clock menu more-arrow no yes mobile

Filed under:

On the front lines of humanity’s high-tech, global war on rats

Last May, a member of Alberta’s rat patrol paid a visit to a farm on the outskirts of Sibbald, a small town near the Saskatchewan border. He found holes bored into the foundation of a grain silo and feces littering the trash pit: telltale signs of a rat infestation, probably 100 strong. He scattered aquamarine pellets of poison, then returned with seven pest control officers, including Phil Merrill, head of the province’s rat patrol. Using a crane, they hoisted the granary off its foundation, watching for anything scurrying out, one officer standing ready with a shotgun. All the rats were dead. The patrol stomped on the burrows, then burned the silo for good measure. It was a bit of a disappointment, Merrill said. A few years earlier, they’d gunned down 157 rats at a single farm.

Josh Dzieza an investigations editor covering tech, business, and climate change. Since joining The Verge in 2014, he’s won a Loeb Award for feature writing, among others.

Grate Hero Rats

Enemy at the Grates

On the front lines of humanity’s high-tech, global war on rats

By Josh Dzieza

Last May, a member of Alberta’s rat patrol paid a visit to a farm on the outskirts of Sibbald, a small town near the Saskatchewan border. He found holes bored into the foundation of a grain silo and feces littering the trash pit: telltale signs of a rat infestation, probably 100 strong. He scattered aquamarine pellets of poison, then returned with seven pest control officers, including Phil Merrill, head of the province’s rat patrol. Using a crane, they hoisted the granary off its foundation, watching for anything scurrying out, one officer standing ready with a shotgun. All the rats were dead. The patrol stomped on the burrows, then burned the silo for good measure. It was a bit of a disappointment, Merrill said. A few years earlier, they’d gunned down 157 rats at a single farm.

Merrill was swigging chocolate milk and recounting stories of past infestations as we drove toward the control zone, a sparsely populated buffer between Alberta, the largest inhabited rat-free region on Earth, and the rest of the infested planet. There was the rat in an Air Canada cockpit (chased down the tarmac, killed) and the infestation at the dump (poisoned, monitored with night-vision cameras to be sure). Keeping the province rat-free requires constant vigilance, and every spring and fall, Merrill and his team patrol the zone.

All members of the genus Rattus are banned from the province, but Alberta is especially alert for one species: the brown rat, also known as the wharf rat, sewer rat, and Norway rat. That last one is a bit of a misnomer: the species traces its origins to northern China and reached Europe only in the 18th century, where it scurried aboard ships and made landfall in North America around the time of the American Revolution. Fast, strong, and highly adaptable, it’s now present just about anywhere humans live or visit.

Burning down the farm

A structure in Alberta suspected of rat infestation and subsequently burned down. Image courtesy of Phil Merrill

Alberta had the good luck of being one of the last places rats invaded, and in 1950, the government decided to keep them out rather than try to control them once they gained a foothold. The first and most important step was to teach Albertans — some of whom had never seen rats before — to fear and hate them. Preserved rat corpses were exhibited at schools and fairs, and the government printed World War II-style posters depicting a province besieged by rodent hordes. The message was clear: if the rats were to be kept out, all citizens had to do their part — fortifying their farms, reporting incursions, and if need be, taking up arms.

The campaign has been largely successful, and half a century on, Albertans remain vigilant. Merrill’s rat patrol has a hotline, 310-RATS, where people can report possible sightings. The hotline gets hundreds of calls a year, mostly false alarms — misidentified muskrats or pocket gophers. When Albertans do spot a rat, they often act quickly, beating it to death with bats or shovels before calling it in. They even report their neighbors for keeping pet rats, or fancy rats, as exterminators call them. Rats are rats, and Alberta’s government gives them no quarter. Sometimes the owners have their rats flown out of the province, but generally, Merrill said, "We take care of them."

Alberta’s landscape makes eradication feasible. It’s sparsely populated, and its sprawling farms and small towns provide few structures where rats can shelter from the harsh winters. The 250,000-square-mile province is protected by the Rocky Mountains in the west, frigid forests to the north, and badlands to the south. Accordingly, the government concentrates its efforts on a 400-mile-long strip on the eastern border with Saskatchewan.

As the nine members of the patrol travel through the control zone, they check every building that might harbor a rat. They examine foundations for signs of gnawing, ask farmers if they’ve seen anything suspicious, and hand out buckets of poison pellets. Merrill, an energetic and affable 64-year-old who’s worked pest control since 1971, says that the key to catching a rat is to think like a rat: you want a granary, preferably an old wooden one; you want bales of barley or something with a bit of protein to snack on; and you want water. Each time Merrill clears a site, he marks it on a GPS map with a skull and crossbones.

We pulled up to a farmhouse, and Merrill knocked on the door. "Rat patrol here, come to see if you’re harboring any rats," he called out. A gangly, weathered man in his 60s invited Merrill in, pulled out a chair, and the two swapped local rat gossip.

