Weilgart, L.

Whitehead, H.

English

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Polarforschung 72 (2/3), 99 - 101, 2002 (erschienen 2004)The Threat ofUnderwater Noise on Whales:Management in Light of Scientific Limitationsby Linda Weilgart' and Hai Whitehead'There is no longer any question that noise can significantlyimpact individual marine mammals, even to the point of kill-ing them (BALCOMB & CLARIDGE 2001, NATIONAL MARINEFISHERIES SERVICE & UNITED STATES NAVY 2001). The dif-ficult question before us now is: does noise affect the health ofpopulations and of ecosystems? This is an important issue thatseems often forgotten in our efforts to gather more data onindividual reactions. So, noise can affect anatomy (hearingloss), physiology (it can theoretically trigger "the bends";HOUSER et al. 2001), behaviour (change in dive pattern), andpsychology (stress, avoidance of areas which were previouslyloud). Ifwe are concerned about animal welfare, then all thesecould have impacts on the welfare of an animal. If we areconcerned about populations, then all these factors couldaffect the population of a focal species, but in addition, theycould affect the populations of other species. If the focal spe-cies changes its behaviour relative to predators 01' prey, thenthat impacts other species as well. lf we are concerned aboutecosystems, then these impacts on the populations of severalspecies could affect ecosystem function. These first effects fallunder the area of population biology, and the second ones arein the area of community ecology. And yet, only the anatomy,physiology, and behaviour - mainly behaviour - of individualsexposed to noise have been studied up to this point. If oneconsiders the picture portrayed above, one can see how manyinterrelationships and links are already present, and thenremember that this only represents one focal species. If oneconsiders more species, the picture gets vastly more complex.The problems we are facing, then, in trying to study the ef-fects of noise on whales in the open ocean are: there are toomany potential links in the ecosystem, marine populationbiology is very hard to study and is very imprecise (for mostwhale and dolphin species we can only estimate populationsizes within 40 %, so populations could be 40 % larger 01'smaller than we have estimated; WHlTEHEAD et al. 2000),marine community ecology is especially hard to study as fewrelationships between species have been clearly established(how does one species' population size affect another's?), thespatial scales are huge in the ocean, the natural variation inmarine ecosystems is huge, the maximum rates of increase ofsome species are very low (ca. 1 % per year for Sperm Whales;WHITEHEAD (in press) so we are looking for very smalI,but potentially profound, effects; and the logistics of Depart-ment of Biology, Dalhousie University, Halifax, Nova Scotia,Canada studying animals in the open ocean are very difficult.Added to these problems are the difficulties in studying theeffects of noise, in particular: hearing damage is hard toassess, especially in the great whales (few audiograms exist);, Department of Biology, Dalhousic University, Halifax, Nova Scotia, Canadathose characteristics of noise which make it disturbing arehard to define, even for humans, there is great variability insensitivity to noise between individuals, between species,between age c1asses (mother-calf pairs tend to be most sensi-tive), between sexes (males sometimes approach noisesources, perhaps because they perceive noise as aggressive 01'a threat display), and reactions 01' sensitivity to noise candepend greatly on the activity the whales are engaged in(RICHARDSON et al. 1995). Resting animals often avoid noise,whereas foraging animals often ignore noise, i.e. they may be"putting up with" noise because the food is there (RICHARDSONet al. 1995). And finally, it is difficult to determine whicheffects ofnoise on cetaceans really are biologically significant,i.e. will they significantly impact the population?This is why, to date, it is practically impossible to predict whatthe impacts of a certain type of noise will be, and which typesof noise will be dangerous to which animals under whichcircumstances. A major obstacle is the fact that the short-termeffects of noise are not necessarily Iinked to the long-termimpacts. For instance, if there are changes in dive pattern thisdoes not mean that such a short-term effect would impact thepopulation over the long-term. Conversely, even if there are