Sonar

Sonar (SOund Navigation And Ranging) is the name of a technology that is used to detect objects in water and within the seafloor. There are two basic types – passive and active. Passive sonars listen for underwater sounds. Active sonar systems emit sounds and use returning echoes to detect, locate, and classify objects in the environment. For example, differences among echoes are used to determine whether an object is a submarine, rock outcrop, school of fish, or a whale. There is concern that active sonar systems may affect marine animals.

Active sonar example. Copyright University of Rhode Island

 

This recording is of an active sonar that is tracking a close target. Sound courtesy of J & A Enterprises.

Active sonars are categorized based on the frequency of the signals that they transmit. Common divisions are: low-frequency (less than 1 kHz), mid-frequency (1 to 10 kHz), and high-frequency (greater than 10 kHz). The differences in frequencies affect the distance to which the sounds will travel, with low-frequency signals typically traveling much farther than high-frequency signals.

In addition to different frequencies, sonars can emit signals with different waveforms and durations. For example, tones may be transmitted at a single frequency, frequency-modulated (FM) upsweeps or downsweeps. These signals range from continuous active sonar (CAS) to short duration pulses of less than one second.

Because marine animals vary in their hearing sensitivities, both the frequency and duration characteristics of sonar systems are important factors about what species may be affected by any given sonar signal. Thus, it is important to consider the sound source and its transmissions, as well as the species likely to be exposed to determine the potential effects.

Potential Effects: Fishes

The inner ear and other tissues of some fish species, including the rainbow trout (shown here), showed no physiological damage when exposed to intense sounds associated with low-frequency (170-320Hz) and mid-frequency (2.8-3.8 kHz) sonar. Image credit: U.S. Environmental Protection Agency.

There are concerns about the potential effects of the U.S. Navy’s Surveillance Towed Array Sensor System Low Frequency Active (SURTASS LFA) sonar. This system transmits signals of about 60-second duration at frequencies between 100 and 500 Hz. A study was conducted using one element of the actual LFA sonar in a freshwater lake. Five species, rainbow trout, channel catfish, hybrid sunfish, largemouth bass, and yellow perch, were exposed for 324 or 648 seconds at received levels of 193-195 underwater dB (equivalent to SELcum of 215-220 dB re 1 µPa2s, respectively) at frequencies between 170 and 320 Hz [1]Popper, A. N., Halvorsen, M. B., Kane, A., Miller, D. L., Smith, M. E., Song, J., … Wysocki, L. E. (2007). The effects of high-intensity, low-frequency active sonar on rainbow trout. The Journal of the Acoustical Society of America, 122(1), 623–635. https://doi.org/10.1121/1.2735115.[2]Halvorsen, M. B., Zeddies, D. G., Chicoine, D., & Popper, A. N. (2013). Effects of low-frequency naval sonar exposure on three species of fish. The Journal of the Acoustical Society of America, 134(2), EL205–EL210. https://doi.org/10.1121/1.4812818.. Channel catfish and some rainbow trout sustained a hearing loss of 10 to 20 dB immediately after exposure. Some fish recovered within 24 hours. Importantly, no evidence of injury was found in any of the fish, even though the durations of this exposure are likely longer than would occur in the wild[3]Kane, A. S., Song, J., Halvorsen, M. B., Miller, D. L., Salierno, J. D., Wysocki, L. E., … Popper, A. N. (2010). Exposure of fish to high-intensity sonar does not induce acute pathology. Journal of Fish Biology, 76(7), 1825–1840. https://doi.org/10.1111/j.1095-8649.2010.02626.x..

