Effect of Underwater Acoustics on Whales
Whales utilize acoustic frequencies to communicate underwater. If the whales are unable to communicate their bi-annual migration can become perilous. Man-made low frequency sonar can prevent whales from producing sound and sometimes causes them to take alternate routes. When the whales try to avoid the sonar they are in danger of running ashore and perishing after being beached.
Twice a year, around the months of December and May, populations of gray whales migrate from Mexico to Alaska. (Unknown1, 2002) During this journey, they pass the state of California, where acoustical pulses, generated by air guns or water guns, are used in seismic surveys. If the seismic-generated sound waves exceed the “background” noise or normal amount of noise, they could interfere with gray whale communication or disturb behavior. (Unknown1, 2002) It is possible that seismic surveys have a detrimental impact on marine life, such as gray whales.
Whales are able to perceive sound in a wide range of frequencies from 75 Hz up to 150 Hz. In experimental conditions, where the environment’s level of noise is controlled, the whales are more sensitive and hear from 10 Hz to 100 Hz. In addition, smaller whales have a broader range from which they can hear from 10 up to 300Hz. (Unknown2, 2002)
Whales depend on sound for communication, navigation, and even detection of predators and prey. The seismic-generated sound waves may disturb critical abilities. Disruption of any of their vital functions can significantly disturb the fitness of whales. (Unknown3) There are many factors that affect the communication abilities of the whales. Temperature and pressure variations found at the varying depths of the oceans can act as voice tubes and channel whale calls further than usual, which allows for whales on the other side of the ocean to hear the calls. It is in such a fashion that pods may keep in communication with one another. Whales travel in pods. The pods can be compared to schools of fish. Many other whales also use infrasound to communicate, whether it is used as a method to attract mates, warn rivals, communicate between the individuals of their own pods or of another pod, or to find food. (Gerrow, E. 2002) Infrasound is wave phenomenon sharing the physical nature of sound but with a range of frequencies below that of human hearing. The marine acoustics affect the whales such that the migration patterns are altered.
Marine acoustics are an extraordinarily technological matter. There is no way to compare the noise levels in air and the noise levels in the sea, because the standard reference pressures used underwater and air are not the same. Measuring the decibels (dB) used to quantify underwater sounds cannot be used to determine the measure of air sounds. (Unknown5, 2003) However when attempts are made to compare the different levels of sound, there is a noticeable difference of decibels underwater and in the air. The differences are noted in the chart in the results section, titled “Chart of Comparable Airborne and Underwater Noise Sources.” (Horne, J.K. 2000) Large amounts of noise pollution exist under the water surface. Sound, especially low frequency wavelengths, travels very well in water and loud noises could have serious impacts upon the whales. For example, blue whales use high-pitched ultrasonic wavelengths for communication, particularly during migration. (Gerrow E. 2002)
Scientific literature consistently states that whales emigrate from sounds at 115-120 dB. (Richardson, W.J. etc. 1995) Horne’s chart also supports that idea; it claims that avoidance behavior is noticed in various whales between 116-121 dB. In controlled experiments, gray whales have exhibited startled responses, avoidance reactions, and other behavioral changes when exposed to seismic pulses at sound levels corresponding to a distance of 2 to 3 miles from an air gun setup off the California coast. Although Gray whales seem to ignore most low-amplitude vessel sounds, avoidance and approach responses have been observed in field studies. (Unknown1, 2002) Noise pollution such as navy sonar produces large amounts of infrasound causing whales to beach themselves. (Gerrow E. 2002)
Sonar is a general term applied to equipment and associated software that receives and possibly transmits sound. Generic sonar samples the water by sending short single or repetitive pulses of sound from a point source down into the water, up from the bottom or across a body of water. (Horne, J.K. 2000)
One of the most recognized underwater sounds that have a significant effect on whales is Low Frequency Active Sonar (LFAS). LFAS is an under water military system that the U.S. Navy created to detect “quiet” submarines. The LFAS involves projecting an extremely loud low frequency sound into the ocean and then listening for the echoes. This sound is produced at incredibly powerful levels making sound waves travel greater distances in the ocean. This sonar is operated at 230 to 240+ dB. (Unknown4, 2001)
In 1998, many legal cases against the use of LFAS were brought to public attention. Some examples are Humpback whale calves separated from their mothers and a snorkeler was exposed to the LFAS and hospitalized as an acute trauma patient. (Unknown 4, 2001) The Navy terminated the LFAS tests and convinced the judge to dismiss the remaining cases because the research was complete. In 2000, a permit was given to a doctor by the name of Dr. Peter Tyack to conduct more research on LFA that permitted him to harm the whales to a higher degree than cases from 1998. The Federal Notice of the Tyack permit application requested permission to harass various species of cetaceans in the North Atlantic and Mediterranean Sea by subjecting them to harmful amounts of LFA. Some of the researchers in the new study were also members of the LFAS research. The Tyack Permit allowed research done at any frequency that Dr. Tyack chose. (Sinkin, 2001)
The bulk of the research was conducted at Pennsylvania State University on Abington-Ogontz campus at the Library located in the Woodland Building. Many search engines were used to find experiments and researchers in this particular field of ecology and acoustics. Pro-Quest, one of the search engines was used because of its ability to search all periodicals simultaneously such as magazines, newspapers and journals. The following search engines found the background information about LFAS and other facts: Yahoo, Lycos, Go.com and ask.com. The data was collected then carefully screened and reviewed to decide on the value of the information.
