Boston, MA -- Myrtle, a 500-pound, 50ish green sea turtle and long-time New England Aquarium Giant Ocean Tank resident, is playing an instrumental role in an exciting hearing study. All species of sea turtle are either endangered or threatened, and little is known about sea turtle hearing. Data gathered will be used in the ongoing effort to learn more about sea turtles and determine if man-made sounds in the ocean are detrimental to sea turtles.
This is the first project to test and record hearing capabilities in sea turtles using "operant conditioning." Operant conditioning, a training method often used with marine mammals like seals and sea lions, encourages behavioral responses through positive reinforcement--like food. Myrtle is very responsive and interested in what goes on around her, making her a perfect candidate to help with this study. Myrtle remains unfazed by all the fuss.
For researchers to conduct a hearing test, Myrtle must learn to position herself comfortably at a particular station and stay there until she hears a tone. Tones of various frequencies are presented to her, and Myrtle is learning to indicate that she has heard a tone by touching a plexiglass circle. She's rewarded with fish, squid or lettuce for touching the circle when a tone is played and for staying at the station when no tone is played.
Funding for this two-year project comes from an Office of Naval Research grant totaling $120,000. New England Aquarium collaborators are Dr. Arthur Popper and Dr. Robert Dooling, both professors at the University of Maryland in College Park, Maryland. Dr. Popper has extensive experience studying hearing in fish and dolphins, and the anatomy and physiology of the auditory system. Dr. Dooling has conducted definitive studies of hearing by birds, and he has also developed several techniques widely used to conduct animal hearing studies.
At the New England Aquarium, Kathy Streeter, a marine mammal expert with 24 years of training experience, is the principal investigator. "It's been an education working with Myrtle," says Streeter. "But the project is challenging. Based on our work with sea lions and dolphins, we had to develop new training protocol and design the testing apparatus for use with a large sea turtle. We also had to modify the equipment to accommodate the Giant Ocean Tank exhibit and all the other animals living there. Plus, Myrtle is not as agile as a marine mammal. I have learned to be patient and watch carefully for Myrtle's reactions, which are very clear. I never would have thought a turtle would be so opinionated."
In the future researchers hope to determine if sounds can be used to help free-ranging sea turtles avoid fishing nets, a serious threat to turtles in the wild. The use of sound as an entanglement deterrent has proven successful (see Nature, August 7, 1997 and September 25, 1997).
The New England Aquarium is dedicated to strengthening society's relationship with the world of water through hands-on programs, live animal exhibits, and public lectures and forums on timely aquatic conservation issues.
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