There are also concerns about mid-frequency sonars. Using the same location as described above, channel catfish, rainbow trout, and hybrid sunfish were exposed to mid-frequency active (MFA) sonar signals. In one study, the MFA signal was a repeated 2-second sweep from 2.8 to 3.8 kHz followed by a 1-second, 3.3 kHz tone for a SELcum of 220 dB[4]Halvorsen, M. B., Zeddies, D. G., Ellison, W. T., Chicoine, D. R., & Popper, A. N. (2012). Effects of mid-frequency active sonar on hearing in fish. The Journal of the Acoustical Society of America, 131(1), 599–607. https://doi.org/10.1121/1.3664082.. There was no hearing loss in the rainbow trout nor hybrid sunfish. Some channel catfish experienced a small threshold shift, which recovered within 24 hours. In a second study, there was no hearing loss in channel catfish exposed to mid-frequency signals at maximum received level 210 underwater dB for 15 seconds[5]Kane, A. S., Song, J., Halvorsen, M. B., Miller, D. L., Salierno, J. D., Wysocki, L. E., … Popper, A. N. (2010). Exposure of fish to high-intensity sonar does not induce acute pathology. Journal of Fish Biology, 76(7), 1825–1840. https://doi.org/10.1111/j.1095-8649.2010.02626.x..

In a different study, wild Atlantic herring were exposed to MFA sonar ranging from 1 to 7 kHz, with source levels of 197- 209 dB re 1 µPa at 1 m, and signal durations of 1 second[6]Doksæter, L., Rune Godø, O., Olav Handegard, N., Kvadsheim, P. H., Lam, F.-P. A., Donovan, C., & Miller, P. J. O. (2009). Behavioral responses of herring (Clupea harengus) to 1–2 and 6–7kHz sonar signals and killer whale feeding sounds. The Journal of the Acoustical Society of America, 125(1), 554–564. https://doi.org/10.1121/1.3021301.. Fish movements were tracked with two 38 kHz upward-looking echosounders. No flight responses were detected during the sonar exposures, however fish did respond to playback of killer whale signals in this study. Post-spawning herring, during their westward summer migration, were exposed to the same sonar signals[7]Sivle, L. D., Kvadsheim, P. H., Ainslie, M. A., Solow, A., Handegard, N. O., Nordlund, N., & Lam, F.-P. A. (2012). Impact of naval sonar signals on Atlantic herring (Clupea harengus) during summer feeding. ICES Journal of Marine Science, 69(6), 1078–1085. https://doi.org/10.1093/icesjms/fss080.. Fish schools neither dived nor changed their school density during exposure. Captive herring in an aquaculture pen did not react to sonar signals from a passing frigate at received levels of up to 168 underwater dB[8]Doksæter, L., Handegard, N. O., Godø, O. R., Kvadsheim, P. H., & Nordlund, N. (2012). Behavior of captive herring exposed to naval sonar transmissions (1.0–1.6 kHz) throughout a yearly cycle. The Journal of the Acoustical Society of America, 131(2), 1632–1642. https://doi.org/10.1121/1.3675944..

Potential Effects: Marine Mammals

The graphs show the distribution of humpback whale song length (in minutes) during control periods when no sounds were being played (top) and during experimental conditions when LFA sounds were being played (bottom). The two graphs look similar and show that there is considerable variation in the length of humpback whale songs. The songs were slightly longer during LFA playbacks. Graph from data in Fristrup, K. M., Hatch, L. T., & Clark, C. W. (2003). Variation in humpback whale (Megaptera novaeangliae) song length in relation to low-frequency sound broadcasts. The Journal of the Acoustical Society of America, 113(6), 3411.

