Scientists to sea turtles: ‘Can you hear me now?’
Sea turtles can hear low frequency underwater sounds like shipping traffic and coastal construction, according to a new study by Mote Marine Laboratory.
The discovery is significant because permit criteria for proposed marine activities such as building and operating oil drilling or port facilities includes assessments of the impact on marine life, including whether construction and operation noise is likely to affect reproduction and feeding.
Researchers trained a loggerhead sea turtle named Montego to answer the question, “Did you hear that?” by touching a paddle with her beak if the answer was “Yes.”
Turtles have smaller brains than manatees, which have been trained at Mote to touch a paddle if they hear a sound.
But Montego, raised by humans in North Carolina and a Mote resident since 1998, eventually learned to answer, first learning to allow herself to be weighed and handled, then learning to swim to a target for a food reward.
For the hearing study, she learned to wait in place near a training platform where an LED light would flash to signal the start of a hearing test. She was rewarded if a sound played from an underwater speaker and she touched a paddle with her beak.
Scientists discovered that she could hear low frequencies of 50-800 Hertz, a small range compared to the human hearing range of 20-20,000 Hertz.
Now, Montego is helping Mote scientists study how well sea turtles can tell which direction a sound is coming from, particularly boat engines; like manatees, turtles often are injured from boat strikes.
Before the hearing study, turtle hearing tests consisted of auditory-evoked potential, or AEP, using sensors to measure the brain’s response to sounds, like hearing tests for human infants, according to Mote. Those tests indicated that at least three species of sea turtles hear some low frequencies.
The new study shows similar results, indicating that researchers can rely on the AEP test on turtles that are not trained.
Researchers from New College of Florida, the University of South Florida College of Marine Science and the University of Florida College of Veterinary Medicine also collaborated on the project.
The public can watch sea turtle training each weekday afternoon at Mote, open from 10 a.m. to 5 p.m. daily at 1600 Ken Thompson Parkway in Sarasota. Admission is $17 for adults, $16 for seniors over 65 and $12 for kids ages 4 to 12. Kids ages 3 and younger and Mote members are admitted free.
