In the Mediterranean Sea, a prototype whale-tracking system can use a sperm whale’s clicks to pinpoint its position in three-dimensional space with an accuracy of 30 to 40 meters—just a body length or two for these 16-meter-long whales. In tests using both artificial pings and sounds made by real whales, the researchers showed that the system can provide enough warning for a nearby ship to change direction or slow down when a whale is in its path. The system was developed by a team of biological and computational researchers based in Greece. Led by Emmanuel Skarsoulis, director of research at the Hellenic Foundation for Research and Technology, the team named their new tool the System for Avoiding Vessel Strikes with Endangered Whales (SAvEWhales). The name reflects the researchers’ hope that, if implemented, their system could reduce the main cause of mortality for endangered sperm whales in the Mediterranean – ship strikes. The design of SAvEWhales is quite simple. Near the Hellenic Trench, an underwater canyon five kilometers deep south of Crete, Skarsoulis’ team tied three buoys in a triangle one to two kilometers apart. Suspended from each buoy on a 100m line was a hydrophone to detect underwater sound. These three hydrophones raised whenever a nearby sperm whale clicked, which they do to locate prey. Skarsoulis and his colleagues developed a computer program to compare how long the sound took to reach each hydrophone, giving them a way to triangulate the whale’s location. But SAvEWhales’ secret weapon means it can do much more than spot a whale in a grid. While using boat-towed hydrophones to listen to sperm whales in previous work, one team member, Alexandros Franzis, noticed that every sperm whale click he heard seemed to repeat itself, like a ghostly echo of itself. Once Frantzis, the director of research at the Pelagos Cetacean Research Institute in Greece, discussed the problem with Skarsoulis, they found an explanation: the second click was the call of the sperm whale bouncing off the surface of the ocean. Using these reflections, the scientists built their algorithm to calculate the depth of the clicking whale. The deeper a whale is when it clicks, the greater the gap between when the initial click and the reflection reaches the hydrophone. Using the information from both clicks, the SAvEWhales system can detect a whale at a depth of up to 900 meters within 10 kilometers of the buoys. And by performing the same calculations every time a whale clicks nearby, scientists can actively track the whales as they swim. In the future, they could even use this system to warn ships that a whale is about to appear nearby and potentially prevent a collision. Experts see SAvEWhales as a useful addition to a growing field of passive whale watching systems. Christopher Clark, a bioacoustician at New York’s Cornell University who led the effort to create the Boston Harbor buoy network that automatically detects the calls of endangered North Atlantic right whales, applauds the innovation of receiving near-real-time information that will they could use the ships on the spot. He also emphasizes that sightings of sperm whales are few and far between in the Mediterranean, adding value to the system. Despite its promise, it may be some time before SAvEWhales, or something similar, is in permanent use. So far, the system has undergone only a two-year pilot test, and Skarsoulis and his colleagues have already identified some obstacles to expanding it into a full-time monitoring system. These include analytical challenges, such as the difficulty of differentiating individual whales when a group travels together. There are also logistical hurdles involved in maintaining a system at sea, which faces constant wear and tear from salt, sun and storms. In fact, fishermen who happened to be nearby watched the first two deployed SAvEWhales buoys disappear underwater, swept away by strong currents during a typhoon. Skarsoulis hopes that one day the system could be a permanent cable observatory. However, there are also limits to how widely applicable such a system could be. The surface reflectance analysis that makes SAvEWhales so powerful cannot be used for whales that communicate through songs rather than clicks, such as fin whales, which are also endangered in the Mediterranean. There is one final obstacle that is unique to this day and age. After the project’s initial prototype period, Skarsoulis, on February 23, submitted a proposal to the Greek Ministry of Environment and Energy to operate a single buoy off Crete so his team could track how many sperm whales passed through the area. The next day, Russia invaded Ukraine, starting an international energy crisis. It’s “important to note that it was the Ministry of Environment and Energy,” Skarsoulis points out, ironically suggesting that enthusiasm for spotting whales can get in the way of oil exploration. His proposal has not been heard from since. However, such monitoring is urgently needed in the Mediterranean Sea, says Nino Pierantonio, a whale researcher at the Tethys Research Institute in Milan, Italy. Ship strikes are responsible for more than half of sperm whale deaths in the region. Furthermore, because Mediterranean sperm whales are genetically different from those in the North Atlantic, this population is particularly vulnerable. Pierantonio notes that the risk is particularly high around the Hellenic Trench, a place rich in marine life and a sperm whale hotspot. The area is favored by groups of mother whales with calves, who spend much more time on the surface. Pierantonio says other efforts to reduce ship strikes, such as requiring vessels to slow down for whale feeding spots and changing shipping lanes, will also be necessary tools to protect the Mediterranean’s threatened whales. “When changing course and reducing speed is not an option, we need another way to alert vessels to the presence of whales,” he adds.
