Effects of noise on cetaceans

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* Objectives

* Bioacoustics

* Noise pollution

* Effects of marine traffic on cetaceans

* Effects of earthquakes on cetaceans

* The effects of sonar on cetaceans

* Effects on cetaceans LFAS

* Conclusions

* Bibliography


Cetaceans are an order of marine mammals spread across the globe: dolphins, whales, porpoises and whales, using bioacoustics primarily for communication and echolocation, human activities such as fishing, chemical pollution, global warming and noise pollution affecting negatively cetaceans.

There have been numerous reports of displacement, damage to the auditory system, stranding or death of cetaceans marine traffic product, tourism, seismic and sonar, mainly low frequency. Many species are classified as globally vulnerable, threatened and endangered species.

To minimize these effects to be created aquatic protected areas and international standards for all these human activities. Only the study and legislation will ensure the perpetuation of these species.

Keywords: underwater acoustics, bioacoustics, cetaceans, and noise pollution.


There are very few indicators of the health of our oceans better than the conservation status of marine mammal populations. These are spread over all the seas and oceans have long life cycles are integrated in complex social groups and placed in higher positions in the marine food web, so concentrate pollutants are exposed to organisms pathogens and to visualize many of the interactions between the ocean and the organisms that inhabit it (Lopez et al, 2003).

Cetaceans are an order of mammals made by dolphins, whales, porpoises and whales which are spread over the waters around the world, from the tropics to the poles. Are about 80 described species of cetaceans worldwide (DELPHIS, 2004). Fully adapted to aquatic life, have front limbs as wings, the atrophied after forming a tail fin and dorsal fin (Gomez, 1963).

They are medium sized or very large, usually spindle-shaped body, elongated head, often pointed, attached directly to the neck (neck region), some with a fleshy dorsal fin, no hind limbs long tail completed in two transverse fleshy lobes broad and notched in the midline, when they have teeth they are equal, lack of enamel; nostrils on top of the head, tiny ear openings, body surface smooth, except a few hairs on the snout; without glands in the skin except the breast and conjunctiva, a thick layer of fat under the skin which provides insulation, stomach complicated oceanic distribution throughout the world is always in the water, if you drag them to die of broken land internal organs, the whales can dive to about 1200 m and can remain submerged for many minutes without breathing, to return to the surface of the lungs expel warm, moist air, which is a supplier when warm air is condensed with colder air of the ocean to mate and breed in the sea, the young are large at birth and are breastfeeding (Storer et al, 1980).

This is one of the lesser-known orders of mammals in Venezuela, the records are scarce and local studies are generally incomplete and timely. Venezuela have been reported for 31 species of cetaceans, which corresponds to 40% of the diversity of this group worldwide, 20 species have already been confirmed in Venezuelan territorial waters, which is a relatively high because most the coast of Venezuela are confined to the Caribbean. All species have been identified as threatened with extinction according to international agency (Romero et al, 1991, Romero and Agudo, 1993).

The order Cetacea is divided into three sub orders, the group represented by zenglodontos Archaeoceti extinct, distributed between the Eocene to the Oligocene odontoceti group that includes all those who are provided with teeth, 2 to 40 teeth depending on the species, an opening nasal, and predators are carnivorous habits, represented by dolphins, whales and orcas, and the sub Mysticeti order covering all those who instead of teeth have many parallel horny plates called baleen whales in the sides or upper jaw, which used to filter the masses of small crustaceans and fish they eat, have two nostrils, these are the great whales. (Gomez, 1963, Storer et al, 1980; Bola~nos and Boher 1996).

Over seventy million years of adaptation to the marine environment, cetaceans have developed the necessary changes to use sound waves in the salt waters are an ideal medium for propagation. The cetacean bioacoustics studies have shown aspects as striking as the songs of the humpback, whistles the orcas communication, the use of low frequency waves by dolphins to navigate and communicate at transoceanic or even the use of wave sound by various odontocetes as a weapon to stun or kill prey.

Unfortunately, since the mid-twentieth century, the proliferation of engines, propellers, sonar and explosions have turned the oceans into a noisy environment that hinders communication, orientation and feeding of cetaceans (Lopez et al, 2003).

