HEARING DEFICITS MEASURED IN SOME TURSIOPS-TRUNCATUS, AND DISCOVERY OF A DEAF MUTE DOLPHIN/

Eight bottlenose dolphins Tursiops truncatus (four male, four female) were trained to respond to 100-ms tones. Three male dolphins (ages 23, 26, and 34) exhibited hearing disability at four higher frequencies - 70, 80, 100, and 120 kHz even at 111-135 dB re:1 mu Pa. Two females ( ages 32 and 35) responded to all frequencies as did a male (age 7) and a female (age 11). One female (age 33) responded to all tones at 80 k Hz and below; however, she failed to respond at 100 or 120 kHz. One yo ung female dolphin (age 9) exhibited no perception of sound to behavio ral or electrophysiological tests. This young female was not only deaf , but mute. The dolphin was monitored periodically by hydrophone and d aily by trainers (by ear in air) for 7 years until she was age 16. The animal never whistled or made echolocation pulses or made burst pulse sounds as other dolphins do.