USA — Navy Facility Studies Marine Mammal Behavior

WASHINGTON — The U.S. Navy is spon­sor­ing research that seeks to bet­ter under­stand how marine mam­mals respond to human-made under­sea sounds.

Some of that research is tak­ing place at Navy acoustic ranges like the Atlantic Under­sea Test and Eval­u­a­tion Cen­ter, or AUTEC, in the Bahamas. AUTEC’s research is spon­sored by the Chief of Naval Oper­a­tions Envi­ron­men­tal Readi­ness Divi­sion.

“The goal of our pro­gram is to study ani­mals in their nat­ur­al envi­ron­ment through the appli­ca­tion of pas­sive acoustics, which means we lis­ten for the vocal­iza­tions that are made by ani­mals and then try to use detec­tions of vocal­iza­tion as a proxy for the behav­ior,” said Dave Moret­ti, the prin­ci­pal inves­ti­ga­tor for marine mam­mal mon­i­tor­ing on the Navy’s ocean-lis­ten­ing ranges, in an April 21 inter­view on Pen­ta­gon Web Radio’s audio web­cast “Armed with Sci­ence: Research and Appli­ca­tions for the Mod­ern Mil­i­tary.”

AUTEC usu­al­ly employs hydrophones — lis­ten­ing devices sim­i­lar to under­wa­ter micro­phones — for track­ing sub­marines and oth­er under­sea vehi­cles. Now, the cen­ter is using hydrophones to lis­ten to under­sea crea­tures, like whales, Moret­ti said.

“We’re try­ing to take the infra­struc­ture of these facil­i­ties and apply it to pas­sive acoustics for the study of marine mam­mals,” he explained.

In March 2000, a group of beaked whales became dis­ori­ent­ed and strand­ed them­selves upon a beach near AUTEC. There are sev­er­al species of whales in the area where AUTEC is locat­ed, Moret­ti said, with beaked whales being the most preva­lent.

“At AUTEC, to our knowl­edge, there haven’t been any mass strand­ings of beaked whales …even though they use active sonar repeat­ed­ly through­out the year,” he said. Moret­ti defined mass strand­ing as when two or more adult mam­mals swim up onto a beach.

“[At AUTEC] you don’t have mass strand­ings even when sonar oper­a­tions take place,” Moret­ti said, “and it’s one of the things that we’re try­ing to tease out of the data, to try to under­stand why that is.”

Moret­ti said that ships are on the range at sched­uled times and are pre­cise­ly tracked. “The sen­sors are real­ly set up to track any­thing under the water, but any­thing on the sur­face is also tracked,” he said.

AUTEC has the abil­i­ty to cor­re­late data relat­ed to the ocean-going mam­mals with ves­sel traf­fic, Moret­ti said. “So now we can get a record of both ani­mal behav­ior and also a pre­cise record of ship tracks in open ocean waters,” he not­ed, “and in cas­es like the North­west Prov­i­dence Chan­nel, putting those data sets togeth­er is very, very dif­fi­cult.”

To ensure con­ti­nu­ity of data when the ani­mals are not vocal­iz­ing or out of range of the sen­sors, Moret­ti said, select­ed ani­mals are tagged with transpon­ders that allow satel­lites to track their move­ment. This is a coop­er­a­tive effort with rep­re­sen­ta­tives from the Nation­al Marine Fish­eries Ser­vice and the Bahamas Marine Mam­mal Research Orga­ni­za­tion. In addi­tion, he said, rep­re­sen­ta­tives from the Woods Hole Oceano­graph­ic Insti­tu­tion in Mass­a­chu­setts and St. Andrews Uni­ver­si­ty of Scot­land are assist­ing in the pro­gram.

Anoth­er type of tag used in the pro­gram is the D‑tag, a dig­i­tal recorder devel­oped at Woods Hole that pro­vides data on the pitch, roll, and depth of the animal’s move­ment.

“Those tags stay on about 19 to 20 hours,” Moret­ti said, “but they give very precise…very pris­tine data on the move­ment of ani­mals with­in that time span.”

Moret­ti explained that the data they are gath­er­ing has pro­vid­ed much need­ed insights into the pri­vate lives of whales, par­tic­u­lar­ly the elu­sive, deep-div­ing beaked whales.

“I think what peo­ple for­get is that we’re try­ing to study ani­mals in their nat­ur­al envi­ron­ment, but these ani­mals live in the deep ocean and they don’t come to the sur­face often,” he said. “It’s extreme­ly dif­fi­cult to study their behav­ior because it’s an envi­ron­ment we’re just not equipped to deal with well.”

Besides learn­ing about behav­ioral response of whales to man-made sound, Moret­ti said, the research also is designed to under­stand the health of the whales.

“We’d like these tools to evolve to the point where we can say some­thing about pop­u­la­tion health and there’s an effort under­way to start some pro­grams for the study of these ani­mals on a pop­u­la­tion lev­el,” Moret­ti said. “It’s actu­al­ly been dubbed the PCAD — Pop­u­la­tion Con­se­quences of Acoustic Dis­tur­bance — mod­el­ing,” he added, “but that’s in its infan­cy, actu­al­ly.”

Moret­ti said that com­ple­men­tary research is being con­duct­ed at a sim­i­lar Navy range off the coast of Cal­i­for­nia, with assis­tance from spe­cial­ists at Cas­ca­dia Research, Uni­ver­si­ty of Cal­i­for­nia, San Diego, and the Uni­ver­si­ty of Ore­gon. A third pro­gram is cur­rent­ly being devel­oped at the Pacif­ic Mis­sile Range Facil­i­ty off of Hawaii.

Moret­ti applaud­ed the coop­er­a­tive work of the var­i­ous fed­er­al offices and insti­tu­tions, stat­ing that the project required a broad range of exper­tise in marine acoustics, sig­nal pro­cess­ing, sta­tis­ti­cal mod­el­ing, marine biol­o­gy, and ani­mal behav­ior.

“It brings exper­tise togeth­er to help make sense of these data sets that are being col­lect­ed,” Moret­ti said, “and the data have pro­lif­er­at­ed out into sev­er­al oth­er stud­ies.”

The Navy’s lead­ers are try­ing hard to bal­ance the require­ments of mil­i­tary mis­sions with good envi­ron­men­tal stew­ard­ship, Moret­ti said.

“It’s to that end that we are fund­ed,” he said, “so hope­ful­ly with time, we’ll be able to give some under­stand­ing and some guide­lines for future envi­ron­men­tal com­pli­ance.”

U.S. Depart­ment of Defense
Office of the Assis­tant Sec­re­tary of Defense (Pub­lic Affairs)