We humans often watch and wonder at wildlife. But a defence agency’s new initiative turns the tables—it aims to deploy marine animals to keep an eye on human activity.

The agency wants to know if sea life ranging from bioluminescent plankton to goliath grouper can serve as components of underwater surveillance systems capable of detecting the enemy’s oceangoing drones, large nuclear submarines and other underwater vehicles. The research effort is called Persistent Aquatic Living Sensors (PALS).

Many marine animals respond audibly or visibly to sound, optical, electromagnetic and chemical shifts in the water around them. For instance, schools of black sea bass change their behaviour when disturbed by underwater vehicles, and certain microbes react to the magnetic signatures of submarines. Existing surveillance technology can pick up this behaviour but typically has treated it as background noise.

“The PALS program was developed to leverage the great sensitivity that organisms have in the ocean to changes in their environment,” says Lori Adornato, manager of the initiative, which is administered by the federal Defense Advanced Research Projects Agency (DARPA).

Sonar is the conventional approach to underwater surveillance. However, adversaries can detect those pings as well. And sonar sensors are expensive, laborious to instal and prone to being corroded or encrusted with organisms. Some must even remain close to ship or shore to reach power sources. So, the Navy primarily uses underwater surveillance to protect high-value assets, such as ports and aircraft carriers.

Dutch security services expel Russian spies over cyber plot Show all 23 1 /23 Dutch security services expel Russian spies over cyber plot Dutch security services expel Russian spies over cyber plot Russian passports belonging to (top row) Oleg Sotnikov (left), Aleksei Morenets, (bottom row) Evgenii Serebriakov (left) and Alexey Minin, who have been named as the four GRU officers who tried to hack the global chemical weapons watchdog which is investigating the Salisbury nerve agent attack PA Dutch security services expel Russian spies over cyber plot On April 13 the officers parked a car carrying specialist hacking equipment outside the headquarters of the OPCW in The Hague Dutch Ministry of Defence/PA Dutch security services expel Russian spies over cyber plot Specialist equipment intended for the alleged hacking of WiFi networks of the Organisation for the Prohibition of Chemical Weapons (OPCW). Russia's military intelligence service has been accused of trying to hack the global chemical weapons watchdog which is investigating the Salisbury nerve agent attack PA Dutch security services expel Russian spies over cyber plot The Dutch counter-terrorism officers intervened to disrupt the operation and the four GRU officers were ordered to leave the country Dutch Ministry of Defence/PA Dutch security services expel Russian spies over cyber plot Mobile phones and a camera recovered from four GRU officers who were alleged to have hacked the WiFi networks of the Organisation for the Prohibition of Chemical Weapons (OPCW) PA Dutch security services expel Russian spies over cyber plot The four Russians arrived on diplomatic passports Netherlands Defence Ministry Dutch security services expel Russian spies over cyber plot Alexey Minin, who has been named as one of the four GRU officers who tried to hack the global chemical weapons watchdog which is investigating the Salisbury nerve agent attack PA Dutch security services expel Russian spies over cyber plot A car carrying hacking equipment used by GRU officers, travelling on official Russian passports, parked near the headquarters of the OPCW in The Hague Dutch Ministry of Defence/PA Dutch security services expel Russian spies over cyber plot Oleg Sotnikov, who has been named as one of the four GRU officers PA Dutch security services expel Russian spies over cyber plot Hacking equipment belonging to four Russian officers Dutch Ministry of Defence/AP Dutch security services expel Russian spies over cyber plot Evgenii Serebriakov, who has been named as one of the four GRU officers PA Dutch security services expel Russian spies over cyber plot Equipment found in possession of four Russian citizens Reuters Dutch security services expel Russian spies over cyber plot Photos of the Organisation for the Prohibition of Chemical Weapons (OPCW) and its surroundings taken on the 11 April, found on the phone of GRU officer Alexey Minin Dutch Ministry of Defence/PA Dutch security services expel Russian spies over cyber plot Equipment found in possession of four Russian citizens REUTERS Dutch security services expel Russian spies over cyber plot Aleksei Morenets, who has been named as one of the four GRU officers PA Dutch security services expel Russian spies over cyber plot Undated handout photo dated issued by the Dutch Ministry of Defence of a car carrying hacking equipment used by GRU officers, travelling on official Russian passports, parked near the headquarters of the OPCW in The Hague. 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Netherlands Defence Ministry Netherlands Defence Ministry Dutch security services expel Russian spies over cyber plot Dutch security services say they have foiled an attempted cyber attack targeting the international chemical weapons watchdog, during its investigations into the Salisbury attack. Netherlands Defence Ministry Netherlands Defence Ministry Dutch security services expel Russian spies over cyber plot Dutch security services say they have foiled an attempted cyber attack targeting the international chemical weapons watchdog, during its investigations into the Salisbury attack. Netherlands Defence Ministry Netherlands Defence Ministry Dutch security services expel Russian spies over cyber plot Dutch security services say they have foiled an attempted cyber attack targeting the international chemical weapons watchdog, during its investigations into the Salisbury attack. 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In contrast, living organisms are self-powered and can sense visual, magnetic and chemical cues as well as sounds. “This gives you a lot more flexibility in how you would observe things in the ocean,” says Ms Adornato. Plus, these sensors are already “installed” throughout the seas, with each generation naturally replacing the previous one. All these features make ocean life ideal agents for continuous, long-term surveillance. “By taking advantage of organisms, you can then look at persistence and wide-scale coverage as opposed to using one single sensor that does the whole job,” says Ms Adornato.

