Journalist 2nd Class Jessica B. Davis –
Professionals and students from the University of Hawaii (UH) are currently studying dolphin hearing and echolocation - the use of sound waves to "see" - to help the Navy improve mining and sonar techniques and make the oceans safer for marine mammals.
The research is being conducted through the joint Marine Mammal Research Program, located at Marine Corps Base Kaneohe Bay, Hawaii.
"We do research on hearing primarily because we're concerned about the loud sounds in the ocean and its effects on the animals," said Marine Mammal Program Director Dr. Paul Nachtigall. "We research echolocation because we're interested in duplicating the fine capabilities of the dolphins' echolocation."
Two bottlenose dolphins, BJ and Boris, and a false killer whale, Kina, are helping scientists better understand echolocation and hearing safety for marine mammals.
The dolphins at the research program are demonstrating just how valuable their sonar is. BJ is able to find a piece of metal through two feet of mud, and she's able to tell researchers whether it's brass or stainless steel. She does this by either touching a ball to indicate steel, or remaining motionless to indicate brass.
Boris has helped to develop a temporary threshold level for dolphins, giving the Navy a starting point to begin regulating operational sound.
The Office of Naval Research provides the majority of the funding, and also has an agreement with Marine Corps Base Hawaii's commanding general to use the base facility. The University of Hawaii provides the program with employees, volunteers and students. Besides conducting research, the facility is equipped with a complete laboratory, surgery, and necropsy facility for mammals that strand around Oahu.
"Stranded animals that come in are quite often very sick," said Kristen Taylor, UH zoology graduate student intern. "We take the animals to [Kaneohe Bay] where we can run tests, help them get better, and eventually release them. Their main sense is hearing, so we have to make sure it's good before we release them."
Researchers use a method similar to that used to measure human hearing.
"We play loud sounds for the animal to see what the effect is on their hearing and look for the small shift in hearing," Nachtigall said. "That shift gives us a benchmark of where to start to regulate the sound."
The Navy commits nearly $10 million annually in research to better understand how marine mammals hear and how they may be affected by manmade sound.
Seismic disturbances, snapping shrimp and sounds from other ocean dwellers, rain, lightning strikes, and manmade sounds such as offshore drilling, seismic surveys, commercial shipping and other ship sounds, fishing boats, recreational boating, and sonar use contribute to the background sound in today's oceans.
"[The dolphin's] bio sonar is just superb," Nachtigall said. "We're interested in the fact that [BJ] can do that, but we're much more interested in how she does that. So, we do experiments that look at the acoustics that tell us how she's able to do that. We build algorithms and pass that information on to the people who build sonar."
The Navy has established procedures to minimize the potential harm to marine mammals from sonar use, including monitoring for vocalizing animals with passive sonar and/or utilizing trained lookouts prior to commencing exercises.
Additionally, the Navy suspends sonar operations when there is a risk of harm to marine mammals.