Tag Archives: Echolocation

What Makes a Dolphin a Dolphin?

Most everyone on the planet knows what a dolphin is and what they look like. Dolphins are incredibly popular animals and just happen to be one of the most charismatic of all marine mammal species. But you may not have known that dolphins belong to an order of species that encompasses many of our favorite mammalian relatives. This is the order Cetacea that contains both baleen whales as well as toothed whales, which is the one our familiar dolphins are a part of. Today we are going to talk about some differences between baleen whales and toothed whales and how we can identify what makes a dolphin a dolphin.

First off lets talk about baleen whales and toothed whales. The baleen whales scientific sub-order is officially called Mysticeti and contains whales such as blue whales, gray whales, and humpback whales. The toothed whales scientific sub-order is officially termed Odontoceti and contains whales like porpoises, orca whales, and of course dolphins! There are many similarities between the two sub-orders such as they both give live birth, have blowholes, and use sounds to communicate with each other, as well as many others. However, there are some glaring differences between the two that allow us to really define what a dolphin exactly is.

The first major difference is that Mysticetes use baleen, (large overlapping plates used to filter feed), to eat small organisms like krill. Odontocetes swallow their prey whole and use their teeth for grabbing and gripping instead of chewing. Secondly, Mysticetes are also mostly solitary animals only coming together for mating or when food is plentiful in a given spot whereas most Odontocetes, especially dolphins shown above, travel in pods. Thirdly, Odontocete jaws are much more asymmetrical (different on either side of the jaw) than Mysticetes so that they can receive sound waves from echolocation much better while they are feeding and locate their prey. Fourthly, sounds made by these two are different; Mysticetes produce much lower frequency songs to navigate and communicate whereas Odontocetes produce many more high frequency clicks and whistles used to locate prey on top of communication and navigation. Fifthly, Mysticetes have double blowholes (shown to the right) while Odontocetes have single ones. And lastly is their size! Odontocetes, with the exception of sperm whales, are generally much smaller than their Mysticete relatives. So, if you see a smaller marine mammal producing high frequency clicks, breathing through a single blowhole, eating larger prey like fish and squid, and smaller in size chances are it’s a dolphin!

Kopelman, A. H. (n.d.). CETACEANS. Retrieved October 27, 2016, from http://www.cresli.org/cresli/cetacean/cetapage.html

Locating Echolocation

Imagine playing hide and seek, now imagine being able to always find who ever your looking for without actually going out to find them.

Well Echolocation aka bio sonar is used to emit calls out in the environment. Sending sounds waves that reflect off of other organisms or objects allowing organisms to locate and identify. Organisms like Odontocetes such as dolphins use Echolocation in order to see. Other animals such as bats, birds and marine mammals use Echolocation to navigate or forage.

When dolphins or bats use Echolocation they send out clicks that sends out an echo which they can hear allowing the location of certain objects or organisms be found in an environment, this explains how Echolocation gets it’s name. Some scientists believed that this ability was developed slowly over time. Some of the animals that have the ability to echolocate usually are hunting in environments where it is difficult to use sight. For example, dolphins are in an environment where their pray camouflages with their environment or bury themselves in sand. They also are in an environment where the clarity is not always good so they have to be able to find prey and avoid predators. Bats are nocturnal animals that only come out at night where it is also difficult to use sight. Throughout time animals such as dolphins and bats slowly evolved by adapting to their environment in order to survive.

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For dolphins, the clicks that they send out pass through their melon (top part of head). The melon then acts as a lens that focuses the sounds waves and sends them out as a beam, which is the projected forward in the water in front of the animal. The sound waves bounce off of any other organisms or objects in front of the animals and come back as an echo. Sound waves travel in water at a speed of 1.5km/sec (0.9mi/sec). This is 4.5 times faster than sound traveling through air. There are different frequencies that the sounds can travel from. High frequency sounds do not travel far in water due to how long the wavelengths are and how great the energy is. However, low frequency sounds do travel farther which is why echolocation works best when the object or organism in front of the dolphin is about 5 to 200meters away (16- 656ft). Now this vary on how large the object or organisms they are looking for is also.

