Dolphin Beachings Linked to Sonar
A record number of dolphins have beached themselves at Cape Cod in Massachusetts and in Peru this year. During January and February, over 175 dolphins beached themselves in Cape Cod, Mass., and over two hundred dolphin beachings were discovered on the beaches of Peru.
Marine researchers have been investigating the possible causes. While some consider natural environmental issues like enclosed bays, or tough currents, the record numbers this year indicates other causes. Scientists have ranged in their hypotheses.
The warming ocean waters is one cause researchers have taken seriously. Ocean temperatures have risen over one degree Farenheit in the past decade, and even warmer currents have been found in a number of ocean habitats.
Pollution in the water is also high on the list, as the amount of degrading plastics, nitrogen runoff from chemical fertilizers, oil spills and other pollutants have been alarmingly increasing in the oceans worldwide. Many of these pollutants accumulate up the food chain, poisoning the larger sea mammals like dolphins gradually
The increasing use of sonar by military submarines and warships, especially during naval exercises, by far has gained the most credibility, and recent research confirms this thesis. Because both dolphins and whales have extensive sonar capability, and their sensitivity to sonar is so strong, research has connected their beachings to U.S. Naval exercises. This led to a 2008 Supreme Court battle between environmental groups and the U.S. Navy. The Court ruled that the Navy had to begin developing other tools that would not harm whales and other marine life.
Researchers from Massachusetts’ Woods Hole Oceanographic Institution, Texas A&M University-Corpus Christi, the Marine Mammal Rescue and Research facility, the International Fund for Animal Welfare, and the Chicago Zoological Society have recently conducted a study of 22 self-stranded (beached) dolphins. They found that the kidneys of 21 of the 22 stranded dolphins contained gas bubbles. The bubble content was identical to the gas bubbles found among the tissues of whales and dolphins that have been found stranded during naval exercises.
The connection between the tissue bubbles and the beachings appears to be related to their need to decompress as they surface and dive. Should their decompression system not be working properly, they need to find an avenue for decompression. Beaching themselves appears to be an attempt to achieve such a decompression.
The researchers also tested wild dolphins not stranded, and found no such bubbles in their tissues. They also found that following a beaching, dolphins appear to tolerate the bubbles and some improve after returning to the sea. At least until faced with the next military naval exercise.
In 2011, an international team of marine scientists supported by the U.S. Office of Naval Research conducted a whale behavior study published in the scientific journal PLoS ONE. The study showed that mid-frequency sonar waves in the range of 140-160 dB significantly altered whale activity. This mid-range frequency, also used by naval warships, helicopters and submarines, caused whales to react negatively. The researchers concluded that the whales are sensitive to these sonar devices.
Dolphins and whales use similar sonar sensory organs. Dolphins use sonar to communicate, navigate their positions, and understand the positions of their prey and other dolphins.
We might compare being in the ocean surrounded by sustained military sonar to being in close proximity to loud public sirens, such as those used for tsunamis and airplane bombing warnings. The intensity of these sirens after only a few minutes would drive any person as far away from the siren sound as possible.
In humans, our tympanic membranes and middles ears are also connected to our sense of balance and our body’s atmospheric pressure compression. This is why are ears pop when we climb to high altitudes or dive into deep water. Whale and dolphin sonar senses are also connected to their decompression facilities.
Another 2011 study from The Netherlands found that porpoises were sensitive to the helicopter long range active sonar (HELRAS) system. They found that the mammals were sensitive to amplitudes of 76 dB of HELRAS sonar arrays.
Previous studies have confirmed that whale beachings increased in regions and during times when there was an increase in Naval exercises.
The beachings of dolphins in Chiclayo, Peru occurred side by side with anchovy beachings. Researchers at the Peruvian Sea Institute are now assuming that whatever beached the anchovies also forced the dolphin beachings, indicating some kind of environmental pollutant. The connection with the anchovies has yet to be determined, but sonar has not been eliminated.
Whether it is chemical pollutants or sonar pollutants, humanity is increasingly interfering with the lives of those creatures that live around us. What is the real cause? The cause is humanity’s lack of respect for nature and the intelligence of our environment. Humanity’s assumption that we can conquer and control nature without responsibility, boundary or sensitivity is what is destroying the very environment we need to survive, and those beautiful creatures that share our environment.
By Case Adams, PhD. See the author’s books.
Dennison S, Moore MJ, Fahlman A, Moore K, Sharp S, Harry CT, Hoppe J, Niemeyer M, Lentell B, Wells RS. Bubbles in live-stranded dolphins. Proc Biol Sci. 2012 Apr 7;279(1732):1396-1404
Supin AY, Nachtigall PE, Breese M. Interaction of emitted sonar pulses and simulated echoes in a false killer whale: an evoked-potential study. J Acoust Soc Am. 2011 Sep;130(3):1711-20.
Kastelein RA, Hoek L, de Jong CA. Hearing thresholds of a harbor porpoise (Phocoena phocoena) for helicopter dipping sonar signals (1.43-1.33 kHz) (L). J Acoust Soc Am. 2011 Aug;130(2):679-82.
Dolman SJ, Parsons EC, Wright AJ. Cetaceans and military sonar: a need for better management. Mar Pollut Bull. 2011;63(1-4):1-4.
Zirbel K, Balint P, Parsons EC. Navy sonar, cetaceans and the US Supreme Court: a review of cetacean mitigation and litigation in the US. Mar Pollut Bull. 2011;63(1-4):40-8.
Kastelein RA, Steen N, de Jong C, Wensveen PJ, Verboom WC. Effect of broadband-noise masking on the behavioral response of a harbor porpoise (Phocoena phocoena) to 1-s duration 6-7 kHz sonar up-sweeps. J Acoust Soc Am. 2011 Apr;129(4):2307-15.
Tyack PL, Zimmer WM, Moretti D, Southall BL, Claridge DE, Durban JW, Clark CW, D’Amico A, DiMarzio N, Jarvis S, McCarthy E, Morrissey R, Ward J, Boyd IL. Beaked whales respond to simulated and actual navy sonar. PLoS One. 2011 Mar 14;6(3):e17009.