noobservable changes in short-term behaviour, there could stillbe severe impacts on the population. Humpback Whales offNewfoundland exposed to explosions showed little behav-ioural reaction to the noise (no decreased residency, no changein overall movements, no change in general behaviour; TODDet al. 1996). However, it soon became evident that theseHumpback Whales had a higher incidence than elsewhere inNewfoundland of becoming entangled in fishing gear anddying. The whales may have become hearing impaired andthus, did not detect the presence ofthe nets as well (TODD et al.1996). Were it not for the unique situation of a) Humpbacksbecoming entangled in fishing gear and b) the knowledge ofwhat "normal" entanglement rates are, this Iikely harmfuleffect of the explosions would have gone unnoticed, as doundoubtedly hundreds of other such effects. Caribou exposedto low-level jet fighter overflights exhibited a startle reflex,causing them to run for a few seconds. This effect seemedmild and short-terrn. However, analysis showed that the moreexposure a female caribou had to jet overflights, the less Iikelyher calfwas to survive (HARRINGTON & VEITCH 1992). Here, amild, short-terrn reaction was shown to have serious conse-quences for the population.So, short-term effects are not easily linked to long-term im-pacts. Yet, it is the long-term changes in populations 01' po-pulation measures (Iike birth, death, and growth rates) that arethe most important. These are the effects we should beconcerned about, as they are measures of the well-being of a99population. Unfortunately, these very effects are undetectablefor most cetaceans.We have tried to come up with a very incomplete list of thesorts of effects on free-ranging cetaceans that we can detectand the ones we cannot detect, unless they are very dramatic.These detectable effects are only short-term ones on individ-uals, rather than on populations. Detectable effects include:respiration rate, swim speed, vocalizations, dive times, divedepth, residence times, distribution, movement relative tosound source, heart rate. Non-detectable effects (unless dra-matic) include: birth rate (miscarriage rate, pregnancy rate,birth defects, mating rate, rate of finding mates, lactation rate,changes in mating dynamics), death rate (injury, disease,morbidity; vulnerability to hazards like shipping, fishingnets, predators), growth rate, change in echolocation ability asin ability to process echoes, change in group bonds and coor-dination, change in mother-calf bonds or maternal behaviour;annoyance, pain, panic, confusion, anxiety, etc.; change inmemory, learning ability, cognitive functions; change in navi-gational ability; stress; change in aggressiveness; changes inimmune response; changes in metabolic rate; deafness andhearing impairment; effects on contractile forces of musc1es;hyperthermia; effects on vibrotactile system; vestibular/centralnervous system effects; change in susceptibility to the"bends"; change in predator-prey interactions; change inecosystem balance; cumulative noise effects. Some of theseresponses we have taken from a table entitled "Possible Effectsof Exposure to Low Frequency Acoustics" published under"Exposure Guidelines for Navy Divers" (DEPARTMENT OF THENAVY 2001).Another problem is that it is easy to misinterpret the few ef-fects we can observe. For instance, if more whales are seen atthe surface during noise exposure trials, it could mean thatthey are attracted to the noise 01' that they are trying to avoid it,since sound levels can be much reduced at the surface (RICH-ARDSON et al. 1995).One aspect of noise that can make it so potentially destructiveis the huge spatial scale over which loud sounds can be heard.Seismic activity off Nova Scotia is prominent in the acousticbackground off the Bahamas, and along the mid-AtlanticRidge, several thousands of kilometres away (NATIONALMARINE FISHERIES SERVICE & UNITED STATES NAVY 2001,CLARK 2002). Seismic noise can still reach levels of 110 dB re1 ,uPa at a distance of 1,000 km (BOWLES et al. 1994). LowFrequency Active Sonar (LFA), a new type of sonar developedby the U.S. Navy to detect newer, quieter enemy submarines,only drops to a level of 120 dB at a distance of around 500 kmfrom the source (I Potter, pers. comm.). Several marinespecies, not just whales, try to avoid sound at an averagereceived level of 120 dB, so this could mean that marine lifeover an area of 800,000 km 2 are impacted during every broad-cast of LFA sonar. LFA sonar was in use off the coast ofGreece