They discussed a dilapidated grain house just over the border in Saskatchewan. As a rule, rats stick close to home, rarely traveling more than a few hundred feet from their nest, but when things get too crowded, some venture out, running through the surrounding fields; most die, but a few find a new building and start to breed. Merrill reckoned there were hundreds of rats in the grain house, and the colony was sending rats out in a 5-mile radius. With the cooperation of the other province’s pest control officer, he wanted to poison it, maybe raze it completely. "We’ve got to fight them over there so we don’t have to fight them over here," he told me.

The control zone is a buffer for Alberta, but now Merrill wanted a buffer for the buffer. How far can his rat campaign go, I asked him. Forever, he said. "I know Alberta can do it. Saskatchewan has seen the vision and is two-thirds rat free already. Montana has very few rats; they could be rat free. Vancouver, New York, port cities would be more difficult, but eventually I think we can win there, too. I think the world — we’re winning. We’re going to win."

Rat Poster resized

"Rats are Coming!" c. 1950s, a poster commissioned by the Government of Alberta. Source: Provincial Archives of Alberta

For thousands of years, people have devised all manner of traps to crush, poison, smother, and electrocute rats. We bred terriers to kill them, then used ferrets to flush them out of their holes. Bounties were offered, and parties were organized to club, shoot, and stab them. People tried feeding them wet plaster, hoping it’d harden and kill them (it didn’t). We tied tiny bells to them, hoping they’d scare other rats away (it didn’t). People sniped them from trees and gassed them in ships. In the 1960s, The New York Daily News declared "all-out war on rats" and armed teens with poison: "1,000 teeners will spearhead assault on rats," read the declaration. "War is on!"

So far, the war has been as futile as it’s been bloody. Rats thrive in the new ecosystems humans have made: they lurk in city infrastructure, eating our waste; they infiltrate farms, eating stores of food; and they hitchhike on global trade, devouring birds, turtles, and anything else they come across. Far from beating them back, we’ve helped rats spread to every continent except Antarctica.

The rat’s future looks bright. Trade is accelerating, and cities are expanding as their infrastructure decays. But in a few places, people are bringing new tactics and technology to the war on rats. Scientists, city planners, exterminators, engineers, pilots, and ordinary citizens are all enlisted in these new campaigns, which offer hope of finally pushing back the rat, at least for a while.

If there’s a constant in the history of rat control, it’s the sense that there must be a better way. An early 20th century Department of Agriculture report is florid in its despair: "For centuries the animal has been banned, and human ingenuity has been taxed to the utmost to suppress it," wrote David E. Lantz. "Everywhere the history of the contest is the same. Though thousands are killed, the relief is only temporary, and other thousands soon replace the slain. Therefore, if conducted along the old lines, the war promises to be never-ending."

Chemicals developed in the middle of the 20th century raised hopes that perhaps technology could vanquish the rat. But rats are cautious — neophobic, is the technical term. They’re so wary of new things in their environment that experienced exterminators leave traps unset for days, letting rats become accustomed to eating from them. Modern anticoagulant poison is designed to be slow-acting, bursting the rodent’s capillaries days after ingestion, so that other rats won’t associate the bait with death.

The problem is that rats breed too quickly for poison to make much difference. The Norway rat has a three-week gestation period and can produce five litters a year, each with four to eight offspring. In as few as three months, those rats can produce litters of their own. In theory, a single pair is capable of giving rise to thousands of progeny in under a year.

So, we kill them as fast as we can. We kill rats because they eat our food and defecate in whatever they don’t eat. They once caused famines, though in modern agriculture they’ve been reduced to a nuisance — the FDA publishes limits of acceptable "rodent filth" per gram.

We kill rats because they’re reservoirs of disease, including plague, which wiped out 60 percent of Europe’s population in the 14th century and for which we’ve never forgiven them. They swarm with other diseases as well: a recent study of rats caught in New York City found pathogens proven to cause salmonella, E. coli, hantavirus, and Leptospira, as well as 18 previously unknown viruses.

We kill rats because they destroy the things we build: they gnaw on wires, starting fires, and gas lines, causing explosions. Their burrows collapse streets and sidewalks. Today, some of the most aggressive rat control projects are carried out by ecologists, trying to kill rats before rats kill native fauna. Every era hates rats in its own way.

We hate rats because they thrive in the places we try to forget: sewers, empty lots, derelict buildings, mountainous landfills. "Rats live in man’s parallel universe, surviving on the effluvia of human society," writes Robert Sullivan in his book Rats. When they scurry onto the subway platform or pop out of our toilets — an urban legend that’s all too true — it’s like a furry little return of the repressed. They’re ambassadors of entropy, appearing in huge numbers during floods, wars, economic decline, or other periods of disorder. All of that is captured in a pervasive feeling: rats are gross.

