the Cornell Lab of Ornithology. Research clearance was approved by the Gabon government’s Centre National de la Recherché Scientifique et Technologique. We thank the reviewers for their careful review and very useful suggestions. Special thanks go to Abbey Doyno for analysis help; Yu Shiu, Holger Klinck, and Dean Hawthorne for discussions; Lynn Marie Johnson for statistical advice; Elizabeth D. Rowland and Herve Londo for superb assistance with data collection; and Precious Woods Gabon for critical logistics support.

Compliance with ethical standards

Ethical approval

This work was carried out using a non-invasive method, which required no direct observations or contact with the animals. This research was conducted in accordance with the national laws of the Republic of Gabon. Research clearance was approved by the Gabon government’s Centre National de la Recherché Scientifique et Technologique.

Conflict of interest

The authors declare that they have no conflicts of interest.

Supplementary material

265_2018_2451_MOESM1_ESM.pdf (47 kb)
ESM 1 (PDF 46.7 kb)
265_2018_2451_MOESM2_ESM.pdf (166 kb)
ESM 2 (PDF 166 kb)
265_2018_2451_MOESM3_ESM.pdf (52 kb)
ESM 3 (PDF 51.8 kb)


  1. Archie EA, Moss CJ, Alberts SC (2006) The ties that bind: genetic relatedness predicts the fission and fusion of social groups in wild African elephants. Proc R Soc Lond B 273(1586):513–522. CrossRefGoogle Scholar
  2. Aureli F, Schaffner CM, Boesch C et al (2008) Fission-fusion dynamics: new research frameworks. Curr Anthropol 49:627–654Google Scholar
  3. Baotic A, Stoeger AS (2017) Sexual dimorphism in African elephant social rumbles. PLoS One 12(5):e0177411. CrossRefPubMedPubMedCentralGoogle Scholar
  4. Bee MA, Micheyl C (2008) The cocktail party problem: what is it? How can it be solved? And why should animal behaviorists study it? J Comp Psychol 122(3):235–251. CrossRefPubMedPubMedCentralGoogle Scholar
  5. Bradbury JW, Vehrencamp SL (2011) Principles of animal communication. Sinauer Associates, SunderlandGoogle Scholar
  6. Brenowitz EA (1982) The active space of red-winged blackbird song. J Comp Physiol 147(4):511–522. CrossRefGoogle Scholar
  7. Brumm H, Zollinger SA (2011) The evolution of the Lombard effect: 100 years of psychoacoustic research. Behaviour 148(11):1173–1198. CrossRefGoogle Scholar
  8. Calupca TA, Fristrup KM, Clark CW (2000) A compact digital recording system for autonomous bioacoustic monitoring. J Acoust Soc Am 108(5):2582–2582. CrossRefGoogle Scholar
  9. Charif RA, Ramey RR, Langbauer WR, Payne KP, Martin RB, Brown LM (2005) Spatial relationships and matrilineal kinship in African savanna elephant (Loxodonta africana) clans. Behav Ecol Sociobiol 57(4):327–338. CrossRefGoogle Scholar
  10. Charlton BD, Reby D, Ellis WA, Brumm J, Fitch WT (2012) Estimating the active space of male koala bellows: propagation of cues to size and identity in a eucalyptus forest. PLoS One 7(9):e45420. CrossRefPubMedPubMedCentralGoogle Scholar
  11. Eckhardt N, Polansky L, Boesch C (2015) Spatial cohesion of adult male chimpanzees (Pan troglodytes verus) in Taï National Park, Côte d’Ivoire. Am J Primatol 77(2):125–134. CrossRefPubMedGoogle Scholar
  12. Erbe C, Reichmuth C, Cunningham K, Lucke K, Dooling R (2016) Communication masking in marine mammals: a review and research strategy. Mar Pollut Bull 103:15–38CrossRefPubMedGoogle Scholar
  13. Ey E, Rahn C, Hammerschmidt K, Fischer J (2009) Wild female olive baboons adapt their grunt vocalizations to environmental conditions. Ethology 115(5):493–503. CrossRefGoogle Scholar
