Sperm whales spend, on average, 10 minutes of every hour on the surface, presenting challenges for researchers studying them. | Source: Project CETI
In the chilly waters off the New England coast, researchers from the Cetacean Translation Initiative, Project CETI, can spend hours searching and waiting for an elusive sperm whale to surface. During the minutes the whales spend above water, the researchers need to gather as much information as possible before the animals dive back beneath the surface for long periods.
With one of the widest global distributions of any marine mammal species, these whales are difficult to track down, and even more difficult to learn from. Project CETI aims to use robotics and artificial intelligence to decode the vocalizing of sperm whales. It recently released research about how it tracks down sperm whales across the wide ocean.
“The ocean and the natural habitat of the whales is this vast place where we don’t have a lot of infrastructure, so it’s hard to build infrastructure that will always be able to observe the whales,” said Stephanie Gil, an assistant professor of Computer Science at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and an advisor on the project.
The project brings together some of the world’s leading scientists in biology, linguistics, robotics, and more. The founder of Project CETI, David Gruber, estimated that it’s one of the largest multi-disciplinary research projects active today.
“Project CETI was formed in March 2020, and we’re now over 50 scientists across eight different disciplines,” he said. “I think we’re over 15 institutions, which I believe puts us as one of the most interdisciplinary, large-scale science projects that’s ever been conducted. It’s incredibly rewarding to see so many disciplines working together.”
The researchers at the nonprofit organizationhave developed a reinforcement learning framework that uses autonomous drones to find sperm whales and predict where they will surface. The paper, published in Science Robotics, said it’s possible to predict when and where a whale may surface using various sensor data and predictive models of sperm whale dive behavior.
This new study involved various sensing devices, such as Project CETI aerial drones with very high frequency (VHF) signal sensing capability that use signal phase along with the drone’s motion to emulate an “antenna array in the air” for estimating the direction of pings from CETI’s on-whale tags.
“There are two basic advantages of [VHF signals]. One is that they are really low power, so they can operate for a really, really long time in the field, like months or even years. So, once those small beacons are deployed on the tag, you don’t have to really replace the batteries,” said Ninad Jadhav, a co-author on the paper and a robotics and engineering Ph.D. student at Harvard University.
“The second thing is these signals that these tags transmit, the VHF, are very high-frequency signals,” he added. “They can be detected at really long ranges.”
“That’s a really huge advantage because we never know when the whales will surface or where they will surface, but if they have been tagged before, then you can sense, for example, simple information such as the direction of the signal,” Jadhav told The Robot Report. “You can deploy an algorithm on the robot to detect that, and that gives us an advantage of finding where the whales are on the surface.”
“Sperm whales are only on the surface for about 10 minutes every hour,” said Gil. “Other than that, they’re diving pretty deep in the ocean, so it’s hard to access information about what the whales are actually doing. That makes them somewhat elusive for us and for science.”
“Even we humans have certain patterns day to day. But if you’re actually out observing whales on a particular day, their behavior is not going to exactly align with the models, no matter how much data you’re using to make those models right. So it’s very difficult to really predict with precision when they might be coming up,” she continued.
“You can imagine, if [the scientists] out on the water for days and days, only having a few encounters with the whales, we’re not being that efficient. So this is to increase our efficiency,” Gruber told The Robot Report.
Once the Project CETI researchers can track down the whales, they must gather as much information as possible during the short windows of time sperm whales spend on the surface.
“Underwater data collection is quite challenging,” said Sushmita Bhattacharya, a co-author on the paper and a computer science and robotics Ph.D. student at Harvard University. “So, what is easier than underwater data collection is to have data collected when they’re at the surface. We can leverage drones or shallow hydrophones and collect as much data as possible.”
At the center of the research is the Autonomous Vehicles for Whale Tracking And Rendezvous by Remote Sensing, or AVATARS framework. AVATARS is the first co-development of VHF sensing and reinforcement learning decision-making for maximizing the rendezvous of robots and whales at sea.
“We tried to build up a model which would kind of mimic [sperm whale] behavior,” Bhattacharya said of AVATARS. “We do this based on the current information that we gather from the sparse data set.”
Being able to predict when and where the whales will surface allowed the researchers to design algorithms for the most efficient route for a drone to rendezvous with—or encounter—a whale at the surface. Designing these algorithms where challenging on many levels, the researchers said.
