Science

  • Issue 121 / January - February 2018



    Who Taught Science to Dolphins?

    Yakup Kagan

    Teaching science is sometimes a challenge, and teachers need to find ways to draw kids’ attention. Young children are naturally interested in the behavior of animals. They especially enjoy making friends with pets and observing birds. Teaching science to kid with examples from animals always work. And dolphins are always a great example to show that science is out there in the nature, and even animals can make use of it in the best possible way.



    Dolphins produce clicking sounds to navigate, to collect information about their environment, and to locate food. Each and every dolphin has a different sound just like every human being. Distinguishing between different sounds, they have been known to instruct each other, receive instructions, and act accordingly.



    Sounds for hunting and navigating

    Dolphins send out clicking sounds. When those sounds hit an object, they bounce back vibrations to the dolphins. These echoes allow them to identify where objects are located. It also gives them information about the location of the object and some indication of the shape and size of it. This system is called “Echolocation” or “Sonar,” just like what a submarine uses to navigate while underwater.



    How can dolphins analyze the information contained in these echoes?



    Dolphins produce sounds with their larynx and a complex system of cavities connected to their blowhole. The sounds used in echolocation are a rapid series of clicks. The clicks contain a wide range of frequencies, but most of the sound energy is in the range between 50,000 to 200,000 cycles a second, or hertz. These high frequencies are necessary for echolocation in water. Because sound waves travel at about 340 meters a second (m/s) in air, and the speed of sound in water is five times greater than in air. The wavelength of a sound of a given frequency in water is five times longer than in air. Dolphins must generate frequency five times higher to achieve the same resolution.



    How do dolphins use sound to gauge the distance and speed of objects around them?

    The physical phenomenon of sound is defined to be a disturbance of matter that is transmitted from its source outward. Sound is a type of energy made by vibrations. Sound energy cannot be produced on its own. Sound waves move like ripples of water after a pebble has been dropped on the smooth surface of a pond. When any object vibrates, it causes movement in the air particles. This movement, called sound waves, work travel through a medium by passing vibrations from molecule to molecule until the particles run out of energy. 



    Sound waves need to travel through a medium such as a solid, liquid, or gas. The molecules in gases are not packed as tightly as liquid. Therefore, the spacing of the molecules enables sound to travel much faster through a solid than a gas. Energy goes into compressing and expanding the surrounding water, occurring slightly higher and lower local pressures. These cause compressions (high pressure regions) and rarefactions (low pressure regions).




    A sound wave travels approximately at 1,500 m/s in water. Another phenomenon related to the perception of time delays between two events is an echo. A person can often perceive a time delay between the production of a sound and the arrival of a reflection of that sound off a distant barrier. The time delay between the holler and the echo corresponds to the time for the holler to travel the round-trip distance to the canyon wall and back. A measurement of this time would allow a person to estimate the one-way distance to the prey. For instance, if a dolphin hears an echo in 0.2 seconds after making the holler, then the distance to the prey can be calculated as follows: distance = v x t = 1,500 m/s x 0.1 s = 150 m.



    How can any dolphin analyze the information contained in these echoes?

    There is still plenty that isn’t known about dolphin echolocation. There are two hypotheses about how dolphins produce sound underwater. Scientists are not sure which hypothesis is correct. According to the accepted views, dolphins have a fat-filled organ in the front part of the head described as a melon. The melon acts like a lens for sound waves, focusing the sound waves into a narrow beam. Dolphins generate a wide variety of clicks. The clicks they use for echolocation are of a higher frequency than those used for other forms of communication. This improves resolution and allows smaller prey to be located. The clicks are generated in a series of interconnected passages behind the melon. When the sound strikes an object such as a prey fish, some of the sound is reflected back toward the dolphin. Another fat-filled cavity in the dolphin's lower jaw acts as a receptor for this sound. The sound is carried from the fat-filled cavity to the middle ear and perceived by the animal's brain. Consequently, as soon as an echo from one click is received, the dolphin generates another click. The time lapse between click and echo enables the dolphin to determine the distance between it and the object. The difference in sound intensity received by each ear allows the animal to determine the direction. By emitting a series of clicks and listening to the echoes, the dolphin is able to locate and follow its prey. Yet the dolphin’s sonar is highly advanced and can pinpoint exact information about its surroundings ranging from size, distance and even the nature of the object.



    After all these findings, one cannot help but ask, “Who taught science to dolphins?”



    References



    1. Richmond, Elliot. "Echolocation." Animal Sciences. 2002. Encyclopedia.com. 9 Sep. 2015<http://www.encyclopedia.com>.

    2. http://www.jiscdigitalmedia.ac.uk/guide/the-physical-principles-of-sound

    3. Beggs, J., & Thede, D. (2001). Chapter 2. The Science of Sound and Digital Audio in “Designing web audio” book. " O'Reilly Media, Inc.".

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