Contributing Writer
Capt. Cathy Eagle
I have been boating our local waters for 48 years and doing charters for almost 30 years. I have never ‘heard’ a dolphin’s click or whistle while onboard, and trust me, I have encountered thousands of dolphins. Ironically, many onboard guests insist they hear the dolphin communicating and I am wondering, am I missing something?
It turns out, above water, the sound barrier between air and water muffles the dolphin’s vocalizations. Sound waves travel about 4.5 times faster in water than in air. About 99% of sound energy bounces off the surface of the water and does not transfer into the air. This natural barrier prevents most of the dolphins’ underwater clicks and whistles from reaching our ears on a boat or beach.
Typically, what you hear above water is the loud, rapid “chuff” or “whoosh” sound when dolphins surface to breathe. We also hear the loud smacks or cracks when a dolphin slaps its tail or flippers against the water. When a dolphin breaches the water, we will hear the sound of a dolphin jumping out of the water and landing on the surface.
Their high-frequency clicks and whistles, which are used for echolocation and communication, are completely ultrasonic and inaudible to humans above the water surface. Dolphins can hear humans above the water, but their hearing is highly adapted for an underwater environment.
Bottlenose dolphins have a highly advanced hearing range of 75 hertz to 150,000 hertz, allowing them to hear each other’s ultrasonic clicks and whistles. The healthy human hearing range spans from 20 Hz to 20,000 Hz. Most everyday human conversation occurs between 2,000 Hz and 5,000 Hz. Hertz is a unit used to measure frequency, which is the speed at which a sound wave vibrates.
To hear the full, complex range of the dolphin’s echolocation clicks and communication whistles, you need to listen from under the surface of the water.
Researchers and marine enthusiasts use specialized underwater microphones called hydrophones. Hydrophones are designed to detect and record acoustic signals underwater by converting underwater sound waves into electrical signals.
Hydrophones allow dolphin researchers to listen to and analyze dolphin communication and behavior.
The Sarasota Dolphin Research Program uses suction-cup hydrophones to link specific whistles to individual, known dolphins. This technology helps identify which dolphin is “speaking”, tracks synchronized behaviors, and helps figure out how vocalizations coordinate cooperative tasks.
Signature whistles develop and change as dolphins age. Initially, the young dolphin mimics its mother’s whistle, eventually developing its own whistle. Dolphins can identify each other’s whistles up to eight miles under the water. These highly specialized, unique vocalizations, allow dolphins to identify one another, locate pod members, and maintain social bonds which are critical to survival.
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Capt. Cathy Eagle
Captain Cathy Eagle has spent over 45 years boating on our local waters. As a professional Charter Captain, she specializes in Dolphin and Nature tours.
Capt. Cathy's Boat Tours
Matlacha, Florida
(239) 994-2572
www.CaptainCathy.com