“Probably the hardest thing is the fact that it is such an uncertain problem. We don’t have certainty at all in [the whales’] positions when they’re underwater, because you can’t track them with GPS when they’re underwater,” Gil said. “You have to think of other ways of trying to track them, for example, by using their acoustic signals and an angle of arrival to their acoustic signals that give you a rough idea of where they are.”
“Ultimately, these algorithms are routing algorithms. So you’re trying to route a team of robots to be at a particular location in the environment, in the world, at a certain given time when it’s necessary to be there,” she told The Robot Report. “So this is analogous to something like rideshare.”
Before bringing the algorithms into the real world with real whales, the team tested them in a controlled environment with devices the team put together to mimic whales.
We mimicked the whale using an engineered whale,” recalled Bhattacharya. “So basically we used a speed boat, and it had a loud engine. We used that engine noise to mimic the whale vocalization, and we had it move to mimic whale motion. And then we used that as our ground test.”
A customized off-the-shelf drone flying to deploy a whale tag developed by Project CETI researchers. | Source: Project CETI
“Every day was a challenge when we were out on the boat, because this was for me, and my co-author Sushmita, the first time we were deploying real autonomous robots from a boat in the middle of the sea trying to collect some information,” Jadhav said.
“One of the major challenges of working in this environment was the noise in the sensor,” he continued. “As opposed to running experiments in the lab environment, which is more controlled, there are fewer sources of noise that impact your experiments or your sensor data”
“The other key challenge was deploying the drone itself from the board,” noted Jadhav. “I remember one instance where this was probably the first or second day of the second expedition that we went on last November, and I had the drone ready. It had the payload. It was waterproof”
“I had already run experiments here in Boston locally, where I had an estimate of how long the drone would fly with the payload. And then we were out on the boat running some initial tests, and the drone took off,” he said. “It was fine, it was doing its thing, and within a minute of it collecting data, there was a sudden gust of wind. The drone just lost control and crashed in the water.”
The team also had to try to predict and react to whale behavior when performing field tests.
“Our algorithm was designed to handle sensor data from a single whale, but what we ended up seeing is that there were four whales together, who were socializing,” Jadhav said. “They were diving and then surfacing at the same time. So, this was tricky, because then it becomes really hard for us on the algorithm side to understand which whale is sending which acoustic signal and which one we are tracking.”
While Project CETI works closely with sperm whales and other sea life that might be around when the whales surface, it aims to leave the whales undisturbed during data collection.
“The main concern that we care about is that even if we fail, we should not harm the whales,” Bhattacharya said. “So we have to be very careful about respecting the boundaries of those animals. That’s why we are looking at a rendezvous radius. Our goal is to go near the whale and not land on it.”
“Being minimally invasive and invisible is a key part of Project CETI,” said Gruber. “[We’re interested in] how to collect this information without interacting directly with the whale.”
This is why the team works mostly with drones that won’t disturb sea life and with specially developed tags that latch onto the whales and collect data. The CETI team eventually collects these tags, and the valuable data they contain, after they fall off the whales.
“A lot of times, people might think of robotics and autonomy as a scary thing, but this is a really important project to showcase that robots can be used to extend the reach of humans and help us understand our world better,” Gil told The Robot Report.
This latest research is just one step in Project CETI’s overarching goal to decode sperm whale vocalizations. In the short term, the organization plans to ramp up data collection, which will be crucial for the project’s long-term goals.
“Once we have all the algorithms worked out, a future outlook is one where we might have, for example, drone ports in the sea that can deploy robots with sensors around the clock to observe whales when they’re available for observation,” Gil said.
“We envision a team of drones that will essentially meet or visit the whales at the right place, at the right time,” Jadhav said. “So whenever the whales surface, you essentially have a kind of autonomous drone, or autonomous robot, very close to the whale to collect information such as visual information or even acoustic if the drone is equipped with that.”
Outside of Project CETI, organizations could use AVATARS to further protect sperm whales in their natural environments. For example, this information could be used to reroute ships away from sperm whale hot spots, reducing the odds of a ship colliding with a pod of sperm whales.
“The idea is that if we understand more about the wholes, more about the whale communities, more about their social structures, then this will also enable and motivate conservation projects and understanding of marine life and how it needs to be protected,” Gil said.
In addition, the researchers said they could apply these methods to other sea mammals that vocalize.
“Here at Project CETI, we’re concerned about sperm whales, but I think this can be generalized to other marine mammals, because a lot of marine mammals vocalize, including humpback whales, other types of whales, and dolphins,” Bhattacharya said.
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