How Dolphins Use Sound: Elementary

Developed by K. Schneider & W.K. Adams

Students learn about people and animals that use echolocation and how it works through video and discussion with their peers.

This activity can stand-alone or be done with other lessons in the echolocation unit. It can be used as a supplement for before, during, or after the echolocation unit.

Grade Level

1-12

Clean-Up

5 minutes

*The amount of time spent on this lesson depends on whether you’ve already taught the Doppler Effect lesson, and on how long you spend discussing the various jobs in acoustics.

Learning Goals

Students will be able to:
• Explain and provide examples of how humans can use echolocation
• Define an echo
• Define SONAR and Echolocation and give examples of several animals that use these tools
• Describe how far and what size objects dolphins can echolocate
• Describe different methods of dolphin communication

Materials not in Kit

Computers*
Presentation equipment

*It’s best if all students have an opportunity to use a computer to experience the website resources. If it isn’t possible, you can demonstrate and make it interactive.

Set-Up

Set-up the presentation with the PowerPoint or PDF slides and open the videos and links to make sure everything works.

Introduce the Activity

Explain that you will be going through a presentation that talks about echolocation and SONAR, and shows how dolphins use sound.

Echo Introduction
1. Ask the students the following questions:
→ Have you heard of echoes?
→ What are echoes?
→ What causes echoes?

2. Describe what an echo is
• An echo is when sound hits an object and then bounces back.
• When we hear an echo, we hear the bounce.
• In the image, the blue wave travels towards the barrier and hits. The red shows the wave bouncing back towards us.

3. Discuss the idea of echoes with the students:
→ Where are some places that we can find echoes?
→ Who uses echoes?

Bat, Dolphin and Whale Communication

1. Go to dosits.org and choose the “Audio Gallery.” Then select “Humpback Whale” and scroll down to the video of humpback whales off the coast of Hawaii.
2. Ask the class to decide if they can see or hear the whales easier.
3. After watching the video and they decide if they can hear or see the whales better, show the video again to ensure that everyone understands.
   • You can always hear the whales, but it is difficult to see through the murky water. The sound travels well through water, but our eyes can’t pick up the images as clearly.

Types of Dolphins
Scientists all agree that dolphins communicate with one another by using sounds and body language.

Dolphins and porpoises are the smallest toothed whales. Discuss the following types of dolphins:

Bottlenose Dolphins – Bottlenose dolphins, like Flipper the TV star, are the most familiar

Oceanic Dolphins – Including orcas and pilot whales, there are 32 species of oceanic dolphins

River Dolphins – There are 5 species of river dolphins

Porpoises – There are 6 species of porpoises
All dolphins are porpoises, but orcas and beluga whales are also porpoises.

Dolphin Communication

1. Ask the class to explain to each other how people recognize different people’s voices.
2. Discuss the ways dolphins communicate with each other:
   • Clicks and Whistles are the two main types of dolphin vocalization
   • Each dolphin has its own “signature whistle”
   • A “signature whistle is a series of whistles (like a dolphin Morse code) distinct from any other member of the group
   • Dolphins recognize each other’s whistles
3. Ask the class if they’ve heard of echolocation before, and if they know what it is. Echolocation refers to an ability that enables bats, dolphins and whales to essential “see” with their ears by listening for echoes. This helps these animals find and capture food.
4. These animals echolocate by producing clicking sounds and then receiving and interpreting the resulting echo.
5. Dolphins produce directional clicks and trains. Each click last about 50 to 128 microseconds.

Dolphin Echolocation:
• Sound waves travel 4 times faster through water – much faster than sound travels through air!
• These sound waves bounce off objects in the water and return to the dolphin in the form of an echo.
• This is similar to the sound simulation we tried earlier which showed how sounds hit the barrier and bounce back.

Click Trains
1. Go to dosits.org and select “Sperm Whale Removing Fish from Line.”
2. Ask the group to figure it out:

→ What happens to sound as they get closer?

You may need to play this video more than once. Help students understand that the clicks get faster as the whale gets closer (to narrow location) and the whale can clearly see, but he is also using echolocation.

NOTE: the video camera is on the bottom of the fishing line looking up. The whale isn’t stuck, he’s just holding on with his teeth.)

How Far Can a Dolphin Echolocate?

1. If you’ve already done the Echolocation Part 1 activity (middle school) or Echolocation Speed of Sound (lower elementary), have the groups think back and recall what was hardest, what they could and could not do when only using sound compared to sound and sight.
2. Tell the class that some dolphins can use echolocation to detect a 15 centimeter (6 inch) long fish a football field away!

• High frequency sounds don’t travel far in water
• Low frequency sounds travel farther because of their longer wavelength and greater energy
• Echolocation is most effective at close to intermediate range because dolphins and whales use high frequency sounds
• Their range is about 5-200 meters for targets 5-15 centimeters in length. This would be like clearly identifying a banana from 2 football fields away!

Echolocation vs. Sight

1. Discuss the fact that dolphins and bats are not actually blind, but use echolocation as their primary tool. Whales and dolphins do see better than bats.
2. Despite the effectiveness of echolocation, studies show that a visually-deprived dolphin takes more time to echolocate on an object than a dolphin using both vision and echolocation.

Common Dolphin Sound Clips

1. Go to http://dosits.org/galleries/audio-gallery/marine-mammals/toothed-whales/sperm-whale/ and listen to the two sound clips from the presentation.
2. Ask the class the following questions and let them discuss amongst themselves.

→ What did you hear in each sound clip?

→ What did you hear in each sound clip?
→ How are the two sounds different from each other?

Dolphin Communication/Sounds
Discuss the different methods dolphins have of communicating:

• Dolphins produce non-verbal sounds by slapping a body part against the surface of the water, which makes both a sound and a splash. Tail or fluke slapping is also common.
• Kerplunks are another non-vocal sound made by the tail. Other parts of the body used to produce noise in a slapping manner are pectoral fins and the whole body.
• Finally, jaw claps are made either above or underwater.

Key Lesson Terminology

Echoes – reflections or repetitions of sound waves. Echoes can be produced and heard by clapping hands or shouting in a large empty room with hard walls or in a cave for example.

Echolocation – a method used to detect objects by producing a specific sound and listening for its echo.

SONAR – Sound Navigation And Ranging, is the process of listening to specific sounds to determine where objects are located.

Clicks and Whistles – the two main types of dolphin communication.

Optional Extensions

Read 2-3 career profiles to the class and have them answer the following questions:

→ What’s in common regarding what they do as scientists?
→ What’s in common about the advice they give to students?
→ How do these scientists get to where they are today?

After the students have looked at the profiles, discuss them with the class.