The whales are now facing a series of environmental threats overwhelming product of human action. There are an increasing number of tests that show how hurt the whale, especially whales, climate change, the decrease in the ozone layer, chemical and noise pollution, bycatch, and the scarcity of prey product overfishing (Greenpeace, 2001).

Many cetacean species are listed by the International Union for Conservation of Nature (IUCN) as “vulnerable”, “endangered” and “endangered” (Romero et al, 1991). In the Red Book of Venezuelan Fauna 1999, reported 14 species of cetaceans, of which 10 are classified as “Insufficiently Known”, 2 “Lower Risk – near threatened” 2 type “Vulnerable” (Rodriguez and Rojas, 1999).

Noise pollution in the marine environment is produced in a range of frequencies and levels, the primary source includes ships, seismic, sonar, explosions and industrial activity (Gordon and Moscrop, 1996, National Research Council 2003). However, small boat traffic and large, produce low frequency sounds made by the most powerful man. A tone of 6.8 Hz of a giant oil can be detected at a distance between 139 and 463 km, with source levels of 190 dB (Gordon and Moscrop, 1996).

Despite the extraordinary acuity echolocation for cetaceans; and this time even that depends upon it almost completely, regularly include collective and individual strandings. There are the unknowns of how such intelligent animals, with domains shown widely navigation, suddenly lose their sense of direction and move towards sandbanks where they can not break free.

And even more puzzling then rescued and helped by people, they return to shore. There is an assumption of a form of auditory illusion susceptible to disorient the whales (Jacome, 1990). Of the 48 strandings recorded and reported in Venezuela between 1841 and 1992, it was determined that 56% were marked by diverse human intervention (Agudo, 1992).


* Determine the existence of effects of noise on cetaceans.

Describe the main types of marine noise pollution.


All odontocetes have large fat deposits on the forehead called the melon, in front of the skull and lower jaw just below an area where the bone is very thin and reaches the middle ear area. Such deposits are unique in the animal kingdom, and remarkable for a number of reasons.

First are quite large relative to the size of the animal, metabolic energy represents a huge potential, but apparently not used as storage tissues. Secondly, the chemical composition of this fat is markedly different from the current composition of the body fat and they eat a normal diet. Thirdly, the shape and position of these deposits is so important that there have been significant changes in form and structure of the skull to make room (Maldonado and Alcala, 1996).

Cetaceans emit two kinds of sounds, one high frequency calls used for echolocation clicks, and low frequency sounds such as whistles, squeaks and squawks gusts which serve the communication between them.

To explore their environment dolphins emit a click or a series of clicks whose frequency varies from 2,000 cycles to over 10,000 cycles per second. Being able to navigate, calculate distances, size, shape, structure and density of objects. The information provided by an echo are at least four orders: on the direction, frequency variations, the amplitude of the sound and the time that elapses from the time of issue until the return echo (Jacome, 1990; Maldonado and Alcala, 1996).

The air breathed in through the spiracles (breathing hole), which remains closed during the dive, is led through a complicated system of “poll”, consisting of several tabs vibrating and resonating chambers that produce ultrasound. These are reflected in the surface of the skull, which acts as a parabolic reflector, directing the sound into the melon. The melon acts as a sound lens, so that sounds very effectively addressed.

The returning echoes are collected in the lower jaw, where there is a gap filler throughout fat composition similar to the melon, and driven to the inner ear. Hence, in the form of nerve pulses are sent to the brain and analyzed. The amount of nerve tissue that connects the middle ear to the brain of odontocetes is more than twice that in humans (Maldonado and Alcala, 1996).

The toothed whales are the only ones who have bought a real capacity for echolocation, baleen whales use low frequency sounds to communicate and create “songs” complex, but they have some sense comparable to the sound of odontocetes has to be, at best cases, very primitive.

There are data on some species of baleen whales emit clicks often quite specific and has been proposed that could have the function of sonar to detect objects and determine the depth, but not proven (Maldonado and Alcala, 1996).

Experimental studies of the ability to listen have been conducted a few odontocetes (Gordon et al, 1998; National Research Council, 2003). It is assumed that baleen heard in the same frequency range of sounds they produce, about 5 to 10 Hz (Richardson et al, 1995).