  14. Fay R (1988) Hearing in vertebrates—a psychophysics Databook. Hill-Fay Associates, WinnetkaGoogle Scholar
  15. Figueroa H, Robbins M (2008) XBAT: an open-source extensible platform for bioacoustic research and monitoring. In: Frommolt K-H, Bardeli R, Clausen M (eds) Computational bioacoustics for assessing biodiversity. Bundesamt für Naturschutz, Bonn, pp 143–155Google Scholar
  16. Fishlock V, Lee PC (2013) Forest elephants: fission–fusion and social arenas. Anim Behav 85(2):357–363. CrossRefGoogle Scholar
  17. Fishlock V, Schuttler S, Breuer T (2015) Forest elephant biology and behaviour: research questions for conservation. In: Fischlock V, Breuer T (eds) Studying Forest elephants. Neuer Sportverlag, Stuttgart, pp 32–41Google Scholar
  18. Fletcher H (1940) Auditory patterns. Rev Mod Phys 12(1):47–65. CrossRefGoogle Scholar
  19. Garcia-Rutledge EJ, Narins PM (2001) Shared acoustic resources in an old world frog community. Herpetologica 57(1): 104–116Google Scholar
  20. Garstang M, Larom D, Raspet R, Lindeque M (1995) Atmospheric controls on elephant communication. J Exp Biol 198(Pt 4):939–951PubMedGoogle Scholar
  21. Heffner RS, Heffner HE (1982) Hearing in the elephant (Elephas maximus): absolute sensitivity, frequency discrimination, and sound localization. J Comp Physiol Psychol 96(6):926–944. CrossRefPubMedGoogle Scholar
  22. Janik VM (2000) Source levels and the estimated active space of bottlenose dolphin (Tursiops truncatus) whistles in the Moray Firth, Scotland. J Comp Physiol A 186(7-8):673–680. CrossRefPubMedGoogle Scholar
  23. Langbauer WR, Payne KB, Charif RA, Rapaport L, Osborn F (1991) African elephants respond to distant playbacks of low-frequency conspecific calls. J Exp Biol 157:35–46Google Scholar
  24. Larom D, Garstang M, Lindeque M, Raspet R, Zunckel M, Hong Y, Brassel K, O'Beirne S (1997) Meteorology and elephant infrasound at Etosha National Park, Namibia. J Acoust Soc Am 101(3):1710–1717. CrossRefGoogle Scholar
  25. Marten K, Marler P (1977) Sound transmission and its significance for animal vocalization. Behav Ecol Sociobiol 2(3):271–290. CrossRefGoogle Scholar
  26. McComb K, Moss C, Sayialel S, Baker L (2000) Unusually extensive networks of vocal recognition in African elephants. Anim Behav 59(6):1103–1109. CrossRefPubMedGoogle Scholar
  27. McComb K, Reby D, Baker L, Moss C, Sayialel S (2003) Long-distance communication of acoustic cues to social identity in African elephants. Anim Behav 65(2):317–329. CrossRefGoogle Scholar
  28. Mennill DJ, Burt JM, Fristrup KM, Vehrencamp SL (2006) Accuracy of an acoustic location system for monitoring the position of duetting songbirds in tropical forest. J Acoust Soc Am 119(5):2832–2839. CrossRefPubMedPubMedCentralGoogle Scholar
  29. Miller PJO (2006) Diversity in sound pressure levels and estimated active space of resident killer whale vocalizations. J Comp Physiol A 192(5):449–459. CrossRefGoogle Scholar
  30. Moore BC (ed) (1995) Hearing. Academic Press, San DiegoGoogle Scholar
  31. Morton ES (1975) Ecological sources of selection on avian sounds. Am Nat 109(965):17–34. CrossRefGoogle Scholar
  32. Nemeth E, Dabelsteen T, Pedersen SB, Winkler H (2006) Rainforests as concert halls for birds: are reverberations improving sound transmission of long song elements? J Acoust Soc Am 119(1):620–626. CrossRefPubMedGoogle Scholar
  33. Payne K (2003) Sources of social complexity in the three elephant species. In: de Waal FBM, Tyak PL (eds) Animal social complexity: intelligence, culture, and individualized societies. Harvard University Press, Cambridge, pp 57–85. CrossRefGoogle Scholar