Because marine mammals have hearing that ranges from infrasonic to ultrasonic frequencies, sonars may also affect them. Three controlled exposure studies using SURTASS LFA sonar systems investigated the behavioral responses of marine mammals with good low-frequency hearing. The studies focused on blue and fin whales foraging off southern California, gray whales migrating along the California coast, and humpback whales in breeding grounds off Hawaii. Individual whales were followed visually and/or acoustically to document their behavior before, during, and after exposure to the sonar. Blue and fin whale behavior was found to be more influenced by prey location than received sonar signals[9]Croll, D. A., Clark, C. W., Calambokidis, J., Ellison, W. T., & Tershy, B. R. (2001). Effect of anthropogenic low-frequency noise on the foraging ecology of Balaenoptera whales. Animal Conservation, 4(1), 13–27. https://doi.org/10.1017/S1367943001001020.. Gray whales altered their migration path away from the sonar source when it was located in the center of their migration corridor. However, when the sonar was moved to the edge of the migration corridor, the whales did not change direction, even when exposed to similar received levels[10]Buck, J. R., & Tyack, P. L. (2000). Response of gray whales to low‐frequency sounds. The Journal of the Acoustical Society of America, 107(5), 2774–2774. https://doi.org/10.1121/1.428908.[11]Ellison, W. T., Southall, B. L., Clark, C. W., & Frankel, A. S. (2012). A New Context-Based Approach to Assess Marine Mammal Behavioral Responses to Anthropogenic Sounds: Marine Mammal Behavioral Responses to Sound. Conservation Biology, 26(1), 21–28. https://doi.org/10.1111/j.1523-1739.2011.01803.x.. Although there is variation in humpback whale song length, studies with LFA sonar exposure show singing humpback whales increased song length by 29% during sonar transmissions. Songs were 10% longer for up to two hours after sonar transmissions ceased[12]Miller, P. J. O., Biassoni, N., Samuels, A., & Tyack, P. L. (2000). Whale songs lengthen in response to sonar. Nature, 405(6789), 903–903. https://doi.org/10.1038/35016148.[13]Fristrup, K. M., Hatch, L. T., & Clark, C. W. (2003). Variation in humpback whale (Megaptera novaeangliae) song length in relation to low-frequency sound broadcasts. The Journal of the Acoustical Society of America, 113(6), 3411. https://doi.org/10.1121/1.1573637..

Studies have shown that military sonar exercises have contributed to some mass strandings of beaked whales [14]D’Amico, A., Gisiner, R. C., Ketten, D. R., Hammock, J. A., Johnson, C., Tyack, P. L., & Mead, J. (2009). Beaked whale strandings and naval exercises. Aquatic Mammals, 35(4), 452–472. https://doi.org/10.1578/AM.35.4.2009.452.[15]Filadelfo, R., Mintz, J., Michlovich, E., D’Amico, A., Tyack, P. L., & Ketten, D. R. (2009). Correlating military sonar use with beaked whale mass strandings: What do the historical data show? Aquatic Mammals, 35(4), 435–444. https://doi.org/10.1578/AM.35.4.2009.435.[16]National Research Council (U.S.) (Ed.). (2003). Ocean noise and marine mammals. Washington, D.C: National Academies Press.[17]Evans, D. L., & England, G. R. (2001). Joint Interim Report Bahamas Marine Mammal Stranding Event 15-16 March 2000. Washington, D.C.: Department of the Navy and Department of Commerce, National Oceanic and Atmospheric Administration. Retrieved from https://repository.library.noaa.gov/view/noaa/16198/noaa_16198_DS1.pdf.[18]Ketten, D. R. (2014). Sonars and strandings: Are beaked whales the aquatic acoustic canary? Acoustics Today, 10(3), 46–56.. However, it is still not clear if it is the sound of the sonar, the movement of the ships, or other aspects of the military ship exercises, that resulted in the strandings. Given the association of some beaked whale strandings with military sonar exercises, research studies into the behavioral responses of marine mammals to sonars and other sounds have been conducted[19]Southall, B., Nowacek, D., Miller, P., & Tyack, P. (2016). Experimental field studies to measure behavioral responses of cetaceans to sonar. Endangered Species Research, 31, 293–315. https://doi.org/10.3354/esr00764..

