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Listening for Humpback Songs Across the Open Ocean

Researchers are hoping to discover new travel routes of the Pacific humpback by utilizing a robot that monitors their unique means of long-distance communication.

The robot left the Big Island of Hawaii on January 15th, slowly sailing toward Mexico and on the prowl for humpback whales rarely seen on the high seas. On Tuesday, the seafaring bot named Europa arrived at the first seamount, an underwater mountain in the vast open ocean of the western Pacific, about halfway to its destination. But there have been no confirmed signs of whales so far.

Beth Goodwin hopes that will change soon, but she acknowledges the odds may be long.

Goodwin, director and vice president of Hawaii operations for the Jupiter Research Foundation—a non-profit dedicated to developing new research technologies, which also has an office in Los Altos, California—is leading the foundation's Humpback Pacific Survey (HUMPACS). The project sent Europa—an autonomous wave- and solar-powered vehicle called a wave glider—on a mission to find out if Pacific humpback whales roam the open ocean and, if so, establish their numbers and travel routes. For another month or two, Europa will keep propelling itself slowly forward while recording the sounds of the pelagic Pacific, including, perhaps, the humpback songs the massive marine mammals use to communicate with each other across vast distances. (You can track Europa's journey here.)

If humpbacks are found on the high seas, it might change our understanding of their behavior and migration patterns—important information that could be used to ensure protections for endangered populations. Current maps of humpback populations show that the whales congregate along coasts. They move north to feed in the summer and south to breed in the winter. But some of the feeding whales don't end up in the breeding grounds, Goodwin said. And there are other signs that some whales cross the Pacific between distinct populations. There may even be a "more continuous band" of humpbacks spanning the ocean, according to Goodwin. For instance, whales in all of the Pacific breeding grounds sing the same song despite being an ocean apart and not feeding in the same areas.

"Could there be spots between, in the deep water, that they're hanging out in, like the seamounts?" Goodwin asked. "Do they have messengers that go in between? No one really knows."

Finding that out could be critical to being able to effectively protect the habitat of humpbacks—and to understanding their population dynamics and genetics to better craft recovery plans. Two of the species' seven Pacific populations are listed as endangered and another as threatened.

But finding humpbacks in the open Pacific—even if they're there—won't be easy.

The glider, made by Liquid Robotics, a Silicon Valley-based company spun off from the Jupiter Foundation and later acquired by Boeing, consists of two parts. A seven-foot by two-foot surfboard-shaped float sits on the water's surface and houses solar panels, sensor arrays, and antennae. Tethered about 26 feet below the surface is a sub equipped with a rudder and louvered wings that twist to thrust the glider forward as the float is carried up and down along the waves.

Attached to the sub is a hydrophone, recording everything that happens within 10 miles of the glider.

"So we're hoping that a whale in the big vast ocean happens to swim within 10 miles of a wave glider," Goodwin said.

The glider is inching along at an average speed of about 1.5 knots an hour, which makes it unique, Goodwin said, as it conducts a first-of-its-kind, super-slow survey of the open ocean. (The gliders are collecting photographs and data on sea surface temperature in addition to the sound recordings.) "It's the difference between if you jog through the forest, what do you see versus if you walk through the forest," she said. "Or if you drive down the highway at 80 miles per hour versus if you walk down the highway," she added.

"It's pretty much a needle in a haystack, but fortunately humpbacks are a loud needle," she said. Humpback songs span a huge range of frequencies compared to other whales', making it, in theory, more likely a recording device will be able to pick them up.

Goodwin said that, if the gliders do pick up humpback sounds, we'll know there are some whales out there; if they don't, we won't really know one way or the other. "We would need a swarm of wave gliders for that," she said. "But we're going to where we think there might be a good chance. This really is an exploratory project."

Either way—and especially if humpbacks are found—the project will raise more questions that future research will have to answer.

"We know quite a lot in terms of destination, but not as much about the migratory routes" of humpbacks, said Scott Baker, associate director of Oregon State's Marine Mammal Institute and an expert in humpback population dynamics.

Baker, who is not involved in the Jupiter project, said the work is not likely to change population distribution maps much. "But it might make the borders or boundaries a little fuzzier. ... It could tell us what we're missing, potential components of the habitat that we're missing," he noted.

That could especially be the case if Europa finds that the frequency of humpback songs doesn't decrease as the robot moves farther away from Hawaii. "If there are lots out there in the middle of nowhere, then, a-ha, there could be more whales making horizontal migrations not just vertical migrations. And that is possible," Baker said, referring to the typical north-for-the-summer/south-for-the-winter whale migration pattern.

Those potential findings would also help conservationists and wildlife managers better understand and mitigate the dangers that humpbacks face. Whales along the coasts face risks of entanglement in fishing gear or boat strikes. "If whales are in the middle of the ocean that we're unaware of, there could be risks we're unaware of," Baker said. "It would give us information about habitat use or distribution that we're unaware of or that we are aware of but are underestimating right now."

That information will still be a way away. Goodwin and her team don't really know yet whether the frequency of whale songs has decreased as the glider has moved into open ocean because they can only get back 10-second clips of sound, which each take three to eight hours to download. "We're just sneaking a peek, just in case it hears something,"

This article originally appeared on Oceans Deeply, and you can find the original here. For important news about our world’s oceans, you can sign up to the Oceans Deeply email list.