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Information Processing: Whale Communication

Clarification Statement: Emphasis is on systems of information transfer.

 

Assessment Boundary: Assessment does not include the mechanisms by which the brain stores and recalls information or the mechanisms of how sensory receptors function.

The above activity builds on the content below.

The above teacher presentation is useful to show students before begining the activity Harmonizing with Humpbacks, as it explores the basics of whale communication. There are presenter notes in yellow boxes in the upper, left corner.

Information Processing

<p>Fig. 1. Animals, such as humans, are exposed to various stimuli and that information is processed in the brain.</p>An organism’s ability to sense and respond to its environment enhances its chance of surviving and reproducing. Animals have external and internal sensory receptors that detect different kinds of information, and they use internal mechanisms for processing and storing it (Fig. 1). Each receptor can respond to different inputs (electromagnetic, mechanical, chemical), some receptors respond by transmitting impulses that travel along nerve cells. In complex organisms, most such inputs travel to the brain, which is divided into several distinct regions and circuits that serve primary roles. For example, some functions include visual and auditory perception, interpretation of information, guidance of motor movement, and decision making. In addition, some of the brain’s circuits give rise to emotions and store memories. Different organisms exhibit an array of sensory functions that can vary in complexity. For example, marine mammals such as cetaceans may process sounds differently than a marine invertebrate, like a sea urchin. Whales use sounds as a means of communication.


Whale Communication

<p>Fig. 2.&nbsp;Anatomy of sound production in humans.</p>The most effective means of communication in water is sound. Sound travels over long distances and is 4.5 times faster in water than in air. Many marine mammals have adaptations for producing and receiving sounds underwater. Sounds are generated when pressure waves travel through air or water. In humans, sound is generated when air is expelled from the lungs and moved through the larynx. The vocal cords in the larynx, along with the throat, tongue, lips, and teeth, change the sound into different vocalizations (Fig 2). The mechanism of sound production in cetaceans is complex and still being studied. Unlike with humans and other marine mammals, cetaceans do not need to exhale air in order to produce sound. Odontocete whales use echolocation, generating clicks, whistles, and pulses in the nasal system. Mysticete whales produce very low frequency sounds similar to groans, thumps, moans, and pulses.

<p>Fig. 3.&nbsp;Anatomy of underwater sound production in an odontocete whale</p>Cetaceans do not have an external ear structure to receive sounds and no opening to the ear canal. Scientists have evidence that sound vibrations pass through the skin and then are focused through the bones and fats in the skull to the inner ear (Fig. 3).

How Whales Sing

<p>Fig. 4. Humpback whales use sound to communicate for a variety of reasons. A male is pictured here in the singing position (head down, tail up).</p>

Humpback whales are famous for their complex song (Fig. 4). Only males sing, usually during mating season but singing can be heard in breeding grounds and in feeding grounds. The singer is usually alone in a head-down, tailup position. If the singer is following a cow and calf pair, he is called an escort. When another whale joins in on the song, he is called a joiner. Humpback whales do not have vocal cords. They produce sounds by pushing air through tubes and chambers in their respiratory system. Whale researchers study patterns on spectrograms to learn about why whales sing, and how they react to other whales around them. Hypotheses exist as to why whales sing, but researchers do not know the absolute reason. It is thought that males sing as a way to communicate their location to other males, attract females, navigate, find food, and communicate with each other.


Studying Whale Communication

<p>Fig. 5. A boat launches the laying of the cable from hydrophone to the shore station for radio acoustic ranging operations.</p>The U.S. Navy was the first to record whale songs in the 1950s by using underwater listening devices called hydrophones (Fig. 5). These are still the main instruments used to listen to, and record, whale songs today (Fig. 6). Computer programs have been developed to help deconstruct the complex vocalizations made by male humpback whales. These bioacoustic software programs create spectrograms that allow researchers to visualize the composition and patterns of individual songs (Fig. 7). Researchers record an individual’s song, and keep track of that individual over many years in order to better understand the reasons behind the vocalizations. For more detail on the evolution of studying sound, check out NOAAs Historical Timeline.

<p>Fig. 6. Modern hydrophones can be adapted to be used on Kayaks, such as this one pictured here.</p> <p>Fig. 7. Sound spectrogram illustrating the range of frequencies in a humpback whale song.</p>


Structure of Whale Songs

Scientists have been analyzing songs since the 1970s, and have discovered that patterns exist. For example, the basic structure of a whale song consists of a series of sounds or units, repeated in patterns over time called phrases. Each phrase is then repeated several times to comprise a theme. A complete song lasts from 8–15 minutes, and has a total of about 5–7 themes that are repeated during the song. The song can also be repeated and may go on for several hours. Over the years, the song of individuals slightly changes, but it is interesting to note that interacting populations of humpbacks share essentially the same song. Different populations have completely different songs; for example, the North Pacific population has a completely different song than the South Pacific population.