Scientists are investigating the behavioral responses of beaked whales and other cetacean species to MFA sonar with a series of controlled exposure studies. In a U.S. Navy range off the Bahamas called the Atlantic Undersea Testing and Evaluation Center (AUTEC), researchers found that beaked whales changed their diving and vocal behavior in response to MFA sonar, as well as other novel stimuli including playbacks of killer whales[20]Allen, A. N., Schanze, J. J., Solow, A. R., & Tyack, P. L. (2014). Analysis of a Blainville’s beaked whale’s movement response to playback of killer whale vocalizations. Marine Mammal Science, 30(1), 154–168. https://doi.org/10.1111/mms.12028.[21]Tyack, P. L., Zimmer, W. M. X., Moretti, D., Southall, B. L., Claridge, D. E., Durban, J. W., … Boyd, I. L. (2011). Beaked whales respond to simulated and actual navy sonar. PLoS ONE, 6(3), e17009. https://doi.org/10.1371/journal.pone.0017009.. Animals stopped vocalizing early in foraging dives, and ascended at a slow, shallow angle away from the sonar. This response was even stronger when animals were exposed to killer whale vocalizations. In other studies, beaked whales left the range area during sonar use, but returned one or more days after the sonar transmissions ended[22]McCarthy, E., Moretti, D., Thomas, L., DiMarzio, N., Morrissey, R., Jarvis, S., … Dilley, A. (2011). Changes in spatial and temporal distribution and vocal behavior of Blainville’s beaked whales (Mesoplodon densirostris) during multiship exercises with mid-frequency sonar. Marine Mammal Science, 27(3), E206–E226. https://doi.org/10.1111/j.1748-7692.2010.00457.x.. Little change was seen in pilot whale vocal behavior, but melon-headed whales were found to produce more sonar-like whistles[23]DeRuiter, S. L., Boyd, I. L., Claridge, D. E., Clark, C. W., Gagnon, C., Southall, B. L., & Tyack, P. L. (2013). Delphinid whistle production and call matching during playback of simulated military sonar. Marine Mammal Science, 29(2), E46–E59. https://doi.org/10.1111/j.1748-7692.2012.00587.x.. Based on observational research of behavioral responses of Blainville’s beaked whales to Navy sonar, scientists developed a risk function that predicts that half of the individuals in the Blainville’s beaked whale population around AUTEC would stop foraging at received level of 150 underwater dB, but that the other half of the population would continue feeding[24]Moretti, D., Thomas, L., Marques, T., Harwood, J., Dilley, A., Neales, B., … Morrissey, R. (2014). A risk function for behavioral disruption of blainville’s beaked whales (Mesoplodon densirostris) from mid-frequency active sonar. PLoS ONE, 9(1), e85064. https://doi.org/10.1371/journal.pone.0085064..

Studies of the responses of killer whales and long-finned pilot whales to two different MFA signals (6-8 kHz and 1-2 kHz) were conducted off the coast of Norway. Killer whales were found to be more sensitive to the 6-8 kHz signals than the 1-2 kHz sonar, though the results were not statistically significant, most likely due to the high amount of variability among and within individuals’ responses[25]Miller, P. J. O., Antunes, R. N., Wensveen, P. J., Samarra, F. I. P., Catarina Alves, A., Tyack, P. L., … Thomas, L. (2014). Dose-response relationships for the onset of avoidance of sonar by free-ranging killer whales. The Journal of the Acoustical Society of America, 135(2), 975–993. https://doi.org/10.1121/1.4861346.. A risk function was developed using the results from both signals in which 50% of the killer whales reacted with an avoidance response at a received level of 142 underwater dB. These signals were recorded at a distance of 3.8 to 4.6 km from the sound source. In contrast, 50% of the pilot whale population was estimated to show avoidance at a sound level of 170 underwater dB, much higher than that for killer whales[26]Antunes, R., Kvadsheim, P. H., Lam, F. P. A., Tyack, P. L., Thomas, L., Wensveen, P. J., & Miller, P. J. O. (2014). High thresholds for avoidance of sonar by free-ranging long-finned pilot whales (<i>Globicephala melas<i/>). Marine Pollution Bulletin, 83(1), 165–180. https://doi.org/10.1016/j.marpolbul.2014.03.056..

