Wednesday, December 12, 2007
Buoys catch whales on tape Researchers seek clues to mammals' behavior
12 December 2007
Bangor Daily News
Bill Trotter
BAR HARBOR - Not long ago, members of Allied Whale would make summertime trips 20 miles out to sea to drop an underwater microphone over the side of a boat, then spend hours listening to whatever sounds the device picked up.
The idea was to listen for whales and to see whether the noises they made revealed anything about their behavior as they swam through the Gulf of Maine. The researchers might not have heard much, but they believed the accumulated recordings would prove worth the effort to get up early, spend the day out on the water, and then spend hours back on land listening to whatever underwater chirps and burbles may have been caught on tape.
But for the past two summers, the group has been making trips out toward Mount Desert Rock with a slightly different mission in mind. This fall, they tracked down the offshore coordinates of a previous trip, pushed a button on a remote-control device they had brought with them, and waited.
After a couple of minutes, something they were looking for broke the water's surface nearby. It wasn't a whale, however, or even another marine animal. It was an underwater recording device they had deployed months earlier and were picking up to take back to land.
Allied Whale, affiliated with College of the Atlantic, deployed two of these so-called "pop-up" buoys below the waves in 2006 and six this past summer. By leaving the self-contained recording units out at sea for months, researchers can record much more data - and in all sorts of conditions - than they could while trying to do it from a boat.
"[The buoys] are doing it constantly. They are recording at night and in bad weather," Sean Todd, senior scientist at Allied Whale, said recently of the buoy system. "In theory, we could have a buoy out there all winter. No one wants to go 20 miles out to sea in winter."
Bioacoustic equipment
The buoys were developed by scientists at Cornell University's bioacoustics research program. Each buoy consists of an external underwater microphone called a hydrophone that is hard-wired through a waterproof connection to recording equipment sealed inside the buoy. Housed inside a 17-inch-diameter glass sphere are acoustic communications circuitry, a hard drive for data storage and batteries, according to a description on the Cornell program's Web site.
Besides powering the recording equipment, the batteries also electrify a stainless steel wire that attaches each buoy to an anchor of burlap sacks filled with pea gravel. After researchers activate a remote signal from the surface, the batteries charge the wire, which corrodes from the electrical current and then breaks within five minutes. Each buoy can be programmed to surface at a certain time and has a fail-safe mechanism that burns the wire so it can resurface before the batteries run out of power. Each buoy has strobe lights and VHF beacon transmitters that are activated at the surface to help scientists track them down.
They are built to go as deep as three miles below the ocean surface, but according to Todd the ones used by Allied Whale come to rest about 300 to 400 feet down. This year, the college deployed two groups of three buoys each in the Gulf of Maine, one trio just north of Mount Desert Rock, about 20 nautical miles south of Mount Desert Island, and the other along Inner Schoodic Ridge, an underwater formation a few miles to the northeast.
"They are pretty robust things," Todd said of the buoys. "The Maine seafloor is quite rocky and craggy."
By sinking the devices to a few feet off the bottom, scientists can minimize interference from the ocean surface, which tends to be more noisy and where sound tends to propagate more than at lower depths, Todd said. To maximize the buoys' range, researchers try to set them so they have good horizontal exposure to one another and to the surrounding water.
Each of the buoys has a recording range of up to about five miles, he said. The buoys in each trio are laid out five miles apart in a triangular pattern. They do not record nonstop but instead turn themselves on and off periodically to conserve battery power.
Having multiple buoys at each site helps in many ways, according to Todd. It helps provide redundancy in case one of the buoys fails, and by comparing the strength of a recorded sound among the three buoys in each triangular array, researchers can determine where the source was when the sound was made.
"We want to know where the whales are," Todd said. "Eventually, we're hoping these buoys will indicate what kind of distribution of right whales is out there."
'An ambitious program'
The location of whales in the Gulf of Maine, especially of endangered right whales, has become a hot topic lately as federal regulators have imposed restrictions on where lobster fishing gear can be deployed. Whale advocates say underwater arcs of rope on lobster traps pose a hazard to diving whales, but fishermen argue that whales don't swim in the near-shore waters where most fishermen set their traps.
Allied Whale researchers have not yet triangulated the sounds they captured, however, because one buoy from each trio has yet to be recovered, according to Todd. One seems to be hung up on an underwater ledge and the other may have surfaced prematurely and floated away, he said. Researchers have printed contact information on each of the buoys and will pay a finder's fee to anyone who returns a missing unit.
The recovered buoys have been sent back to Cornell University, where the audio is extracted and then returned to Allied Whale. Researchers at Cornell will keep the buoys for the winter and then bring them back to COA for deployment in the spring.
Chris Tremblay, a COA graduate who now works in Cornell's bioacoustics lab, said recently that the recording buoys were first developed about 10 years ago. With the growth of the global economy and of marine shipping traffic, he said, the program has expanded so that more than 100 buoys are now being used for a variety of academic and applied technical projects in the Pacific and Atlantic oceans.
For example, pop-up buoys are being used to determine the frequency and behavior of marine species off Gloucester, Mass., where Excelerate Energy is hoping to construct an offshore LNG importation terminal, according to Tremblay.
"Their application is pretty varied," he said. "We are starting to get in the realm of fisheries management type of stuff."
Still, the study of marine mammal acoustics is considered a "new thing," he said. Tremblay gave credit to Allied Whale for being committed to the program and for being in the forefront of institutions looking to learn more with pop-up technology.
"It's an ambitious program," Tremblay said. "It's not cheap for a small organization to do."
Discoveries
Though only in its second year, the program already has helped Allied Whale researchers make some interesting discoveries, according to Todd.
Kaitlin Palmer, an undergraduate student at COA, found that most whales were recorded vocalizing at night and that one humpback whale in the area even "sang" - a phenomenon thought to happen only when they breed at their wintering grounds in the Caribbean.
Palmer received a NASA fellowship to continue her research through this past summer. She is expected to present data from the program later this month at a Society for Marine Mammalogy conference in Cape Town, South Africa.
In an e-mail, Palmer indicated she has cataloged 12 types of sounds made by humpback whales around the buoy sites. She said little is known about the sounds humpbacks make when away from their breeding grounds.
"August 2007 I spent on Mount Desert Rock observing humpback whales in hopes that when we get the pop-up data back I will be able to compare my behavioral observations to the acoustic recordings, thereby correlating specific sounds to known activities (feeding, breaching, traveling etc.)," Palmer indicated. "Even the simplest call is really quite amazing. When you listen to the recordings it seems that out of nowhere comes this eerie voice that cuts through the relative silence."
The buoy program has helped Julien Delarue, a COA graduate student from France, study whether there is any difference between the vocalizations of whales found in the Gulf of Maine and those found in the Gulf of St. Lawrence. If there is, it could prove that whales in the two water bodies belong to two distinct populations, according to Todd.
"He's looking for the equivalent of a dialect," Todd said. "The students have more than proven themselves [with their research]."
Allied Whale has decided to concentrate on whale research at Inner Schoodic Ridge and at Mount Desert Rock, and the pop-up buoy program is just one component of that, Todd said. The group also conducts sight surveys for whales during the summer and is trying to determine the concentrations in the two areas of whale food such as herring and krill.
Meanwhile, researchers are extracting the data from the devices and beginning to go through this year's audio looking for interesting patterns or events. A computer program that speeds up the playback time helps shorten the process, but it still is likely to take months to go through it all.
"We're just starting to look at the data now," Todd said. "It's extremely labor-intensive."
