Journal of Comparative Physiology A

, Volume 170, Issue 1, pp 41–47 | Cite as

Cylinder wall thickness difference discrimination by an echolocating Atlantic bottlenose dolphin

  • Whitlow W. L. Au
  • Deborah A. Pawloski


The capability of an Atlantic bottlenose dolphin Tursiops truncatus to discriminate wall thickness differences of hollow cylinders by echolocation was studied. A standard cylinder of 6.35 mm wall thickness was compared with cylinders having wall thicknesses that differed from the standard by ± 0.2, ± 0.3, ± 0.4, and ± 0.8 mm. All cylinders had an O.D. of 37.85 mm, and a length of 12.7 cm. The dolphin was required to station in a hoop while the standard and comparison targets, separated by an angle of ± 11° from a center line, were simultaneously presented at a range of 8 m. The dolphin was required to echolocate and indicate the side of the standard target. Target location on each trial was randomized. Interpolation of the dolphin performance data indicated a wall thickness discrimination threshold (at the 75% correct response level) of −0.23 mm and +0.27 mm. Backscatter measurements suggest that if the dolphin used time domain echo cues, it may be able to detect time differences between two echo highlights to within approximately ± 500 ns. If frequency domain cues were used, the dolphin may be able to detect frequency shifts as small as 3 kHz in a broadband echo having a center frequency of approximately 110 kHz. Finally, if the dolphin used time-separation pitch (TSP) cues, it may be able to detect TSP differences of approximately 450 Hz.

Discrimination tests with the thinner comparison targets were also conducted in the presence of broadband masking noise. For an echo energy-to-noise ratio of 19 dB the dolphin's performance was comparable to its noise-free performance. At an energy-to-noise ratio of 14 dB the dolphin was unable to achieve the 75% correct threshold with any of the comparison targets.

Key words

Thickness difference discrimination Echolocation Bottlenose dolphin 



sound velocity


receive directivity index


difference between highlight intervals of two targets


wall thickness difference between standard and comparison targets;


energy flux density


echo energy flux density


echo energy to noise ratio


frequency spectrum of artificial echo


artificial echo


ambient noise spectral density


received noise spectral density


outer diameter


instantaneous acoustic pressure


target range


source energy flux density in dB


dolphin sonar signal


time between first and second echo highlights


target strength based on energy


time-separation pitch


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  1. Au WWL (1988a) Sonar target detection and recognition by odontocetes. In: Nachtigall PE, Moore PWB (eds) Animal sonar: Processes and performance, Plenum, New York, pp 451–465Google Scholar
  2. Au WWL (1988b) Detection and recognition models of dolphin sonar systems. In: Nachtigall PE, Moore PWB (eds) Animal sonar: Processes and performance, Plenum, New York, pp 753–768Google Scholar
  3. Au WWL, Hammer CE Jr (1980) Target recognition via echolocation by Tursiops truncatus. In: Busnel RG, Fish JF (eds) Animal sonar systems. Plenum New York, pp 855–858Google Scholar
  4. Au WWL, Martin DW (1988) Sonar discrimination of metallic plates. In: Nachtigall PE, Moore PWB (eds) Animal sonar: Processes and performance, Plenum, New York, pp 809–813Google Scholar
  5. Au WWL, Martin DW (1989) Insights in dolphin discrimination capabilities from human listening experiments, J Acoust Soc Am 86:1662–1670Google Scholar
  6. Au WWL, Pawloski JL (1989) Detection of ripple noise by an Atlantic bottlenose dolphin. J Acoust Soc Am 86:591–596Google Scholar
  7. Au WWL, Snyder (1980) Long-range target detection in open waters by an echolocating Atlantic bottlenose dolphin (Tursiops truncatus), J Acoust Soc Am 68:1077–1084Google Scholar
  8. Ayrapet'yants ES, Konstantinov AI (1974) Echolocation in nature.Nauka, LeningradGoogle Scholar
  9. Bel'kovich VM, Dubrovskiy NA (1976) Sensory bases of cetacean orientation. Nauka, LeningradGoogle Scholar
  10. Evans WE, Powell BA (1967) Discrimination of different metallic plates by an echolocating delphinid. In: Busnel RG (ed) Animal sonar systems: biology and bionics. Laboratoire de Physiologie Acoustique, Jouy-en-Josas, France, pp 363–383Google Scholar
  11. Hammer CEJr, Au WWL (1980) Porpoise echo-recognition: An analysis of controlling target characteristics. J Acoust Soc Am 68:1285–1293Google Scholar
  12. Kinsler LE, Frey AR, Coppens AB, Sanders JV (1982) Fundamentals of acoustics. John Wiley & Son, New YorkGoogle Scholar
  13. Nachtigall PE (1980) Odontocete echolocation performance of object size, shape and material. In: Busnel RG, Fish JF (eds) Animal sonar systems. Plenum, New York, pp 71–95Google Scholar
  14. Otnes RK, Enochson L (1978) Applied time series analysis, vol 1. John Wiley, New York, pp 27–29Google Scholar
  15. Rihaczek AW (1969) Principles of high-resolution radar. McGraw-Hill New York, pp 15–20Google Scholar
  16. Thompson RKR, Herman LM (1975) Underwater frequency discrimination in the bottlenose dolphin (1–140 kHz) and the human (1–8 kHz). J Acoust Soc Am 57:943–948Google Scholar
  17. Thurlow WR (1957) Further observation on pitch associated with a time difference between two pulse trains. J Acoust Soc Am 29:1310–1311Google Scholar
  18. Titov AA (1972) Investigation of sonic activity and phenomenological characteristics of the echolocation analyzer of Black Sea delphinids. Canditorial Dissert., KaradagGoogle Scholar

Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • Whitlow W. L. Au
    • 1
  • Deborah A. Pawloski
    • 2
  1. 1.Naval Ocean Systems Center KailuaHawaiiUSA
  2. 2.SEACO Division of SAIC KailuaHawaiiUSA

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