  34. Poole JH (2011) Behavioral contexts of elephant acoustic communication. In: Moss CJ, Croze H, Lee PC (eds) The Amboseli elephants: a long-term perspective on a long-lived mammal. University of Chicago Press, Chicago, pp 125–161. CrossRefGoogle Scholar
  35. Poole JH, Payne K, Langbauer WR, Moss CJ (1988) The social contexts of some very low frequency calls of African elephants. Behav Ecol Sociobiol 22(6):385–392. CrossRefGoogle Scholar
  36. R Core Team (2016) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, AustriaGoogle Scholar
  37. Sakai H, Sato S, Ando Y (1998) Orthogonal acoustical factors of sound fields in a forest compared with those in a concert hall. J Acoust Soc Am 104(3):1491–1497. CrossRefGoogle Scholar
  38. Soltis J, Leong K, Savage A (2005) African elephant vocal communication II: rumble variation reflects the individual identity and emotional state of callers. Anim Behav 70:589–599CrossRefGoogle Scholar
  39. Soltis J, Leighty KA, Wesolek CM, Savage A (2009) The expression of affect in African elephant (Loxodonta africana) rumble vocalizations. J Comp Psychol 123(2):222–225. CrossRefPubMedGoogle Scholar
  40. Soltis J, King LE, Douglas-Hamilton I, Vollrath F, Savage A (2014) African elephant alarm calls distinguish between threats from humans and bees. PLoS One 9(2):e89403. CrossRefPubMedPubMedCentralGoogle Scholar
  41. Spehar SN, Di Fiore A (2013) Loud calls as a mechanism of social coordination in a fission–fusion taxon, the white-bellied spider monkey (Ateles belzebuth). Behav Ecol Sociobiol 67(6):947–961. CrossRefGoogle Scholar
  42. Stoeger AS, Heilmann G, Zeppelzauer M, Ganswindt A, Hensman S, Charlton BD (2012) Visualizing sound emission of elephant vocalizations: evidence for two rumble production types. PLoS One 7(11):e48907. CrossRefPubMedPubMedCentralGoogle Scholar
  43. Thompson M (2009) African forest elephant (Loxodonta africana cyclotis) vocal behavior and its use in conservation. PhD thesis, Cornell UniversityGoogle Scholar
  44. Todd NPM (2007) Estimated source intensity and active space of the American alligator (Alligator Mississippiensis) vocal display. J Acoust Soc Am 122(5):2906–2915. CrossRefPubMedGoogle Scholar
  45. Turkalo AK, Fay JM (2001) Forest elephant behavior and ecology. Yale University Press, New HavenGoogle Scholar
  46. Turkalo AK, Wrege PH, Wittemyer G (2013) Long-term monitoring of Dzanga Bai forest elephants: forest clearing use patterns. PLoS One 8(12):e85154. CrossRefPubMedPubMedCentralGoogle Scholar
  47. Verhey JL, Pressnitzer D, Winter IM (2003) The psychophysics and physiology of comodulation masking release. Exp Brain Res 153:405–417CrossRefPubMedGoogle Scholar
  48. Von Békésy G, Wever EG (1960) Experiments in hearing. McGraw-Hill, New YorkGoogle Scholar
  49. Wittemyer G, Douglas-Hamilton I, Getz WM (2005) The socioecology of elephants: analysis of the processes creating multitiered social structures. Anim Behav 69:1357–1371CrossRefGoogle Scholar
  50. Wood JD, McCowan B, Langbauer WR Jr, Viljoen JJ, Hart LA (2005) Classification of African elephant Loxodonta africana rumbles using acoustic parameters and cluster analysis. Bioacoustics 15(2):143–161. CrossRefGoogle Scholar
  51. Wrege PH, Rowland ED, Keen S, Shiu Y (2017) Acoustic monitoring for conservation in tropical forests: examples from forest elephants. Methods Ecol Evol (published online, doi:10.1111/2041-210X.12730).

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Elephant Listening Project, Bioacoustics Research Program, Cornell Lab of OrnithologyCornell UniversityIthacaUSA

Personalised recommendations