The behavioral context of exposure may be just as important as the characteristics of the received signal[27]Ellison, W. T., Southall, B. L., Clark, C. W., & Frankel, A. S. (2012). A New Context-Based Approach to Assess Marine Mammal Behavioral Responses to Anthropogenic Sounds: Marine Mammal Behavioral Responses to Sound. Conservation Biology, 26(1), 21–28. https://doi.org/10.1111/j.1523-1739.2011.01803.x.[28]Goldbogen, J. A., Southall, B. L., DeRuiter, S. L., Calambokidis, J., Friedlaender, A. S., Hazen, E. L., … Tyack, P. L. (2013). Blue whales respond to simulated mid-frequency military sonar. Proceedings of the Royal Society B: Biological Sciences, 280(1765), 20130657–20130657. https://doi.org/10.1098/rspb.2013.0657.. For example, blue whales feeding at deep depths off southern California were shown to be more sensitive to simulated mid-frequency sonar signals than animals feeding at shallower depths or not feeding[29]Goldbogen, J. A., Southall, B. L., DeRuiter, S. L., Calambokidis, J., Friedlaender, A. S., Hazen, E. L., … Tyack, P. L. (2013). Blue whales respond to simulated mid-frequency military sonar. Proceedings of the Royal Society B: Biological Sciences, 280(1765), 20130657–20130657. https://doi.org/10.1098/rspb.2013.0657.. Furthermore, when the prey on which the animals were feeding was measured and included in the analysis, scientists found that blue whales responded more strongly to pseudo-random noise than to mid-frequency sonar signals[30]Friedlaender, A. S., Hazen, E. L., Goldbogen, J. A., Stimpert, A. K., Calambokidis, J., & Southall, B. L. (2016). Prey-mediated behavioral responses of feeding blue whales in controlled sound exposure experiments. Ecological Applications, 26(4), 1075–1085. https://doi.org/10.1002/15-0783..

In summary, there is considerable variability in the probability and the degree of a behavioral response[31]Southall, B., Nowacek, D., Miller, P., & Tyack, P. (2016). Experimental field studies to measure behavioral responses of cetaceans to sonar. Endangered Species Research, 31, 293–315. https://doi.org/10.3354/esr00764.. This appears to be because of individual and species differences in sensitivities to sounds, as well as differences in an animal’s behavioral state when an exposure occurs. The context, such as whether the source is moving towards or away from the animal, as well as the speed at which the source is moving, and whether an animal is motivated to remain in an area, also seem to matter. Despite this variability, received sound levels remain an important component to consider when determining the potential effects of sonars.

Additional Links on DOSITS

References

  • Mann, D. A., Higgs, D. M., Tavolga, W. N., Souza, M. J., & Popper, A. N. (2001). Ultrasound detection by clupeiform fishes. The Journal of the Acoustical Society of America, 109(6), 3048–3054. https://doi.org/10.1121/1.1368406.
  • Popper, A. N., Hawkins, A. D., Fay, R. R., Mann, D., Bartol, S., Carlson, T., … Tavolga, W. N. (2014). Sound exposure guidelines for fishes and sea turtles: ASA S3/SC1.4 TR-2014 ; a technical report prepared by ANSI-accredited Standards Committee S3/SC1 and registered with ANSI.Cham, Switzerland: Springer.

 

Cited References   [ + ]

