Are Whales Beaching Themselves Stressed By Sonar?

Krysta Levac
Readability
6.6

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Read about why sonar could be causing some whales to beach themselves.

Imagine if accidentally hearing a private conversation could threaten your survival. This is what scientists suspect is happening to beaked whales when they strand themselves on land after hearing the underwater sounds of military sonar.

Beaked whales are fantastic divers. Cuvier’s beaked whales can dive almost three kilometres in search of squid to eat. (Nature, 2020) That’s about five-and-a-half CN Towers! (CN Tower, n.d.) Military sonar can interrupt a whale's dive for food. If this occurs they will sometimes wash ashore with signs of decompression sickness. Human divers suffer from decompression sickness when they surface too quickly. What is the connection between beaked whale strandings and military sonar? And why would beaked whales suffer from decompression sickness if they are such excellent divers? Let’s look into this to understand better.

Sound underwater - a different kind of wave

Sound moves as a wave underwater, but not like waves that crash onto the beach. A vibrating sound source starts a wave of compression and expansion of water molecules. It’s similar to how sound moves through air. Sound waves travel very well underwater. In fact, the speed of sound is almost five times faster in seawater versus air. (DOSITS(a), n.d.) Changes in ocean temperature, depth and salinity change how fast and how far sound travels underwater. (DOSITS(a), n.d.) (NOAA National Ocean Service, 2021)

Sonar operator in the sonar room of a U.S. Navy vessel.
Sonar operator in the sonar room of a U.S. Navy vessel. (Source: U.S. Navy, Flickr)

What is Sonar?

Sonar is an acronym for sound navigation and ranging. It is a tool to “see” underwater using sound waves. There are two main types of sonar: passive and active.

Passive sonar devices are just receivers that listen for underwater sounds. They are used to find whales and dolphins that make noises to communicate. The military also uses passive sonar to listen for submarines.

Active sonar devices have a sound source, called a projector, in addition to a receiver. The projector sends sound waves into the water. The sound waves reflect off underwater objects and return to the receiver. Active sonar measures precisely how long it takes the sound to return to the receiver. It also measures changes to the sound quality. These measurements can identify objects such as the ocean floor, shipwrecks, fish and whales. Active sonar also determines how far away the objects are. (DOSITS(b), n.d.)

There are many different types of active sonars. A Mid-frequency active sonar (MFAS) uses sound waves with a frequency between 1 kHz and 10 kHz. (kHz is the abbreviation for kiloHertz and one kHz is 1000 wave cycles per second.) Naval forces around the world use MFAS for submarine detection and training exercises. (D'Amico & Pittenger, 2009)

How is MFAS connected to beaked whale strandings?

Beaked whales can hear the frequencies used for MFAS. (Picher-Labrie, 2019) They also spend a lot of time diving to the same ocean depths used for MFAS. (Picher-Labrie, 2019) In the mid-1980s, scientists studied mass stranding events (MSEs) of Cuvier’s beaked whales. They found that MSEs happened at the same time as naval training exercises around the Canary Islands in Spain. (Bernaldo de Quirós et al., 2019) This association was later confirmed in Greece and the Bahamas. (Bernaldo de Quirós et al., 2019) MSEs are when two or more animals wash ashore at approximately the same place and time. Naval MFAS is also associated with strandings of individual beaked whales. (Simonis et al., 2020) (NOAA Fisheries, 2020)

Cuvier's Beaked Whale stranded on the shore in Newfoundland
Cuvier's Beaked Whale stranded on the shore in Newfoundland (Source: Silver Leapers, Flickr)

Why are beaked whales stranding?

Sometimes, stranded whales survive if humans quickly roll them back into the ocean. When they don’t survive, scientists can dissect them to try to figure out what caused their stranding and death. The beaked whales that died after MFAS exposure had gas bubbles where they did not belong, in their veins and organs. This looked exactly like decompression sickness in humans. (Bernaldo de Quirós et al., 2019) (Picher-Labrie, 2019)

What is decompression sickness? During a deep dive, the weight of water causes a lot of pressure on the body. This pressure forces extra breathed gas (mostly nitrogen) to dissolve in blood. Human divers must surface slowly to give their bodies time to exhale the extra gas. Surfacing too quickly traps gas bubbles in blood and tissues. Decompression sickness is also called the “bends” because people bend over from the pain.

Why would beaked whales get the bends?

Decompression sickness, also called the bends, is caused when a diving animal or human surfaces too quickly. When underwater, pressure is much higher than at the surface. As a human or animal surfaces, those gases under a smaller pressure want to take up more space. If surfacing slowly, the gas diluted in blood and tissues are evacuated safely. But if those gases are not given enough time to be liberated in those safe ways, they can go into places they can cause problems, such as the articulations, lungs and in some deadly cases, the nervous system and brain.

