MAXIMUM DETECTION RANGE AND RANGE RESOLUTION IN ECHOLOCATING BOTTLENOSE PORPOISES, TURSIOPS TRUNCATUS (MONTAGU)

Behaviorally mediated, psychological measurements of the maximum range (distance) of object detection by two echolocating bottleness porpoises (Tursiops truncatus) and the range resolution ability of a third echolocating bottlenose porpoise were made. These tests were conducted with animals kept in floating, wire mesh pens acoustically open to Kaneohe Bay, Oahu, Hawaii at the Naval Ocean System Center's Hawaii facilities.; In order to determine the maximum range of object detection, two male bottlenose porpoises were conditioned to report the presence or absence of metallic spheres suspended beneath the surface of the water along an open water range extending from their enclosure. Probability of detection as a function of target-object distance was determined utilizing three different target spheres. The experiments designed to determine the maximum ranges of detection by the porpoises of a 2.54 cm diameter, solid steel sphere and a 7.62 cm diameter, steel, water-filled sphere were conducted with the spheres suspended 1.2 m beneath the surface of the water. During an experiment designed to test the affects of target depth (or nearness to the bottom) on the porpoises' maximum range of detection a 6.35 cm diameter, solid steel sphere was suspended at five depths (1.2 m, 2.4 m, 3.7 m, 4.9 m and on the bottom). Echolocation range of detection curves were determined for all of these target depths.; The maximum range of object detection task was of two alternative, forced-choice, successive target presentation, spatially separated "present or absent" response design. Hit rate (correct target-present responses) and false alarm rates (incorrect target-present responses) were determined for the 2.54 cm sphere at 12 distance increments (from the porpoises' echolocation station within their pen) from 18.3 m to 74.9 m. The animal's hit rates and false alarm rates were determined for the 7.63 cm sphere at 9 distance increments (36.6 m to 77.7 m). Hit rates and false alarm rates were determined for the 6.35 cm target at 5 distance increments (71.3 m to 74.9 m) when it was suspended 1.2 m beneath the surface of the water, 7 distance increments (68.6 m to 75.9 m) with a 2.4 m target depth, 8 distance increments (68.6 m to 74.9 m) with a 3.6 m target depth, 7 distance increments (67.6 m to 73.1 m) with a 4.8 m target depth and 8 distance increments (65.8 m to 72.2 m) with the target on the bottom. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI...