Off the coast of Southern California, amid a literal sea of troubles—warming waters, microplastic pollution, overfishing—is a 96-square-mile conservation success story. Santa Cruz Island once teemed with feral pigs and invasive Argentine ants until the Nature Conservancy unleashed a coordinated campaign of eradication. That’s allowed the adorable island fox to bounce back from the brink of extinction.
The battle was won, but the war wasn’t over, because the Nature Conservancy now has to defend that territory from yet another invader: rats. The scourge of islands everywhere, rats get ashore and breed like crazy, devouring just about everything in their paths—native plant seeds, bird and reptile eggs, local people’s crops. (Urban islands of steel and concrete, especially Manhattan, are of course plagued as well.) Once they’re established, it’s exceedingly difficult to get rid of them. On the Galápagos Island of Seymour Norte, conservationists had to attack them with poison-dropping drones.
So on Santa Cruz Island, the Nature Conservancy has been experimenting with a surveillance system to learn whether rats have landed, using a network of wildlife camera traps and the same AI technique that recognizes human faces in photographs. While scientists have been using various forms of the camera trap for a hundred years, this version automatically detects when a rodent comes into view, then sends an email alert to the conservationists. “You can think about it as a Ring doorbell for rats,” says Nathaniel Rindlaub, a software developer at the Nature Conservancy who’s leading the project.
This innovation was necessitated by Santa Cruz Island itself. Typically, a biologist has to revisit their camera traps every few months or so to grab the memory card and swap the battery. That can mean hiking into a rainforest or, in this case, around a mountainous rock that’s three times the size of Manhattan. By the time you get to your camera, it may have been months since the rat was there—not exactly conducive to a rapid response.
Or, in the meantime, a deer or a bear might knock your camera over. Or a blade of grass whipping back and forth in front of the lens might make it fire off a bunch of pictures super fast. Or the camera might just take thousands of pictures of empty space. “Up to 90 or 95 percent of all your images may just have nothing in there,” says University of Calgary computer scientist Saul Greenberg, who develops image recognition for camera traps but wasn’t involved in this new work. “Forget about recognition. If you can just say that these images are empty, that’s a big win for a lot of people using camera traps.”
Rindlaub’s new system works semiautonomously and in nearly real time to do this kind of weeding out of images. A network of solar-powered cameras are linked by radio. If one detects something, it takes a picture and sends it to the next camera in the chain, which relays it to the next one, and so on until the image reaches a base station connected to the internet. The image is then uploaded to the cloud.
“When images get ingested in the system,” says Rindlaub, “they get piped through a sequence of computer vision models that try to essentially determine what’s in them.” These algorithms are trained to distinguish between native wildlife, like island foxes, and rodents. At the moment, though, it’s only sophisticated enough to look for rodents in general, as it can’t yet tell the difference between the native deer mouse and an invasive rat. Each time it sees something vaguely rodential, it fires off an email to Rindlaub and his colleagues, whose human eyes are more than capable of telling the difference. So far: no rats detected on Santa Cruz Island.
But this newfangled surveillance is still needed, because the island allows visitors by boat. All it takes is a pair of stowaway rats to make landfall, and the Nature Conservancy has a serious problem on its hands.
Islands are difficult to defend against invasive species. Native animals often are not used to such predators, and don’t know how to defend themselves because they haven’t coevolved with their opponents. As a result, “We’re losing more species on islands than anywhere else in the world,” says David Will, head of innovation at the nonprofit group Island Conservation, which undertakes eradication efforts and is working with the Nature Conservancy to trial the new camera system. Rats, along with pigs and cats, are leading causes of those extinctions. “If we remove those invasive species, then we can see these remarkable recoveries on islands. It’s one of the most impactful things that we can do to protect biodiversity,” Will continues.
Oddly enough, what makes islands so fragile also makes them easier to manage. On the mainland, if you want to protect a chunk of land from an invasive species, you have to constantly beat back repeated invasions around the edges, since there’s nothing stopping the animals from coming in from the outside. Island ecosystems are easier to quarantine because they’re surrounded by water.
Still, that turf has to be constantly monitored, especially if people are still boating in. “Having a real-time surveillance system in place would be a really remarkable approach for a lot of these islands,” says Will—even ones that haven’t yet been invaded, as a preventative measure. The technology would in theory be cheaper and less laborious than having people do surveillance the old way, and the algorithms could be trained to detect other invasive species, like feral cats.
Conservationists are exploring an additional layer of security in the form of testing “environmental DNA,” also known as eDNA. This means taking samples of soil or water to search for the DNA signatures—left in feces or urine—of rodents or other invasive species.
Scientists can also deploy chew blocks, or little pieces of plastic smeared with peanut butter—if they’ve got rat-teeth-sized holes in them, that means trouble. “You can imagine real-time camera trap systems, chew blocks, and eDNA as a series of different techniques to help keep an eye on biosecurity, or help confirm whether an eradication has been successful,” says Will.
That’d be a cohesive defense system, but it’s not fully automated: The camera traps can detect rodents on their own, but it’s still up to a human to confirm what they’re seeing. And with eDNA and chew blocks, humans are involved every step of the way. These technologies are tools, says Will, not standalone invasive-species-busting solutions. “It’s been a hope that machine learning would solve everyone’s problems and you never have to look at photos again,” he says. “The reality is—especially in a biosecurity context, where you want to have 99 percent probability that you’ve detected a rat—there’s always going to be people in the loop.”