1. Popper, A. N., Halvorsen, M. B., Kane, A., Miller, D. L., Smith, M. E., Song, J., … Wysocki, L. E. (2007). The effects of high-intensity, low-frequency active sonar on rainbow trout. The Journal of the Acoustical Society of America, 122(1), 623–635. https://doi.org/10.1121/1.2735115.
2. Halvorsen, M. B., Zeddies, D. G., Chicoine, D., & Popper, A. N. (2013). Effects of low-frequency naval sonar exposure on three species of fish. The Journal of the Acoustical Society of America, 134(2), EL205–EL210. https://doi.org/10.1121/1.4812818.
3, 5. Kane, A. S., Song, J., Halvorsen, M. B., Miller, D. L., Salierno, J. D., Wysocki, L. E., … Popper, A. N. (2010). Exposure of fish to high-intensity sonar does not induce acute pathology. Journal of Fish Biology, 76(7), 1825–1840. https://doi.org/10.1111/j.1095-8649.2010.02626.x.
4. Halvorsen, M. B., Zeddies, D. G., Ellison, W. T., Chicoine, D. R., & Popper, A. N. (2012). Effects of mid-frequency active sonar on hearing in fish. The Journal of the Acoustical Society of America, 131(1), 599–607. https://doi.org/10.1121/1.3664082.
6. Doksæter, L., Rune Godø, O., Olav Handegard, N., Kvadsheim, P. H., Lam, F.-P. A., Donovan, C., & Miller, P. J. O. (2009). Behavioral responses of herring (Clupea harengus) to 1–2 and 6–7kHz sonar signals and killer whale feeding sounds. The Journal of the Acoustical Society of America, 125(1), 554–564. https://doi.org/10.1121/1.3021301.
7. Sivle, L. D., Kvadsheim, P. H., Ainslie, M. A., Solow, A., Handegard, N. O., Nordlund, N., & Lam, F.-P. A. (2012). Impact of naval sonar signals on Atlantic herring (Clupea harengus) during summer feeding. ICES Journal of Marine Science, 69(6), 1078–1085. https://doi.org/10.1093/icesjms/fss080.
8. Doksæter, L., Handegard, N. O., Godø, O. R., Kvadsheim, P. H., & Nordlund, N. (2012). Behavior of captive herring exposed to naval sonar transmissions (1.0–1.6 kHz) throughout a yearly cycle. The Journal of the Acoustical Society of America, 131(2), 1632–1642. https://doi.org/10.1121/1.3675944.
9. Croll, D. A., Clark, C. W., Calambokidis, J., Ellison, W. T., & Tershy, B. R. (2001). Effect of anthropogenic low-frequency noise on the foraging ecology of Balaenoptera whales. Animal Conservation, 4(1), 13–27. https://doi.org/10.1017/S1367943001001020.
10. Buck, J. R., & Tyack, P. L. (2000). Response of gray whales to low‐frequency sounds. The Journal of the Acoustical Society of America, 107(5), 2774–2774. https://doi.org/10.1121/1.428908.
11, 27. Ellison, W. T., Southall, B. L., Clark, C. W., & Frankel, A. S. (2012). A New Context-Based Approach to Assess Marine Mammal Behavioral Responses to Anthropogenic Sounds: Marine Mammal Behavioral Responses to Sound. Conservation Biology, 26(1), 21–28. https://doi.org/10.1111/j.1523-1739.2011.01803.x.
12. Miller, P. J. O., Biassoni, N., Samuels, A., & Tyack, P. L. (2000). Whale songs lengthen in response to sonar. Nature, 405(6789), 903–903. https://doi.org/10.1038/35016148.
13. Fristrup, K. M., Hatch, L. T., & Clark, C. W. (2003). Variation in humpback whale (Megaptera novaeangliae) song length in relation to low-frequency sound broadcasts. The Journal of the Acoustical Society of America, 113(6), 3411. https://doi.org/10.1121/1.1573637.
14. D’Amico, A., Gisiner, R. C., Ketten, D. R., Hammock, J. A., Johnson, C., Tyack, P. L., & Mead, J. (2009). Beaked whale strandings and naval exercises. Aquatic Mammals, 35(4), 452–472. https://doi.org/10.1578/AM.35.4.2009.452.
15. Filadelfo, R., Mintz, J., Michlovich, E., D’Amico, A., Tyack, P. L., & Ketten, D. R. (2009). Correlating military sonar use with beaked whale mass strandings: What do the historical data show? Aquatic Mammals, 35(4), 435–444. https://doi.org/10.1578/AM.35.4.2009.435.
16. National Research Council (U.S.) (Ed.). (2003). Ocean noise and marine mammals. Washington, D.C: National Academies Press.
