The results of a study to determine the pulsed pure‐tone sound‐localization capability of a California sea lion, Zalophuscalifornianus, in the horizontal plane are presented. The minimum audible angle (MAA) was determined as a function of frequency from 0.5 to 16 kHz in 1‐octave steps. The results suggested that the animal utilized time‐difference cues for the lower frequencies (0.5 to 1.0 kHz) and intensity‐difference cues for the higher frequencies (4.0 to 16.0 kHz). The MAAs for the lower frequencies were smaller than for the higher frequencies, and for the transitional frequencies (2.0 to 4.0 kHz) the animal experienced extreme difficulties in localizing the sound. To further investigate the effects of sound intensity difference in the localization process, an experiment using a sea lion skull with hydrophones attached close to each bulla was conducted. Intensity differences were measured with the skull directed at different azimuths in relatioship to a sound source. The results of the measurements using the skull considered together with the behavioral data support the contention that the sea lion used both time and intensity cues for underwater localization.

Subject Classification: 65.62; 80.50.

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