At least two challenges come with leveraging living organisms for maritime monitoring. First, DARPA will need detectors to pick up on the relevant animal behaviour. Those detectors could face the same problems that trouble conventional sensors. Second, “you have to have some understanding of animal behaviour, and that’s always a huge wild card,” says Kim Martini, a physical oceanographer based in Seattle, who is not part of the initiative.

US military wants to use sea creatures as underwater spies to monitor enemy activity

To see what is possible, DARPA has started to grant a total of $45 million to five research teams, each studying a specific marine organism and its responses to underwater vehicles. Researchers will use some combination of hydrophones, sonar, cameras and other sensors to study and record the organisms’ behaviour. They then will analyse the data to screen out false positives. Finally, the teams will develop technology that can relay signals back to the military.

A group led by Laurent Chérubin, a physical oceanographer at Florida Atlantic University’s Harbor Branch Oceanographic Institute, will use PALS funding to record and analyse the noises made by goliath grouper. These territorial fish, which can grow up to 8.2 feet in length and weigh up to 800 pounds, are known to make distinct low-frequency “booms” when divers approach them. Researchers suspect the boom is a distress call made in response to all kinds of intruders, including underwater drones and submarines.

To test this theory, Mr Chérubin and his colleagues will become well-acquainted with every facet of the species’ behaviour, bringing to light never-seen behaviours, says Mr Chérubin. The work will begin with captive fish before moving on to goliath grouper in natural habitats to see if any behaviours only occur in the wild.

Alison Laferriere, an oceanographic engineer at Raytheon BBN Technologies, will lead a team of biologists focusing on snapping shrimp. Only a few centimetres long, snapping shrimp are one of the loudest marine organisms, producing 200-decibel popping noises that Ms Laferriere likens to the sizzle of frying bacon. The pops travel for long distances, so they could strike enemy vehicles and bounce back to sensors, much like sonar does. “It has the potential to detect even the quietest vehicles that might be there,” says Ms Laferriere.

Ms Laferriere is excited that her PALS project also will contribute to basic research. While listening to the collective shrimp sounds of the ocean, her teams also will monitor habitat health and biodiversity. And they’re breaking new ground; no one has studied how snapping shrimp react to the presence of an underwater vehicle and how that affects the overall soundscape, she says.

Other teams will use cameras and machine learning to look for useful patterns in the responses of bioluminescent organisms to underwater vehicles. All of the researchers are expected to publish their findings, at least the unclassified ones, in the next several years. And when they do, we can listen in too.