


In the waters off Dominica in the Caribbean, a drone descends from the sky toward a sperm whale. Instead of dropping a tag from above, this drone will press against the whale’s back to attach a specialized sensor. The tag’s suction cups will stick to the whale’s skin, allowing the device to record audio of these marine mammals communicating.
The technique, which researchers call tap-and-go, is described in a new study published in the journal PLOS One on Wednesday. The findings demonstrate that the approach is a possible way to gather vital scientific data while minimizing the disturbance to whales.
“This is definitely the future,” said Jeremy Goldbogen, a marine biologist at Stanford University who was not involved with the research. “It’s really exciting to see these new innovations,” he said.
Scientists have long used a traditional tagging method that involves standing on a boat’s prow and using a 20-foot pole to attach the tag to the whale. But the boat’s noisiness and proximity to the whales can cause them stress. The method also takes a lot of time and coordination, said Daniel Vogt, a research engineer at Harvard and the lead author of the study.
“We always wanted to improve this method,” he said of traditional tagging. Drones, in comparison, allow scientists to reach the whale from a distance, and more quickly. “We want to reduce the disturbance to the animal while improving the quality of the data that we collect,” Mr. Vogt said.
In recent years, drone technology has changed the way scientists study whales. Drones offer more than eyes in the sky: They can identify and measure individual whales, compare their behavior at the sea surface and even collect biological samples. By flying through the clouds of vapor, or “blow,” that whales emit when they surface to breathe, drones can gather information about the whale’s genetics, hormones and microbiomes.

Scientists have experimented with using drones to drop tags from about 30 feet above onto the backs of Rice’s whales, a species of baleen whale that has dwindled to less than 100 individuals remaining. Other research groups have dropped tags onto blue and fin whales from a lower height. The tags secure themselves with suction cups and the pressure that results from the whale’s dive.
Tap-and-go takes the idea one step further. It’s a “new and creative way to take advantage of what a drone can do,” said Ari Friedlaender, an ecologist at University of California, Santa Cruz, who was not involved with the study. “It just gives us a much better chance of being successful in our science if we have multiple ways of doing this,” he said.
Mr. Vogt and his team engineered drones that would withstand saltwater, wind currents and rough seas.
To test them, the researchers conducted trial runs on sperm whales, which can measure up to 60 feet long and dive deeply. A sperm whale spends only about eight minutes of a 45-minute dive at the surface, so tagging one at the right moment can be challenging.
Out of 20 tagging attempts, more than half proved successful. The entire operation, from aligning the drone with the whale to deploying the tag, took less than seven minutes.
The sensors can be used to study whale hunting patterns, acoustics and even social interactions. To date, the tags have been successful tools for studying many species of large whales, including minke, sperm, blue, humpback and North Atlantic right whales. The tags are designed to collect data for hours to days before automatically detaching from the whale. Researchers then recover the devices using telemetry or satellite messaging systems.

Mr. Vogt said he hoped the method would allow him and his team to deploy more tags and record more audio. He is a member of Project CETI (short for “Cetacean Translation Initiative”), an organization that investigates whether artificial intelligence can be used to decode whale songs. That undertaking requires large amounts of whale audio.
“The pole-based approach is still relatively noninvasive," Dr. Goldbogen said. But, he said, the drone method opens more possibilities for tagging species, like fin whales, that would otherwise be difficult to keep up with.
Dr. Goldbogen said, “This adds yet another method in our vast and diverse tool kit for how we study large whales in the open ocean — which is always a challenging thing.”