Decompression sickness in beaked whales was a surprising discovery. Marine animals that dive have adaptations to avoid this life-threatening condition. They adapt their behaviour to swim to the surface slowly, just like human divers. They also adapt some of their body functions (physiology) such as heart rate, blood flow, and gas exchange in the lungs. (Bernaldo de Quirós et al., 2019) These adaptations seem to fail in some beaked whales that are exposed to MFAS. Scientists think that MFAS can cause a lot of stress to beaked whales. This stress changes both their diving behaviour and diving physiology. Sonar-stressed whales don’t decompress normally and can strand themselves.

This story is complicated. Sometimes, beaked whales are exposed to MFAS and appear to be just fine. And sometimes, beaked whales strand themselves with no MFAS exposure. Different populations of whales - and even different individual whales in one population - can react differently to MFAS. (Bernaldo de Quirós et al., 2019) Marine mammal scientists are working to solve this mystery.

What is being done to protect beaked whales?

To protect beaked whales and other marine mammals, the Canary Islands banned MFAS in 2004. Not a single MSE has been observed in the area since. (Bernaldo de Quirós et al., 2019) In 2015, the U.S. Navy agreed to limit MFAS use in parts of the Pacific Ocean that are important habitats for marine mammals. (Morell, 2015) However, the U.S. Navy was allowed to relax some of these restrictions in 2020. (Duhamel, 2020) 

Marine mammals may be accidental victims of military training. In the wrong place at the wrong time, hearing the wrong conversation.

 

Starting Points

Connecting and Relating

  • Would you be willing to pay a special tax to fund whale research and conservation? Why/why not?
  • Have you ever been whale watching? Have you ever listened to whale vocalizations, such as those of the humpback whales? How did this make you feel?

Connecting and Relating

  • Would you be willing to pay a special tax to fund whale research and conservation? Why/why not?
  • Have you ever been whale watching? Have you ever listened to whale vocalizations, such as those of the humpback whales? How did this make you feel?

Relating Science and Technology to Society and the Environment

  • Whale populations have been affected by humans in many ways and many species have been listed as endangered. Can you name some of these risks?
  • What are some of the things being done to help whales survive? Can you find an example where conservation efforts have managed to take species off the endangered list?
  • According to the Department of National Defence, a role of the Canadian Army is to become environmental stewards. Do you think this is a good idea? How can the army help protect wildlife?

Relating Science and Technology to Society and the Environment

  • Whale populations have been affected by humans in many ways and many species have been listed as endangered. Can you name some of these risks?
  • What are some of the things being done to help whales survive? Can you find an example where conservation efforts have managed to take species off the endangered list?
  • According to the Department of National Defence, a role of the Canadian Army is to become environmental stewards. Do you think this is a good idea? How can the army help protect wildlife?

Exploring Concepts

  • How do whales and dolphins communicate?
  • Have you ever seen a sonar on a boat? What could it detect?
  • Compare the frequencies of whale communications with that of human hearing. What did you notice?
  • In what situations can humans suffer from decompression sickness?

Exploring Concepts

  • How do whales and dolphins communicate?
  • Have you ever seen a sonar on a boat? What could it detect?
  • Compare the frequencies of whale communications with that of human hearing. What did you notice?
  • In what situations can humans suffer from decompression sickness?

Nature of Science/Nature of Technology

  • Do you think humans should do more to study the possible impacts of using a new technology in natural habitats? Explain your reasoning.
  • Why is it so complex to identify the cause of marine mammal beachings? How could we better understand the relation between the beachings and sonar use?
  • Design an experiment that would study the possible impacts of technology such as sonar on marine species.
  • New technologies have allowed scientists to much better understand our oceans. However, sometimes the study itself can have adverse effects on the animals studied. Do you think the discomfort to animals is worth the scientific knowledge we can gain to be able to better understand and protect the species? Explain.

Nature of Science/Nature of Technology

  • Do you think humans should do more to study the possible impacts of using a new technology in natural habitats? Explain your reasoning.
  • Why is it so complex to identify the cause of marine mammal beachings? How could we better understand the relation between the beachings and sonar use?
  • Design an experiment that would study the possible impacts of technology such as sonar on marine species.
  • New technologies have allowed scientists to much better understand our oceans. However, sometimes the study itself can have adverse effects on the animals studied. Do you think the discomfort to animals is worth the scientific knowledge we can gain to be able to better understand and protect the species? Explain.

