White whales (Delphinapterus leucas), like other cetaceans, evolved from land-dwelling mammals; their ears are especially remarkable in that a high state of development of the auditory system was crucial to their success as ocean predators; we do not as yet understand how these descendants of aerial ears and related nervous and motor systems function at depth. Although there are few reports on hearing and sonar in most marine mammals, several studies have been conducted on the white whale. All have been done near the surface; thus, a good baseline exists. Little is known about whale hearing and sonar at depth -knowledge necessary to assess the effects of ocean-basin magnitude low-frequency sound on deep divers. We have planned a study that should supply crucial data and observations on whale hearing, sonar, neural and motor systems, physiology, and diving capabilities. This understanding is critical if ocean researchers and industrial operators are to be good stewards of marine ecosystems.

We will show a video of how we will carry out a study in the open ocean with trained whales being tested at the surface and then diving variously to depths of 100, 200, and 300 meters. The hearing and echolocation abilities of the trained white whale will be tested at the ocean surface by methods employed in current and previous studies. The test apparatus will then be lowered to depth and the whale will swim down to a station where it will be tested at depth. Observations will be collected by hydrophores and video cameras on the apparatus and physiological monitoring packages attached to the animal can provide data including EKG, micro vibrations, skin temperature and other physiological variables. The preliminary results of the first seven-week study conducted off San Clemente Island, California will be presented.

Two trained whales (MUK and NOC) followed a small zodiac from enclosures located in 20-30 m water depth near shore to deep water within one mile. On command, the whales made dives to a test apparatus beneath the work boat. After one to ten minutes at the apparatus, during which they received hearing test tones through the underwater cable and hydrophore, an SD signal was sounded and the whale returned to the surface for a fish reward. While on the underwater apparatus, each time a whale hears the tone it whistles in response. After surfacing from the last dive, the whale presents its flukes so that a blood sample can be taken.