Several studies show that gray whales begin to avoid sounds at exposure levels of 110 dB and more than 80% of the whales showed avoidance to sounds at 130 dB. Ninety percent of the whales avoided air gun pulses at 180 dB. As a result, whales slowed down and moved around the sound source. At times, they moved into the shallow surf zone to avoid the noise, respiration rates increased and there were indications that mother-calf pairs were more sensitive to the noise than other whales. (Malme C.I. etc. 1989)
In “Underwater Noise Pollution and its Significance for Whales and Dolphins”, Jonathan Gordon and Anna Moscrop state that shock waves caused by intense underwater sound sources can cause direct tissue damage. Animals with air filled lungs and swim bladders are especially vulnerable because of the large difference in impedance between air in the lungs and their body tissues or seawater. Submerged animals exposed to explosions at short range showed hemorrhage in the lungs and ulceration of the gastro-intestinal tract. (Simmonds, M.P. 1996)
Alexandros Frantzis linked a stranding of Cuvier’s beaked whales in the Mediterranean to military low frequency active (LFA) sonar trials. Cuvier’s beaked whales rarely strand. A Bioacoustics Panel investigated this stranding and it is clear that the NATO vessel transmitting the LFA sonar came within 10 km of the beach where the whales stranded. The panel concluded these whales were exposed to LFA sonar at 150-160 dB (Frantzis, A. 1998). Figure1 shows the range of the LFA titled, “A Schematic of the Propagation of Sound in Convergence Zones” (Unknown6, 2002). Animals in unspecified migration corridors and open ocean concentrations are adequately protected by the tripartite migration protocols (Unknown6, 2002).
Marine acoustics affect whales such that their migration patterns are altered. There are many occurrences when whales try to evade loud sounds, get beached, and are unable to swim back to the ocean. Although most studies have revealed behavioral changes whose long-term significance is difficult to assess, there are clear indications of changed behavior, including some cases in which animals have abandoned critical habitats. In a report submitted to National Marine Fisheries Service in March 1998, on the impact of engine noise on the Hawaiian humpback whale, researchers at the Ocean Mammal Institute found that whales swim 2 to 3 times faster away from engines of 120 dB than they do around quieter engines. Research by the Ocean Mammal Institute also shows that the presence of a boat up to 1/2 mile away significantly changes the behavior of humpback whales. (Unknown3)
The challenges in conducting research on the effect of sonar on whales include obtaining detailed behavioral observations of animals that spend 10-20% of their time submerged, out of sight. Another is the diverse behavioral repertoire of marine mammals, and the difficulty of predicting what animals will do under undisturbed conditions. (Unknown3) Even though Navy or other government groups did most of the studies done on this particular subject, there were no journals that were able to publish the studies done by the Navy.
Whales have been on this planet for a long time. One would believe that they would be able to adapt to the noise made my humans but they can’t their ears are made to be able to hear other whales across the vast ocean. Human noise is so destructive. The Navy and the LFAS is unfortunate. They clearly have no respect for fauna of the sea and are willing to put them in danger to further advance the Navy. Whales live on communication and if they lose the ability to communicate, they will not migrate normally and die as a result.