Noise Pollution

Scientists also study whale songs to learn about how noise pollution, caused by people, affects the behavior of whales. Human-produced underwater noise pollution is thought to disrupt any, or all of these vital functions. The physical effects of intense noise pollution can include hemorrhaging of the brain, lungs, inner ear, and eyes causing severe impairment in acoustic communication and other essential behaviors. Our knowledge of the biology of marine mammals is still growing although very little is known about the hearing capabilities of cetaceans. Current research at the Marine Mammal Research Program at the Hawai‘i Institute of Marine Biology is attempting to characterize the hearing frequency ranges of these animals to better understand how anthropogenic underwater noise pollution might affect them.  Ship engines, military sonar, and explosions used by oil and construction companies cause loud sounds under water that may cause changes in the whales’ behavior (Fig. 8). 

<p>Fig. 8. Human produced, or anthropogenic, noise pollution can be harmful to a nearby whale and interrupt it's own ability to communicate.</p><br />

Below is a list of sources of anthropogenic underwater noise pollution that are thought to be detrimental to marine mammals causing any, or all the physical damage previously described.

Types of Sound Pollution Description
Low Frequency Active Sonar (LFAS) This type of high-intensity sonar was designed by the military to track and detect submarines and other covert machines that operate underwater. The intensity of this sonar is in the 180–240 decibel range. This is equivalent in air to being 7 meters (20 feet) away from a rocket at takeoff. A large percentage of marine mammal carcasses being collected from beach strandings show signs of hearing damage, showing evidence that many mammals that strand may be doing so in response to hearing damage. Many recorded mass strandings have occurred during naval testing of LFAS.
Air guns Used for underwater exploration and monitoring of oil reserves as well as geophysical research, and often operate for long periods of time, producing frequent bursts. Sperm whales and blue whales that were located as far away as 370 kilometers (230 miles) from the air gun reportedly stopped vocalizing for up to 36 hours in response to the noise. Strandings have also been documented in close vicinity to these machines.
Shipping Cargo ships produce constant low frequency noises from their propellers that fall within the same frequency range that many whales use to communicate over long distances. The effects of shipping noise are hard to quantify because shipping vessels are very frequent in the world’s oceans. Some scientists, however, are concerned that interference from shipping noise could have large scale population level effects in the ability of individuals to communicate with each other over long distances.

For more info on noise pollution, check out NOAA's Soundcheck on Ocean Noise

 

Whale Communication Vocabulary

  • Anthropogenic: originating in human activity (typically environmental pollution).
  • Baleen: the internal feeding structure of baleen whales composed of a protein similar to human fingernails that hangs from the upper jaws of the whale’s mouth; functions to sieve through water and trap small food particles
  • Bioacoustics: the study of how animals use sound for communication and echolocation
  • Cetacean: member of the family of large aquatic mammals such as whales, dolphins, and porpoises. They have tails rather than hind limbs, and they have flippers instead of forearms.
  • Communication: the exchange of messages or information through speech, signals, writing, or behavior
  • Cow: the female of certain large animals, for example elephant, rhinoceros, whale, or seal.
  • Echolocation: the ability of animals to examine their surroundings using sound waves they produce that bounce off objects and are received back and interpreted
  • Hydrophone: an underwater microphone used to listen to, and record, whale song sounds
  • Joiner: a lone male humpback whale engaged in a singing behavior in response to another singer
  • Mysticetes: Baleen whales, large whales that feed using a filtering mechanism made up of baleen plates - Ex. humpback whales.
  • Odontocetes: Toothed whales that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species of toothed whales are described.
  • Singer: a lone male humpback whale engaged in a singing behavior
  • Spectrogram: A visual representation of the spectrum of frequencies of a signal as it varies with time. When applied to an audio signal, spectrograms are sometimes called sonographs, voiceprints, or voicegrams.
  • Underwater noise pollution: human-caused noise created by ship and recreational boat engines, props and sonar, oil drilling, near-shore construction, and military defense sonar
  • Whale song phrase: a series of sounds (units) repeated over time in patterns
  • Whale song theme: a repeated set of whale song phrases
  • Whale song unit: single, uninterrupted emissions of sound that last up to a few seconds
 
Representative Image: 
Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.