Soviet researchers believe that a particular language of cetaceans is its ability to combine, with varying degrees of complexity, indivisible elements (something of phonemes or sounds of the alphabet of human speech) in complicated sequences of sounds similar to words and phrases. Scientists say there are certain regularities in the structure of these signals “phrases” of cetaceans, the hierarchical nature in the use of some elements of the alphabet, the block structure in the formation of complex signals, the existence at least three and at least five levels of group of identical signals, among other features.

Scientists believe that this type of training dolphins signal is typical of communication systems called open type (which include also human speech), which serve to convey complex information (Maldonado and Alcala, 1996).


The highest mortalities of cetaceans, except those caused by infectious agents, are produced by human activities, chemical pollution from industrial discharges or accidents, the leading maritime traffic noise pollution and pedestrian accidents, drift nets and other potentially dangerous objects , destruction of coastal and associated ecosystems, and tourist activities such as tourism, mass sightings without control or regulation (DELPHIS, 2004).

In the past five decades, acoustic research has focused substantial effort on the study of whales, so it now has enough scientific data on biological sonar system (bio-sonar) and dependence of the acoustic signals as a source information and communication system in the marine environment.

Underwater noise produced by human activities is increasing every day, including the shipping, exploration and production of oil and gas, industrial and military sonar, the sound sources of industrial testing, underwater explosives, etc. In fact, there is no corner of the world that is not affected by noise pollution.

Within the set of risk factors which affect the marine habitat, this pollution is one of the greatest threats to global short-term and for the balance of the oceans. Since the whales rely on sound in all aspects of their lives, no doubt, are particularly vulnerable to man-made noise sources (Lopez et al, 2003).

Cetaceans are highly dependent on their hearing aid for their survival. Many species use sound to locate prey, navigate and communicate, reaching considerable distances in the case of many species of large whales. The cetologists are increasingly concerned about ocean noise pollution from heavy traffic resulting from shipping, seismic surveys, oil extraction or sonar devices, elements that may be having significant negative impacts on many species (Lee et al, 2003).

Studies on the responses of cetaceans to noise pollution include avoiding the source of the noise and disruption of behavior (Gordon and Moscrop, 1996, Moore and Clarke, 2002, Williams et al, 2002). Some odontocetes sometimes approach boats and swim parallel to them, and accustomed to watching the marine traffic approaching ships, apparently to socialize (Lusseau, 2003; National Research Council, 2003). The effect of noise on the physiology and psychology of marine mammals is poorly understood (Richardson et al, 1995).

In light of recent mortalities in Spanish waters, it seems clear that noise sources at different levels of intensity, may adversely affect cetacean populations. The impact of these sources may vary significantly from inconvenience and displacement of populations to injuries of varying severity in the auditory system: slight, and possibly reversible, severe, causing permanent deafness and even immediate death of the animal (Lopez et al, 2003).

The modernization and increased maritime traffic, along with practices of geological exploration, oil exploration and the military use of active sonar in Spain become particularly sensitive to existing cetacean populations in waters such as the Canary Islands, where most recent data available , and probably the Strait of Gibraltar and the Balearic Islands.

However, one should not rule out the impact on other areas not so far examined (Lee et al, 2003).

Affect oil rigs in the distribution of whales (Balaena mysticetus) at distances of more than 50 km (Schick and Urban, 2000). But there are no experiments to demonstrate conclusively the relation of cause and effect, levels of 143 db in the range of 20 to 1000 Hz were determined at 1 km from an oil platform in California, indicating that a wide range of frequencies are audible at significant distances from these platforms. The drills used in the extraction of oil generate sounds with strong low-frequency tones (<20 Hz) (Gordon and Moscrop, 1996).

Current scientific knowledge about the effect of noise on marine mammals and their habitat is insufficient to understand the relationship between frequency, intensity and duration of exposure that can lead to negative consequences. Given these uncertainties are considered:

* It is urgent to investigate the effects of man-made noise on marine mammals under the highest standards of scientific credibility and public avoiding conflicts of interest.

