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News | Aug. 10, 2009

Navy Continues its Commitment to Science through Marine Mammal Studies

By Tracey Moriarty Chief of Naval Operations Environmental Readiness Division

The U.S. Navy and its partners recently completed two studies that monitored marine mammal responses to military exercises.

The studies were conducted April 20-May 20 on the Atlantic Undersea Test and Evaluation Center (AUTEC) in northern Bahamas, and July 15-July 28 on the Southern California Offshore Range (SCORE) off Coronado, Calif. Both studies used small dart tags with satellite transmitters to track the movements of whales before, during and after unit-level and larger battle group exercises that included the use of active sonar. Additional data is being collected during biological and behavioral studies of marine mammals in the western Mediterranean Sea project currently underway off the Spanish Mediterranean coast and in the Tyrrhenian Sea to the west of the Italian mainland.

"These studies are a major focus of the Navy's marine mammal research program, which is designed to understand the effects of anthropogenic sound on marine mammals," said Dr. Frank Stone, Navy's marine mammal program manager. "Follow-on studies are planned at AUTEC and SCORE, as well as the Navy's other at-sea ranges over the next five years." 

Atlantic Undersea Test and Evaluation Center, Bahamas
The AUTEC study took place during a Submarine Commanders Course (SCC) and was performed by scientists from Naval Undersea Warfare Center (NUWC), the Bahamas Marine Mammal Research Organisation (BMMRO) and the The National Oceanic and Atmospheric Administration (NOAA) Fisheries Southwest Fisheries Science Center. David Moretti, principal investigator for NUWC's Marine Mammal Monitoring Program, led the Navy's effort to use AUTEC hydrophones to help determine behavior of whales on the range with and without active sonar present.

"The hydrophones are used to listen for vocalizations from the animals," Moretti said. "Over the years we've been able to detect those animals, send trained observers to their locations and identify them. It has enabled us to associate vocalizations with particular species."

Moretti and his team monitored a screen display of 93 hydrophones on the 500 nautical mile AUTEC range. When a hydrophone detected vocalizations, the NUWC team would contact the researchers waiting on the University of Miami's vessel, F.G. Walton Smith, and give them an approximate location of the whale. The research team would then race to the proposed location in hopes of deploying satellite tags and for photo-identification and biopsy work.

John Durban and Bob Pitman of NOAA Fisheries Southwest Fisheries Science Center worked with their Bahamian colleagues on the tagging effort, made difficult by unpredictable weather conditions. This collaboration successfully deployed nine satellite tags on three different species on and around the AUTEC range, including three Blaineville's beaked whales, a Cuvier's beaked whale and five sperm whales. Biopsy samples were also collected to obtain information on the genealogy, population structure and diet of the whales.

Scientists believe that beaked whales are sensitive to sound. 

"The mere presence of these species on a Navy range is counterintuitive to the perception of beaked whale reactions to sonar," said Moretti. "Given that this is an active Navy range where sonar is used, you wouldn't anticipate this species to be present in this particular location if you believed the popular press."

Diane Claridge, director of BMMRO, was already leading a multi-year study to observe the distribution, abundance and population structure of beaked whales in the northern Bahamas. The timing of this year's survey happened to overlap with the SCC.

"From working at AUTEC for previous projects, we have been photo identifying beaked whales in that area," she said. "The animals are moving in and out of here, and one of the things I'm interested in is whether or not that movement is related to the activities taking place such as the SCC." 

Though the team is still reviewing the data for this project, beaked whale monitoring during previous SCC events has shown a decline in acoustic detections of beaked whales during active sonar exercises. Beaked whale detections increased following the end of the multi-day exercise, leading to a hypothesis that animals moved off the range during exercises. However, this hypothesis remains to be tested, and the extent and distance of any movements remain unknown.

"We believe they avoid the sonar by moving off the range, and they return after operations are finished," said Moretti. "We have opportunistic data based on acoustics that supports that idea. Once they're off the sensors we really don't know where they go. I can't say definitively that the animals that leave the range are actually the same animals that come back."

The AUTEC study hopes to answer some of these questions.

