[MARINE_BIOLOGY_INTERNATIONAL] Despite their lack of visible ears, Mote scientists prove sea turtles can hear


Despite their lack of visible ears, Mote scientists prove sea turtles can hear

Despite having eardrums that are covered up by their skin, Mote scientists have discovered that sea turtles are able to hear low-pitched sounds.

By Summer Smith, Reporter
Bay News 9
Tuesday, August 21, 2012


Mote scientists are conducting behavioral hearing tests on sea turtles for the first time in history.

This recent study, led by Mote and including collaborators from New College of Florida, the University of South Florida College of Marine Science and The University of Florida College of Veterinary Medicine, is helping everyone understand the hearing abilities of sea turtles, a threatened and endangered species whose ocean habitat is filled with natural and man-made sounds.

"So with the study we've determined that they hear low frequency sound levels," said Holly West, the Sea Turtle Care Coordinator at Mote Marine Laboratory.

West said despite having eardrums that are covered up by their skin, they have discovered the turtles are able to hear low-pitched sounds.

She said up until recently, the only way they could tell this was by using sensors to measure a turtle's brain response.

Now, scientists at Mote have trained two nearly 200-pound loggerhead sea turtles named "Montego" and "Shelly" to answer the question: "Did you hear that?"

While the turtles are not talking, what is remarkable is that they can indicate if they hear something or not.

The turtles have learned to touch a special response paddle with their beaks every time they hear a sound.

Results show the turtles can hear sounds ranging from 50 to 80-hertz.

"With increasing noise out in the water we want to learn more about it so we can apply it to the wild population and see if they can hear the boat noise and oil drilling out there," said West.

"A lot of people thought you could not train a sea turtle, at least not to the level needed for a behavioral hearing test," said Kelly Martin, the Mote scientist who led the study for her master's thesis at the USF College of Marine Science. "But, with a lot of practice, Montego was able to pick up this complex task."

How scientists trained sea turtle Montego

According to Mote, Montego, born in 1977, was raised under human care in North Carolina and in 1998 found a new permanent home in The Aquarium at Mote.

Several resident animals at Mote participate in groundbreaking studies focused on their hearing, sight, touch and other senses, with the goal of providing new knowledge to help resource managers conserve threatened and endangered marine life.

Mote's resident manatees have participated in sensory research for nearly 15 years, and the training techniques pioneered with them helped provide a basis for training sea turtles.

In 2006, Martin and her colleagues trained Montego for behaviors designed to make her health care run as smoothly as possible, including allowing her to be weighed and handled, along with swimming to a special target for a food reward.

In 2007 Montego learned more complex behaviors to participate in the year-long hearing study, which began in 2008.

Martin and collaborators trained Montego to wait at her target near a training platform, where an LED light would flash to signal the start of a research trial.

Then either a sound would play from an underwater transducer or nothing would happen.

Montego was trained to touch a special response paddle with her beak when she heard the sound and to do nothing if there was silence.

When she got the answer correct, she received a food reward. Montego was tested with sounds at different frequencies and varying volumes to find the limits of her hearing.

Results showed that Montego could hear sounds ranging from 50-800 Hertz, with her strongest hearing ability around 100 Hz. This is a fraction of the human hearing range, which covers 20-20,000 Hz.

Scientists also tested Montego with AEP, which yielded results closely aligned with the behavioral test.

How sounds affect sea turtles

It's new research scientists are hoping will lead to more turtle lives saved in the wild.

"Maybe most of them could get out of the way of boats and boaters can be aware of them as well," said Bruce Bragg, a visitor at Mote.

"This suggests that AEP is promising for testing the hearing range of other turtles that have not gone through a time-consuming training process, and it confirms findings that sea turtles have low frequency hearing," Martin said. "This hearing range includes noises that you find with shipping traffic, coastal construction and other human activities. Now we need to know how those sounds might affect sea turtles in the wild."

"The ocean is not a quiet environment, so to be able to apply this to a wild population of sea turtles, we want to know how well these turtles can hear sounds when man-made noise is present in the background," West said. "It's also important to know if they can tell where sound is coming from, especially as it relates to boat-engine noise. A lot of sea turtles end up with injuries from boat strikes, so it's important to know if they have trouble hearing where the boats are."

West and her team are now testing how well sea turtles can hear sounds over background noise, and they are currently analyzing findings.

Their next project will test how well sea turtles can sense the direction of sounds.

"I think the research training at Mote should be an example for others, it's great to have an aquarium that not only gives sea turtles a permanent home and educates people about them, but also works with them to learn something new," said Martin.

Mote exhibit

The public can watch Mote's sea turtles being trained each weekday afternoon.

Check for specific times at Mote's exhibit Sea Turtles: Ancient Survivors.

The Aquarium at Mote is open from 10 a.m. - 5 p.m, 365 days per year at 1600 Ken Thompson Parkway in Sarasota.

Admission is $17 for adults, $16 for seniors over 65 and $12 for kids ages 4 through 12.

Kids age 3 and younger and Mote Members always get in free.

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