* We must develop and implement mitigation measures noninvasively.

* The use of intense acoustic sources should be limited in areas of concentration of cetaceans to know its effects, short or long term, in marine mammals.

* The design of objective parameters to assess the conservation of marine biodiversity is needed to establish national and European regulations on marine noise pollution (Lopez et al, 2003).


One of the major threats to cetaceans is related to the exponential growth of maritime traffic in the last decades (Lopez et al, 2003). The low frequency noise produced by large ships and small boats high frequencies can have large effects on small cetaceans (Richardson et al, 1995, Gordon and Moscrop, 1996).

Until the advent of steam engines, the sea was an ideal medium for the use of sound by cetaceans, both to communicate, navigate and feed. But besides noise pollution, the boats are now experiencing a new threat to many species of cetaceans.

In 1985 the passenger ship that performed Princesa Teguise online las Palmas – Santa Cruz de Tenerife, collided with a whale killing it as well as a passenger. Despite this accident, since then the lines of high-speed ferries have proliferated in different locations throughout the country, coinciding in places with major areas of interest to food and migration of various species of cetaceans (Lopez et al, 2003) .

The study of Zacharias and Gregr (2004) found that the vulnerability of two groups of whales under four water stress, ferry traffic, commercial boat traffic, small boat traffic and potential oil production offshore; was relatively similar, however the near-shore species were more sensitive to coastal activities as oil production, traffic, ferries and small boats.

30 years ago created a new industry, whale watching, this is a seemingly innocuous search of whales for tourism. In the absence of industry codes of conduct that has brought new dangers to whales, while watching from the ground is harmless, the large number of ships moving very fast and noisy operation may interrupt behaviors such as feeding and reproduction in addition to causing physical damage (Stone et al, 2003).

Three of the most important areas for cetaceans in the Spanish coast, the Canary Islands, the coast of Galicia and the Alboran Sea, are key to international maritime traffic. Over 20% of the maritime traffic passes through these waters.

In addition to these merchant ships of note is the proliferation of boats engaged in whale watching tourism and other such personal watercraft or boat causing slight discomfort for the animals settled persecution. Currently exists only in the Canary Islands legislation that prevents the inappropriate approach of these vessels to cetaceans, which may not only cause a collision risk, but stress can get to endanger the animals (Lopez et al, 2003).


Seismic measurements are usually conducted using air guns that generate mainly low frequency sounds and short pulses in a split second and repeated every 5 to 10 seconds. Although normally have pointed down a significant amount of sound energy is projected from the sides.

Levels above 200 dB source have been measured (Gordon and Moscrop, 1996). Studies of marine mammal responses to earthquakes have been documented to conduct more than 10 km for blue whales (McDonald et al, 1995) and 8 km for humpback whales (McCauley et al, 1998). For this reason, many studies suggest a schedule for seismic surveys during periods when the potential affected species are absent (LGL Consulting 2000; Environmental Australia, 2001, Moore and Clark, 2002).


The recent coincidence in space and time in military exercises and mass strandings of cetaceans, especially in species of deep immersion has produced alarm about the impact that this technology can cause marine mammals. Although the current sonar systems are not the only or main cause of noise problems, if they are a clear example of what can be harmful anthropogenic noise in its most acute, lethal (Lee et al, 2003).

Active sonar is basically a submarine radar by emitting sounds allows the composition of an image and object detection by the reception of the echo produced by reflection. Due to the physical characteristics of sound that travels 4.5 times faster in water than air and low frequencies are propagated at a greater distance (Lopez et al, 2003; Guevara, 2004).

The Spanish navy sonar has great power and medium-range use any sunken object, especially submarines. These sonars have been implicated in mass strandings of beaked whales, little-known species and low rate of stranding. The most recent cases have occurred in the Bahamas in 2000 and in the Canary Islands in 2002, in which these systems were involved underwater sonic detection.

The extensive use of these systems by NATO ships in Spanish waters and Europe represents a clear risk factor for populations of cetaceans. Even more when they know the effect of a combination of sonar as a possible negative impact enhancer factor (Lopez et al, 2003).

