Abstract

In recent years, scientists have noticed a trend between the use of sonar and the injuries or death of marine wildlife. Further studies in this field have shown that sonar does indeed have the potential to affect marine wildlife, such as whales, in ways ranging from changes in behavior, to behavior that endangers the health and life of the animals, to direct injury of the animals from the sounds themselves. These effects are widespread and well-documented, and continue despite there being ways to, at the very least, reduce the destructive impact of the sonar. For these reasons, this use of sonar is in contravention of the Marine Mammal Protection Act, and should be discontinued.

The story

In 2003, Ken Balcomb, a research biologist, noticed some unusual behavior in a pod of orcas near Puget Sound. (Pickrell). The killer whales, which seemed to be agitated, were moving in an unusually tight formation very close to the shore. Further study of the area showed an "above-average number of seemingly healthy porpoises ... stranded on nearby beaches" (Pickrell). Balcomb concluded that these aberrant behaviors by the local marine wildlife was due to sonar being used a Navy frigate at the time. Although this sonar was audible to microphones in the water at a distance of twelve miles, the frigate moved to within four miles of Puget Sound (Pickrell).

Although Balcomb is one of the most vocal scientists who believe that sonar is dangerous to marine mammals, he is by no means the only one. The reasoning is sound, in more ways than one. Many marine mammals use their own sonar for the purposes of finding food or communicating with their own kind, and it might seem that the artificial sonar generated by ships could interfere with that, causing problems with these abilities. However, studies have shown that the truth is much worse than that. Much as we would wish to get away from loud, painful noises, sonar can interrupt the normal behavior of marine mammals, and induce them to do anything they can to escape from the source, including dangerous behavior such as beaching themselves. As Balcomb is quoted as saying in Pickrell's article, in describing the orcas unusual movements and actions, "It's like they where[sic] searching for some way out of the sound field." Even worse, some studies have shown that the sonar can cause direct injury to the animals themselves just from the power of the sound waves, regardless of the animals' reactions.

The studies

To begin with, studies have shown a clear pattern of avoidance. One study used a recording of low-frequency sonar sounds to measure their effects on humpback whales, in the area of Hawaii(Maybaum). The results of this study were that, consistently, the whales would move away from the source of the sonar sounds, a reaction that would increase as time went on. The article discussing the study notes that part of this reaction may be due to a similarity between the sonar sounds and the "natural sounds in humpbacks' environment that are associated with biological threats or warnings." Similar studies on bowhead whales revealed a similar pattern of avoidance, with similar pulse sounds in the 150-180 dB range (Richardson and Greene).
However, the danger of sonar is not merely limited to changing patterns of travel. The rapid movements resultant from sonar can induce decompression sickness in whales, and scans of some bodies of whales found beached after a sonar exercise revealed "hemorrhaging around the brain and ears"(Pickrell). Studies have shown that the damage done to whales by sonar is not limited to indirect damage. In a letter to the US Navy, Balcomb once again speaks on behalf of the whales, outlining the damage that can be done by sonar.

"The killing is largely due to resonance phenomena in the whales cranial airspaces that are tearing apart delicate tissues around the brains and ears. This is an entirely separate issue from auditory thresholds and traumas that the Navy has fixated upon. In my earlier comments, I questioned whether there might be a problem with injurious resonance phenomena created by the sonar system described in your OEIS/EIS; but, now I have seen the problem and can attest to the fact that there is massive injury to whales caused by sonar."
Balcomb's letter goes on to explain that the resonance frequency of the inside of a whale's head (specifically, he uses the example of the Cuvier beaked whale) is almost identical to the frequency used by naval sonar exercises. Since resonance frequencies are the same phenomenon that, most famously, causes wine glasses to shatter when exposed to a specific frequency of sound, Balcomb's letter expresses great distress that whales are being exposed to this specific frequency of sound, citing an array of resultant problems ranging from vertigo to tissue tearing and hemorrhaging. In case his math is doubted, Balcomb also describes how his findings match the results of necropsies performed on whales that had been beached in the aftermath of sonar exercises in the Bahamas.

A possible solution

Another expert, specifically one in marine mammal acoustics, has proposed a fairly simple idea that, while not perfect, has potential to greatly reduce the injury caused to whales by sonar. Roger Gentry is an expert in marine mammal acoustics, and has provided the Navy with a map of global whale "hot spots" to avoid using sonar in, such as marine canyons, which are unfortunately a good spot for both whales and submarines to hide in (Pickrell). The idea here is a compromise, where sonar could be used only in areas where whales are minimally present. Of course, there are several problems with this idea, starting with the fact that enemy submarines are unlikely to avoid areas populated by whales. The fact is that modern warfare seems to necessitate sonar use in areas dangerous to marine wildlife, such as near dangerous shores, or areas of high whale population.

Conclusions

The ways in which sonar is dangerous to whales are well-documented. There are indirect methods of damage to whales, such as causing them to change their behavior to avoid the sounds. This can result in disorientation of the whales, decompression sickness (or "the bends") from moving too quickly to escape the sounds of the sonar, or beaching themselves on land, which frequently results in death.
The damage can also be direct. Whether it's from being harmonic with the inside of their heads, or from being simply far too loud, the sounds of sonar can cause tissue damage inside a whale's head or lungs, or hemorrhaging of these same tissues or the brain. Any of these can also result in death for the whale it is inflicted upon, and even if not death, pain and impairment of function.
The Marine Mammal Protection Act is exactly what is sounds like - a legal act which protects marine mammals. It states:

"Marine mammals have proven themselves to be resources of great international significance, esthetic and recreational as well as economic, and it is the sense of the Congress that they should be protected and encouraged to develop to the greatest extent feasible commensurate with sound policies of resource management and that the primary objective of their management should be to maintain the health and stability of the marine ecosystem."

To this end, the Marine Mammal Protection Act prohibits the "taking" of marine mammals. In this context, "take" is a legal term, meaning to "harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or kill any marine mammal." The evidence, provided by the studies described above, clearly shows that sonar has the means to harass marine mammals, by driving them away from their normal migratory routes, and possibly even to their deaths. The Marine Mammal Protection Act was clearly created to prevent exactly this kind of damage to marine wildlife, and there should be no exception to this rule granted to the military so that they can continue to use their destructive sonar without regard for the harm it does to the environment.