The U.S. Navy is collaborating with private and governmental researchers in an effort to determine how sonar affects marine mammals.
Tracey Moriarty, chief of the Naval Operations Environmental Readiness Division, describes three recent field studies in a piece published Monday on the Navy News Web site.
One project, based in the Bahamas, involved tracking marine mammals — notably beaked whales — during battle group exercises. Before the exercises started, researchers were able to attach radio and acoustic “tags” to three Blaineville’s beaked whales, a Cuvier’s beaked whale and five sperm whales.
Beaked whales are believed to be especially sensitive to sonar. It was in the Bahamas that six beaked whales were found dead on the beach within 24 hours of a Navy exercise.
“The mere presence of these species on a Navy range is counterintuitive to the perception of beaked whale reactions to sonar,” the Navy’s David Moretti was quoted as saying. “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.”
Moretti is the principal investigator for the Marine Mammal Monitoring Program at the Naval Undersea Warfare Center in Rhode Island.
“The animals are moving in and out of here,” said Diane Claridge, director of the Bahamas Marine Mammal Research Organization, “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 (the Navy exercise).”
The working hypothesis is that the animals move off the training range during sonar exercises and then come back when the exercises are over, but researchers can’t be sure the returning animals are the same.
“I think the most important thing is that it’s still very early,” John Durban of the National Marine Fisheries Service said in Moriarty’s report. “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.”
A similar experiment in California was conducted with the assistance of Greg Schorr and Erin Falcone of Cascadia Research Collective, based in Olympia. By the way, Cascadia’s Robin Baird collaborated on a study published in June (PDF 832 kb) about the likelihood of beaked whales getting “the bends” when startled by sonar.
The third experiment, in the Mediterranean Sea, looked at the responses of whales to sound in an area where whales were unlikely to have been exposed to sonar in the past.
I’m looking forward to conclusions from all three studies, which are expected to be described in upcoming reports.