in 1996 as 12 Beaked Whales stranded and died. Thecorrelation in time and space between the ship's movementsand the strandings was very strong, so LFA sonar is suspectedof causing this stranding (FRANTZIS 1998). In March of 2000,this tragedy was repeated off the Bahamas Islands (BALCOMB& CLARIDGE 2001, NATIONAL MARINE FISHERIES SERVICE &UNITED STATES NAVY 2001).17 whales ofat least four species,but mostly Beaked Whales, stranded and at least seven died.100Necropsies showed hemorrhages around the ears and brain,and these injuries were consistent with an intense, acousticevent as opposed to a nearby explosion. In this case, the U.S.Navy admitted that its tactical mid-range sonar was the mostplausible source ofthe stranding (NATIONAL MARINE FISHERIESSERVICE & UNITED STATES NAVY 2001). And while we haveheard much of the anatomical injuries, there has been compa-ratively little talk of the most devastating aspect of this inci-dent, namely that the local population of Cuvier's BeakedWhales was probably destroyed, or at the very least, seriouslydisplaced. None of the known animals that had been studiedover the past nine years has been re-sighted since the strandingevent (BALCOMB & CLARIDGE 2001). Here, we have a veryclear population-level effect, one that no one predicted.And how common are these multi-species strandings? Be-tween 1838 and 1974, there were no multi-species strandingsin which at least one beaked whale species was involved. Butfrom 1974 to 2001, a total of seven multi-species strandingswere documented involving at least one beaked whale spe-cies. In all seven of these cases, naval man euvers were con-ducted nearby (BALCOMB & CLARIDGE 2001).So there is no longer any question that sound can be deadly tocetaceans in ways no one predicted. And while the navalsonars may have very different characteristics from the sei-entific acoustic sources used in the Antarctic, there are alsosufficient and overlapping similarities in intensity, frequency,duration, etc. It remains to be proven which characteristics ofnoise make it dangerous. Until such time as this is definitivelydetermined, prudence and precaution demand that we treat allloud, far-ranging noise sources as potentially dangerous asweIl. Moreover, Antarctica presents special problems as manymarine mammal species are dependent on this fragile, uniqueecosystem for their survival. Beaked Whales, which may beparticularly sensitive to noise, number among its inhabitants.As the deep sound channel is at or near the surface in polarwaters, transmission loss in surface waters, which arefrequented by more marine mammals, will be less, and thus,the effects of noise could be more far-ranging and severe(RICHARDSON et al. 1995).Because of all the problems mentioned earlier, it is our beliefthat the question: "What is the effect of undersea noise oncetaceans?" will remain, for all intents and purposes, unan-swerable. The question: "How can we make undersea noiseless harmful?" is answerable, though. Here, we don't need tohave a perfect understanding of all the fundamental processes(physiological, behavioural, etc.) which are involved in theeffects of noise on cetaceans. Instead, we can look at the rangeof possible outcomes of our actions and make rational deci-sions on how to reduce bad outcomes. This falls under thecategory of science relating to risk reduction in the face ofuncertainty (LUDWIG et al. 1993).We propose the following process to consider noisy projectsthat may provide benefits yet pose large-scale environmentalrisks:(1) Justify project. Strong justification for the need and bene-fit could be required for any project that is potentially devas-tating to the environment. It would be helpful if proponentsmade a convincing case that there are no adequate, more be-nign alternatives. Only if the project can be well justified,might one proceed to the next steps.