17. Evans, D. L., & England, G. R. (2001). Joint Interim Report Bahamas Marine Mammal Stranding Event 15-16 March 2000. Washington, D.C.: Department of the Navy and Department of Commerce, National Oceanic and Atmospheric Administration. Retrieved from https://repository.library.noaa.gov/view/noaa/16198/noaa_16198_DS1.pdf.
18. Ketten, D. R. (2014). Sonars and strandings: Are beaked whales the aquatic acoustic canary? Acoustics Today, 10(3), 46–56.
19. Southall, B., Nowacek, D., Miller, P., & Tyack, P. (2016). Experimental field studies to measure behavioral responses of cetaceans to sonar. Endangered Species Research, 31, 293–315. https://doi.org/10.3354/esr00764.
20. Allen, A. N., Schanze, J. J., Solow, A. R., & Tyack, P. L. (2014). Analysis of a Blainville’s beaked whale’s movement response to playback of killer whale vocalizations. Marine Mammal Science, 30(1), 154–168. https://doi.org/10.1111/mms.12028.
21. Tyack, P. L., Zimmer, W. M. X., Moretti, D., Southall, B. L., Claridge, D. E., Durban, J. W., … Boyd, I. L. (2011). Beaked whales respond to simulated and actual navy sonar. PLoS ONE, 6(3), e17009. https://doi.org/10.1371/journal.pone.0017009.
22. McCarthy, E., Moretti, D., Thomas, L., DiMarzio, N., Morrissey, R., Jarvis, S., … Dilley, A. (2011). Changes in spatial and temporal distribution and vocal behavior of Blainville’s beaked whales (Mesoplodon densirostris) during multiship exercises with mid-frequency sonar. Marine Mammal Science, 27(3), E206–E226. https://doi.org/10.1111/j.1748-7692.2010.00457.x.
23. DeRuiter, S. L., Boyd, I. L., Claridge, D. E., Clark, C. W., Gagnon, C., Southall, B. L., & Tyack, P. L. (2013). Delphinid whistle production and call matching during playback of simulated military sonar. Marine Mammal Science, 29(2), E46–E59. https://doi.org/10.1111/j.1748-7692.2012.00587.x.
24. Moretti, D., Thomas, L., Marques, T., Harwood, J., Dilley, A., Neales, B., … Morrissey, R. (2014). A risk function for behavioral disruption of blainville’s beaked whales (Mesoplodon densirostris) from mid-frequency active sonar. PLoS ONE, 9(1), e85064. https://doi.org/10.1371/journal.pone.0085064.
25. Miller, P. J. O., Antunes, R. N., Wensveen, P. J., Samarra, F. I. P., Catarina Alves, A., Tyack, P. L., … Thomas, L. (2014). Dose-response relationships for the onset of avoidance of sonar by free-ranging killer whales. The Journal of the Acoustical Society of America, 135(2), 975–993. https://doi.org/10.1121/1.4861346.
26. Antunes, R., Kvadsheim, P. H., Lam, F. P. A., Tyack, P. L., Thomas, L., Wensveen, P. J., & Miller, P. J. O. (2014). High thresholds for avoidance of sonar by free-ranging long-finned pilot whales (<i>Globicephala melas<i/>). Marine Pollution Bulletin, 83(1), 165–180. https://doi.org/10.1016/j.marpolbul.2014.03.056.
28. Goldbogen, J. A., Southall, B. L., DeRuiter, S. L., Calambokidis, J., Friedlaender, A. S., Hazen, E. L., … Tyack, P. L. (2013). Blue whales respond to simulated mid-frequency military sonar. Proceedings of the Royal Society B: Biological Sciences, 280(1765), 20130657–20130657. https://doi.org/10.1098/rspb.2013.0657.
29. Goldbogen, J. A., Southall, B. L., DeRuiter, S. L., Calambokidis, J., Friedlaender, A. S., Hazen, E. L., … Tyack, P. L. (2013). Blue whales respond to simulated mid-frequency military sonar. Proceedings of the Royal Society B: Biological Sciences, 280(1765), 20130657–20130657. https://doi.org/10.1098/rspb.2013.0657.
30. Friedlaender, A. S., Hazen, E. L., Goldbogen, J. A., Stimpert, A. K., Calambokidis, J., & Southall, B. L. (2016). Prey-mediated behavioral responses of feeding blue whales in controlled sound exposure experiments. Ecological Applications, 26(4), 1075–1085. https://doi.org/10.1002/15-0783.
31. Southall, B., Nowacek, D., Miller, P., & Tyack, P. (2016). Experimental field studies to measure behavioral responses of cetaceans to sonar. Endangered Species Research, 31, 293–315. https://doi.org/10.3354/esr00764.