Considering the direct or indirect lethal capacity of these active acoustic systems may not take into consideration the long-term damage they may suffer exposed populations. The risk of marine mammals that produce these sonar makes imperative to study and monitor these activities, establish safety limits and mitigation measures to establish its feasibility and if the parameters on which to develop (Lee et al, 2003).


The SURTASS LFA or LFA is the term that is known to a sonar system which stands for precision Surveillance Towed Array Sonar System (Sonar System Monitoring by Means of Lattice Sweep) Low Frequency Active Sonar (Low Active Sonar frequency). It is based on the use of sound waves of high intensity (greater than 200 dB) and low frequency (between 450 and 700 Hz) that can travel longer distances and detect underwater targets hundreds of miles away.

Tens of waves emitted during periods of a few seconds (about 250 in 4-5 seconds) that hit and bounce off the objects to a receiver that interprets sounds can also be used for a minute or more at intervals of 10 to 15 minutes . The issuer is suspended from the boat about 50 meters deep (Guevara, 2004).

The LFA has been recently implemented by the U.S. Navy, this system also make sounds of high intensity through 18 emitting elements, uses low frequencies to substantially increase its range. The potential impacts on large whales, who use similar frequencies, is of great concern to the addition of its intended use in all oceans (Lopez et al, 2003).

The aim of this system of sonar in military vessels is being able to precisely locate the submarines (both nuclear and diesel), including submarines quieter or even unemployed. NATO and especially the U.S. Navy aims to implement this system in their boats to cover 75% – 80% of the world’s oceans (Guevara, 2004).

The LFA may have effects on cetaceans up to 100 miles away. The resonance of the sonar causes vibration of all body cavities, trachea, jaws, sinuses, head and internal organs, with the greatest impact on those containing air. Can cause bleeding in the lungs and ears even destroy them (Guevara, 2004).

In 1997, the MMPA, the U.S. Congress Commission on Marine Mammals presented a report that acknowledged the impact of LFA sonar on cetaceans, indicating that this could produce effects such as death from bleeding in the lungs and other tissue trauma, partial or total hearing hindering communication, stress and other psychological disorders, making individuals more vulnerable to diseases such as viruses, bacteria and parasites, changes in migratory routes avoiding the usual areas of feeding and reproduction, and other behavioral disorders; If these effects are severe or continuous basis could cause reproductive failure and survival, declining populations and putting at risk the perpetuation of the species.

Between 1996 – 1998 U.S. Navy tested its LFA on whales in Hawaii, the evidence showed that modified whales disappearing migrations and movements in the area and in the case of humpbacks, stopped their singing. In these experiments with 140 decibels was sufficient to cause the whales leave the area, although some researchers believe that more than 120 dB and is sufficient to be detrimental to the health of these animals.

According to own studies of the Navy’s LFA sonar sound waves can generate 140 dB able to exceed 300 miles (Guevara, 2004).

An environmental impact study conducted by the U.S. Navy, generated by reports of numerous social groups that showed their concerns about the military exercises showed that beaked whales could be affected by these operations. In 2001, a year after the death of the Bahamas, U.S. Navy officials announced that, based on autopsies and other evidence of stranded animals, it was “highly probable” that were caused by sonar transmissions of the Navy (Guevara, 2004).


* Cetaceans have a number of conditions and human activities that seriously affect the preservation of their species, the whale fishery and chemical pollution in the waters have been clearly studied, but do not really know the extent of involvement of marine noise pollution, which has grown exponentially in recent years.

* You must regulate marine traffic and the activities of watching, when the vessels operating in areas frequented by whales.

* It should study and classify the main focus areas where cetaceans to announcements on marine protected areas in order to control human activities.

* The oil extraction process produces alterations in cetaceans, the study of these effects can be obtained new equipment and recommendations for minimizing the stress.

* Sonars generally affect communication systems and location of the whales, but has been determined that new and powerful low-frequency sonar and long-range cause mass deaths of cetaceans, making study and regulation imminent as this may affect in addition to other marine organisms, and even endanger the lives of divers.


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Cesar A. Mac-Quhae R.

La Salle Foundation of Natural Sciences

Hydrobiological Research Station of Guyana

Puerto Ordaz – Venezuela