Media Literacy

  • Have you read or heard about whale beachings in the news? Where was it? What reasons did the journalists state as the possible cause? Was it backed by scientific evidence? Was a subject matter expert interviewed?

Media Literacy

  • Have you read or heard about whale beachings in the news? Where was it? What reasons did the journalists state as the possible cause? Was it backed by scientific evidence? Was a subject matter expert interviewed?

Teaching Suggestions:

  • This article supports teaching and learning of Physics, Biology and Ecology related to Frequencies, Sound, Human Impacts on Wildlife, Animal Physiology, Animal Communication and Oceanography. Concepts introduced include sonar, pressure, effect of pressure on physiology, mapping of the oceans, speed of sound in water, Hertz, gas exchange in circulatory system.
  • After reading the article, teachers could have students complete a Concept Definition Web learning strategy to explore the concept of mole (mol). Ready-to-use reproducibles for this article are available in [Google doc] and [PDF] formats.
  • After reading this article, students could summarize and consolidate their understanding of the article content using a Issues & Stakeholders learning strategy. Ready-to-use Issues & Stakeholders reproducibles for this article are available in [Google doc] and [PDF] formats.

Teaching Suggestions:

  • This article supports teaching and learning of Physics, Biology and Ecology related to Frequencies, Sound, Human Impacts on Wildlife, Animal Physiology, Animal Communication and Oceanography. Concepts introduced include sonar, pressure, effect of pressure on physiology, mapping of the oceans, speed of sound in water, Hertz, gas exchange in circulatory system.
  • After reading the article, teachers could have students complete a Concept Definition Web learning strategy to explore the concept of mole (mol). Ready-to-use reproducibles for this article are available in [Google doc] and [PDF] formats.
  • After reading this article, students could summarize and consolidate their understanding of the article content using a Issues & Stakeholders learning strategy. Ready-to-use Issues & Stakeholders reproducibles for this article are available in [Google doc] and [PDF] formats.

Learn more

What is Sound and How do we Hear it?
Learn the basics about sound in this Let’s Talk Science article. What is it? How do we hear sounds? How is sound measured?

Career Profile: Andrea Ruohoniemi
This Let’s Talk Science Career Profile gives you a glimpse of what it’s like to work as a Weapons Engineering Sonar Technician in the Royal Canadian Navy.

Cuvier’s Beaked Whale Research: Operation Divina Guadalupe
Learn more about Cuvier’s beaked whales in this article from the Sea Shepherd Conservation Society. The embedded video shows footage of these elusive animals.

Scientists “See” Ocean Floor via Sonar
This National Geographic video explains how sonar is used to map the ocean floor.

Why Don’t Marine Animals Get “The Bends”?
This SciShow video explains how marine animals have adapted to diving and how they can avoid decompression sickness.

References

Bernaldo de Quirós, Y., Fernandez, A., Baird, R.W., Brownell, R.L., Aguilar de Soto, N., Allen, D., Arbelo, M., Arregui, M., Costidis, A., Fahlman, A., Frantzis, A., Gulland, F.M.D., Iñíguez, M., Johnson, M., Komnenou, A., Koopman, H., Pabst, D.A., Roe, W.D., Sierra, E., … Schorr, G. (2019, January 30). Advances in research on the impacts of anti-submarine sonar on beaked whales. Proceedings of the Royal Society B286(1895). http://doi.org/10.1098/rspb.2018.2533

CN Tower. (n.d.). CN Tower: History: Astounding. 

D'Amico, A., & Pittenger, R. (2009). A Brief History of Active Sonar. Aquatic Mammals35(4), 426-434. 10.1578/AM.35.4.2009.426

DOSITS(a). (n.d.). How fast does sound travel? Discovery of Sound in the Sea. 

DOSITS(b). (n.d.). Sonar Technology. Discovery of Sound in the Sea. 

Morell, V. (2015, September 16). U.S. Navy to limit sonar testing to protect whales. Science News. 

Nature. (2020, September 23). A Smiling Whale Makes a Record Deep Dive

NOAA Fisheries. (2020, February 19). Beaked Whale Strandings in the Mariana Archipelago May Be Associated with Sonar. NOAA Fisheries. 

NOAA National Ocean Service. (2021, February 26). How far does sound travel in the ocean? 

Picher-Labrie, J. (2019, February 15). Correlation confirmed between military sonar and beaked whale mass strandings. Whales Online. 

Simonis, A., Brownell, R., Thayre, B., Trickey, J., Oleson, E., Huntington, R., & Baumann-Pickering, S. (2020, February 26). Co-occurrence of beaked whale strandings and naval sonar in the Mariana Islands, Western Pacific. Proceedings of the Royal Society B287(1921). https://doi.org/10.1098/rspb.2020.0070