The objective of this study was to measure the ability of the sea lion (Zalophuscalifornianus) to localize click and pulsed pure−tone signals presented in the horizontal plane. In the first experiment the Minimum Audible Angle (MAA) was determined for a click signal consisting of one cycle of a 1.0−kHz signal presented with a repetition rate of 30 Hz. Thresholds at 63% and 75% correct responses were 6° and 9°, respectively. A second experiment examined the sea lion’s ability to localize pulsed pure tones ranging in frequency from 0.25 to 4.0 kHz at only one angular displacement. The pure tones were presented in the form of a pulse train, each pulse having a duration of 20 msec, rise−fall time of 5 msec, and a repetition rate of 30 Hz. The pulsed pure−tone localization function showed that as signal frequency was increased from 250 Hz to 1.0 kHz, the sea lion’s ability to localize the signal remained relatively constant, while above 1.0 kHz there was a sharp decrement in localization ability.

Subject Classification: 65.62; 80.60.

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