Echolocation is an amazing adaption that developed over time and is used by multiple organisms, maybe is a long time we also my develop and adaptation that is cool like Echolocation.

 

Sound in Water

Did you know that sound travels over four times faster through water than through air? Next time you poke your head underwater, notice how it is difficult to tell which direction sound is coming from – that’s because it’s traveling so fast that there is no time for you to notice which ear it hits first!

Sound travels so quickly through water because there is more “stuff” – or “medium” – to conduct the sound waves. Have you ever played the game “telephone”, where one person passes along a message to another, and so on? Think of five hikers standing one mile apart on a trail, versus a baseball stadium row full of people packed close together. If both groups try playing telephone, through which group will the secret message travel faster? Through the one with more members closer together – like water molecules!Phases of matterMolecules are more densely packed together in ocean water, a liquid, than in air, a gas. This allows sound waves to pass more quickly through water. “Ironically”, sound travels even faster through iron, a dense solid, than water!

Many marine animals like fish, dolphins, and whales communicate and navigate using sound. For example, fish make specific popping sounds to find members of their same species to school with. Dolphins use echolocation – bouncing sound waves off of objects to determine their shape and location – to navigate and hunt, while baleen whales sing elaborate songs to call to each other in complex communication rituals. There is even a “sound corridor” at the specific depth where the pressure, temperature, and salinity are perfect for conducting sound slowly over thousands of miles, from Australia to Bermuda, for example, which fin whales use to communicate with other fin whales far away.

Sound

Fin whales use the Deep Sound Channel to communicate with fin whales very far away. (Image credit: David Rothenberg, thousandmilesong.com)

Since so many marine organisms use sound to survive, they are also often very sensitive to it. A shark’s best sense, for instance, is not in fact its sense of smell but its hearing! As our oceans are absorbing the excess CO2 in the atmosphere and becoming more acidic, sound is actually amplified, so loud and persistent sounds such as military sonar are having harmful effects on animals that are sound-sensitive such as dolphins and whales.

A microphone that records sound underwater is called a hydrophone. This spring, scientists from Oregon State University and the National Oceanic and Atmospheric Administration placed a hydrophone at the deepest place in the ocean, the Mariana Trench, southwest of Guam. To listen to what they heard, visit http://www.npr.org/sections/thetwo-way/2016/03/04/469213580/unique-audio-recordings-find-a-noisy-mariana-trench-and-surprise-scientists.

Hydrophones

Scientists lower hydrophones into the water at a special mooring over the Marianas Trench (image credit: NOAA)

Ocean Echolocation

Echolocation is the emittance of sound and the reflection of vibrations off of an object back to the sender. This is commonly used by bats and dolphins! Dolphins release a high pitch click or snap sound that travels through the ocean in an effort to locate their food source. However some scientists do not agree about where the sound comes from.  “Some scientists suggest that sound is emitted from a nasal plug and that the shape of the melon is altered by muscles to focus sound.  Other scientists believe that the larynx emits sound and argue that echolocation focusing is achieved by bouncing sound off various parts of the skull.” (http://www.afsc.noaa.gov/nmml/education/cetaceans/cetaceaechol.php). The time it takes for a dolphin to send and receive this information varies depending on how far the vibrations have to travel back to the dolphin.

Here at CIMI we teach echolocation to students a few different fun ways. Jacque, a Toyon Bay CIMI Instructor, is seen teaching her students how echolocation works through the use of props such as the sample dolphin skull she is seen holding. Her students also participate in a fun game of echolocation! Four students are split up into dolphins and fish. The dolphins are blindfolded and will emit a sound, a clip or snap, and the fish will repeat that sound. It is the dolphins job to find the fish using “echolocation” or the repetition of their sound. Our students find out that it is a bit harder than they realized!

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