Composite Training Unit Exercises and Joint Task ... - Govsupport.us

CD-086-06, Navy Training ExercisesSouthern CaliforniaPage 27of two studies and one after-the-fact investigation wherein the naturalbehavior patterns of marine mammals exposed to levels of tactical midfrequencysonar, or sounds similar to mid-frequency sonar, lower thanthose thought to induce TTS were disrupted to the point where it wasabandoned or significantly altered:(1) Finneran and Schlundt (2004) analyzed behavioral observationsfrom related TTS studies (Schlundt et al., 2000; Finneran et al., 2001;2003) to calculate cetacean behavioral reactions as a function of knownnoise exposure. During the TTS experiments, four dolphins and two whitewhales were exposed during a total of 224 sessions to 1-s pulsesbetween 160 and 204 dB re 1 mPa (root-mean-square sound pressure level(SPL)), at 0.4, 3, 10, 20, and 75 kHz. Finneran and Schlundt (2004)evaluated the behavioral observations in each session and determinedwhether a ``behavioral alteration'' (ranging from modifications ofresponse behavior during hearing sessions to attacking the experimentalequipment) occurred. For each frequency, the percentage of sessions inwhich behavioral alterations occurred was calculated as a function ofreceived noise SPL. By pooling data across individuals and testfrequencies, respective SPL levels coincident with responses by 25, 50,and 75 percent behavioral alteration were documented. 190 dB re 1 mPa(SPL) is the point at which 50 percent of the animals exposed to 3, 10,and 20 kHz tones were deemed to respond with some behavioralalteration, and the threshold that the Navy originally proposed forsub-TTS behavioral disturbance.(2) Nowacek et al. (2004) conducted controlled exposure experimentson North Atlantic right whales using ship noise, social sounds of conspecifics,and an alerting stimulus (frequency modulated tonal signalsbetween 500 Hz and 4.5 kHz). Animals were tagged with acoustic sensors(D-tags) that simultaneously measured movement in three dimensions.Whales reacted strongly to alert signals at received levels of 133-148dB SPL, mildly to conspecific signals, and not at all to ship sounds oractual vessels. The alert stimulus caused whales to immediately ceaseforaging behavior and swim rapidly to the surface. Although SEL valueswere not directly reported, based on received exposure durations,approximate received values were on the order of 160 dB re: 1 mPa\2\-s.(3) NMFS (2005) evaluated the acoustic exposures and coincidentbehavioral reactions of killer whales in the presence of tactical midfrequencysonar. In this case, none of the animals were directly fittedwith acoustic dosimeters. However, based on a Naval Research Laboratory(NRL) analysis that took advantage of the fact that calibrated