Subject(s)
Dark Adaptation , Eye Movements , Vision, Ocular , Electrooculography , Female , Humans , Motion Perception , Photic Stimulation , PsychophysicsABSTRACT
Conditioning techniques were developed demonstrating that pure tone frequencies under water can exert nearly perfect control over the underwater click vocalizations of the California sea lion (Zalophus californianus). Conditioned vocalizations proved to be a reliable way of obtaining underwater sound detection thresholds in Zalophus at 13 different frequencies, covering a frequency range of 250 to 64,000 Hz. The audiogram generated by these threshold measurements suggests that under water, the range of maximal sensitivity for Zalophus lies between one and 28 kHz with best sensitivity at 16 kHz. Between 28 and 36 kHz there is a loss in sensitivity of 60 dB/octave. However, with relatively intense acoustic signals (> 38 dB re 1 mub underwater), Zalophus will respond to frequencies at least as high as 192 kHz. These results are compared with the underwater hearing of other marine mammals.
Subject(s)
Audiometry , Caniformia , Conditioning, Psychological , Vocalization, Animal , Animals , Auditory Perception , Differential Threshold , Ear/anatomy & histology , Hearing , Immersion , Male , SoundSubject(s)
Visual Acuity , Adaptation, Physiological , Animals , Asia , Environment , Male , MammalsSubject(s)
Behavior, Animal , Caniformia/physiology , Light , Orientation , Visual Acuity , Adaptation, Ocular , Animals , California , Male , Marine BiologyABSTRACT
Aerial visual acuity and underwater visual acuity were measured in two sea lions (Zalophus californianus) by training them to emit click bursts if they saw a striped target or to remain silent if they saw a gray target. The closest grating spacings that could be resolved both in air and under water subtended a visual angle of 5.5 minutes of arc at a distance of 5.5 meters.