(2) One could design the project to minimize harm. This couldbe done by:a) avoiding marine Iife either spatially or temporally. In thecase of seismic work in the Antarctic, it may be difficult tospatially avoid concentrations of marine mammals but perhapsone could find a season where fewer marine mammals arepresent.b) reducing the impact of the noise would be beneficial, forinstance by making it quieter.c) avoiding duplication by sharing results of tests when-everpossible.d) avoiding the use of mid-range frequencies Iike I-10kHz,preferably using extrernely low frequencies (1-2 Hz 01' below)01' high frequencies (over 200 kHz).e) turning sounds off when animals are detected, visually 01'acoustically. It should be recognized that this sort ofmitigationis better than nothing, but won't really prevent the exposure ofa large proportion of cetaceans to noise, as there will alwaysbe cetaceans that aren 't visible 01' audible, especially overlarger ranges.f) avoiding new sources of noise.After designing a project to minimize harm, it would be usefulifproponents would:3) Provide funds to an independent agency to sponsor non-aligned research on the effects of sounds on marine Iife. It isbest if marine mammaI scientists don 't have close ties to theirpaymasters, the noise polluters. The perception of bias is asdamaging to the science and credibility ofthe scientists as truebias (WHITEHEAD & WEILGART 1995). An independentcommittee which has power could establish priorities for theresearch, commission it, and recommend regulations.At present, the U.S. Navy provides the majority of funds formarine mammal research in the world (Vice Admiral Dennis VMcGinn, Testimony to US House of Representatives,Committee on Resources, II October 200 I), which, given thatthe U.S. Navy is one of the worst acoustic polluters, is aconflict-of-interest situation.We have focused on some of the limitations of studies ofshort-terrn, individual, reactions to noise. Probably the mostuseful are studies correlating changes in the acoustic envi-ronment with occurrences such as strandings, as was donewith naval activities and strandings. Long-term studies relat-ing long-terrn effects on population size with changes in noiselevels would help improve our understanding of the effects ofnoise on whale populations over the long term.In conclusion, underwater noise is dangerous but the mostimportant consequences cannot now be determined; levelsshould be reduced, distanced from marine Iife and new noisesources avoided; major polluters should not directly fund theresearch; and finally, in deciding whether environmentally-risky projects should proceed, the more prudent course ofaction follows the Precautionary Principle, where measuresare taken to prevent harm even in the absence of conclusivescientific evidence.ReferencesBalcomb, K. C & Claridge, DE. (200 I): A mass slranding of cetaeeanseaused by naval sonar inthe Bahamas. Bahamas.- Journ, Sei. 5: 2-12.Bowles, A.E., Smultea, M., Würsig, B., DeMaster; DP & Palka, D (1994):Relative abundanee and behavior of marine mammals exposed to trans-missions from the Heard Island Feasibility Test.- Journ. Aeoustical Soc.Amer, 96: 2469-2484.Clark, C W (2002): Statement to the Pub1ic Review Commission on Hydro-carbon Exploration offCape Breton. Nova Scotia, Canada.Department of the Navy (2001): Final Overseas Environmental Impact State-ment anc1 Environmental Impact Statement for Surveillanee Towed SensorSystem Low Frequency Aetive (SURTASS LFA) Sonar. Department ofNavy, Arlington, VA, USA.Frantzis, A. (1998): Does aeoustic testing strand whales?- Nature 392: 29.Harrington, FH. & Veitch,A.M. (1992): Calving snceess ofwood1and earibouexposed tolow-level jet fighter overflights.- Arctie 45: 213-218.Houser, DS. Howard, R. & Ridgway, S (2001): Can diving-induced tissuenitrogen supersaturation increase thc chance ofacoustically driven bubblegrowth inmarine mammals?- Journ. Thear. Biol. 213: 183-195.Ludwig, D, Hilborn, R. & Walters, C. (1993): Uncertainty, resource explo-ration, and eonservation: lessons frorn history.- Scienee 260: 17,36.National Marine Fisheries Service & United States Navv (2001): Joint inter-im report. Bahamas marine mammal mass stranding event 15-16 March2000.Richardson, WJ, Greene, CR., Malme, Cl. & Thomson, DH. (1995): Marinemamrnals and noise.- San Diego: Acadernic Press.Todd, S, Stevick, P, Lien, J, Marques, F & Ketten., D (1996): Behaviouraleffeets to underwater explosions in Humpback Whales (Megapteranovaeangliae)> Can. Journ. Zoo!. 74: 1661-1672.Whitehead, H (in press): Estimates of the eurrent global population size andhistorical trajeetory for sperrn whales.- Mal'. Eeo!. Progr. Ser.Whitehead, 11. & Weilgart. L. (1995): Marine mammal science, the U.S. Navyand aeademie freedom.- Mar. Mamma! Sei. 11: 260-263.Whitehead, H, Reeves, R.R. & Tyack, PL. (2000): Seience and the conser-vation, protection, and management of wild eetaceans.- In: 1. MANN,R.C. CONNOR, PL. TYACK & H. WHITEHEAD (eds.). Cetaceansocieties. Chieago Univertsity Press, Chicago, IL, 308-332.101

The Threat of Underwater Noise on Whales: Management in Light of Scientific Limitations

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