"I think the most important thing is that it's still very early," said Durban. "Like any study, it's tempting to want results straight away, but often the key results are only obtained from continued long-term monitoring of abundance and movement patterns. Only by having that background monitoring data can you detect any key responses. So in some sense, we've just started, but it's been a good start."

Claridge agrees. 

"We're really on the cusp of what we're going to learn because we're just getting into the analysis of all survey data."

Researchers intend to return to AUTEC prior to the SCC event scheduled later this fall.

Southern California Offshore Range
On the West Coast, the SCORE Marine Mammal Research Project involved collaboration between NUWC, SCORE, NOAA Fisheries Southwest Fisheries Science Center, Cascadia Research and Scripps Oceanographic Institution. Whales on the instrumented Southern California Antisubmarine Warfare Range (SOAR) are monitored on 83 hydrophones mounted on the ocean floor at an average depth of 2,000 meters. Like AUTEC, the phones are used to monitor an area in excess of 500 square nautical miles. Cetaceans are photo-identified, biopsy sampled and electronically monitored to examine their response to military exercises.

The on-water tagging effort is led by Cascadia Research Collective's Greg Schorr and Erin Falcone. 

"We are experiencing success tagging species in this region, especially beaked whales - beyond what we initially thought possible," said Falcone. "The combined experience of collaborators on this project, from this and other regions, is allowing for continuous improvement in our data collection."

Eight animals were successfully tagged in eight days during fieldwork in July, including a Cuvier's beaked whale, bottlenose dolphin, Risso's dolphin and five fin whales. These tags supplement data collected from one Cuvier's beaked whale and three fin whales tagged at SCORE in 2008.

High Frequency Acoustic Recording Package (HARP) buoys, developed by John Hildebrand and Sean Wiggins at Scripps, help to monitor locations of the animals off range. By combining these data from the multi-sensor SOAR range, satellite tags and HARP buoys, the spatial and temporal distribution, movements and vocal behavior relative to active operations is being investigated. 

"With each study, we're moving closer to answering the big questions relating to health of populations," said Moretti. "We've made great leaps in knowledge from when the Navy started studying beaked whales 10 years ago. Back then we didn't even know what they sounded like, let alone the nature of their vocalizations. We now have preliminary data predicting how these animals move in sites of intense study, which we are beginning to interpret in an effort to answer those big questions."

When researchers return to SCORE this fall, they will be testing a new "fast and light" weather dependent model for studying beaked whales in offshore waters of the Pacific, which frequently experience high wind and swell conditions. Beaked whale dives can last more than an hour, with the animals only surfacing briefly and keeping a very low profile. Because of this, any unfavorable weather compromises the researchers' ability to locate and tag the animals. The "fast and light" model will mobilize researchers more quickly in favorable weather conditions to increase the amount of data collected. 

Mediterranean Sea
Unlike the SCORE and AUTEC studies, the Mediterranean tests are being conducted through controlled exposure experiments, in which the animals' behavior is measured before, during and after specific sound exposures planned by the researchers, rather than sonar sounds generated during naval exercises. Researchers for this project, referred to as MED-09, include representatives from the NATO Undersea Research Centre, Woods Hole Oceanographic Institution (WHOI), Genoa Aquarium and several other international scientific and academic organizations.

The researchers are studying whales with tags that can record sound, animal orientation and depth measurements. These "Dtags," short for "digital acoustic recording tags," were developed by WHOI and are invaluable in the study of beaked whales and other species that dive deep and seldom visit the sea surface. Dtags are attached using non-invasive suction cups.

"In MED-09, we're duplicating the experiments from 2007's behavioral response study at AUTEC," said Moretti. "The difference is that unlike the AUTEC animals, these animals are nave to sonar. We don't know if they'll behave the same way as animals that are accustomed to sonar exposure."

The scientific results expected from MED-09 will contribute to a greater understanding of marine mammal biology and oceanographic features in the western Mediterranean. The data will be provided to local and regional government, conservation and educational organizations to increase public awareness and appreciation of these areas and species. Specialized information obtained regarding the baseline behavior of beaked whales and their response to manmade sounds will be integrated into ongoing Navy environmental planning for exercises and also be made available to science organizations worldwide to support their research efforts. 

MED-09 began in late July and lasts until early September.