Cylinder wall thickness difference discrimination by an echolocating Atlantic bottlenose dolphin

• Published in: Journal of Comparative Physiology A 1992, Vol.170 (1), p.41-47
• Main Authors: AU, W. W. L, PAWLOSKI, D. A
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Cetacea; Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation; Fundamental and applied biological sciences. Psychology; Marine; Tursiops truncatus; Vertebrates: nervous system and sense organs
• ISSN: 0340-7594; 1432-1351
• DOI: 10.1007/BF00190399

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 plus or minus 0.2, plus or minus 0.3, plus or minus 0.4, and plus or minus 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 plus or minus 11 degree 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. 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. Back-scatter 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 plus or minus 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.