South Georgia Helicopter

Extermination efforts in South Georgia. Photography by Tony Martin

In late March, on a glacier-riven sliver of land 1,000 miles off the coast of Antarctica, a team of conservationists completed the largest rat eradication ever attempted. Over the course of four years, and at a cost of $12 million, they used helicopters to bombard South Georgia Island with almost 400 tons of poison bait. It’s the most ambitious attempt yet to turn back the rats, and the mission’s measure for success is unforgiving: if a single rat is left alive, they’ve failed.

When project leader Dr. Tony Martin first visited South Georgia 20 years ago, the impact of the rats was stark. Neighboring rat-free islands were brimming with birds and lush with plants fertilized by their droppings. South Georgia itself, however, was barren as a desert. "I thought at that time if I could ever get rid of the rats I’d die a happy man," Martin said, at home in Cambridge after a long journey from the South Atlantic.

Before humans set foot on its shores, South Georgia was a refuge for penguins, albatrosses, and other seabirds. But then came the sealers, and they brought the rats, which devoured the birds: eating eggs, chicks, and even fully grown birds, Martin said, grabbing their necks and devouring their brains while still alive. It's estimated that 90 percent of the island's seabirds have been wiped out by rats.

South Georgia’s story has played out on islands around the world. A disproportionate amount of the world’s biodiversity lives on islands, where species often evolved in isolation from mammalian predators. But when rats arrived, these ecological niches became smorgasbords. Burrowing, ground-nesting, and flightless birds were eaten quickly. Baby tortoises were gnawed to death. Rats are responsible for about half of all bird and reptile extinctions on islands, according to Gregg Howald of the group Island Conservation.

"I have enormous regard for rats," Martin said. "I get no pleasure out of killing them. But the way I look at it, and I recognize this is a very imperialistic view, is that something is going to die here whether we do something or not, and the choice therefore is not whether to kill or not, it’s whether we kill rats, which were introduced by man, or allow the rats your forebears put in place to eradicate the native population. Because I have the power, the resources, to kill rats, and hereby save species from going extinct, I choose to use that power."

Aerial rat eradication was pioneered in the 1990s in New Zealand, where, as Elizabeth Kolbert wrote last year, defending native birds has become an issue of nationalism. They are, after all, Kiwis. Conservationists loaded poison into modified fertilizer buckets and used them to disperse bait evenly over entire islands. Some birds would succumb to the poison, but it was worth it: researchers found that if they killed every last rat, native bird populations quickly rebounded beyond pre-eradication levels. GPS changed the game, according to Keith Springer, a New Zealand conservation officer who worked on the South Georgia mission. It let them overlay islands with a close-knit grid that helicopter pilots could trace, ensuring that no spot is missed.

Other groups copied the strategy. In 2007, Ecuador began clearing the Galapagos Islands of rats, which threatened to wipe out the islands' tortoises. The eradication program was a success: last year, for the first time in over a century, tortoises were born in the wild on Pinzon Island and survived. In the Aleutians, the US Fish and Wildlife Service killed every rat on Rat Island, where a shipwreck had deposited them in the 1780s. Puffins and cormorants quickly returned, and the island was renamed Hawadax.

At 100 miles long, South Georgia is the most ambitious island eradication effort attempted yet. The team divided the island into three sections, each separated by a glacier, and used helicopters to fly along the GPS grid they’d drawn, flinging poison nuggets from a bucket 150 feet above the ground. It’s been several years since the first two sections were poisoned, and the team has seen no sign of rat survivors.

On March 23rd, after weeks of storm delays, Martin watched a helicopter fly out to strafe the island with the final load of poison bait. "It’s strange," he said. "I’ve thought about this moment for the last six years — it consumed my life. I imagined we’d be exultant when the last load went out, but we were completely flat. We just stood there thinking, now what?"

He’s hoping for more eradication projects, bigger projects. He’d like his team to travel the world, "a kind of baiting flying circus," he said. When I spoke with him, he was optimistic, having just read a paper in the journal Biological Conservation imagining what the next generation of rodent eradication might look like.

The paper outlines an arsenal of possible technologies. There are automatic traps like the Spitfire, which sprays sticky poison onto rats when they pass through a tube, killing them when they lick it off, and the A24, which uses a CO2-fired piston to smash their skulls. Species-specific poisons could be dropped by drones day and night. Maybe the most ambitious method involves the release of transgenic rats, engineered so that their progeny would be entirely male. If their offspring were capable of spreading the transgene, it could theoretically drive rats to near extirpation without the use of poison. Their incredible fecundity would finally be thwarted, and after several generations, a horde of bachelor rats would fight amongst themselves, dwindle, and disappear.

Rat hero image

I recently met up with rodent expert Bobby Corrigan in Lower Manhattan. It was one of the year’s first warm evenings, and the faint, sweet whiff of putrefying garbage filled the air. Corrigan stood in the middle of the street, watching rats dart out of a storm drain and into trash bags piled on the curb.

"You can read a city," Corrigan said, pointing to dark streaks leading out of the grate. They were marks left by grease from the rats' fur, soaked and rubbed onto cement from commutes back and forth along the same routes for months or years. Exterminators call them rat runways, and you can see them on the walls and curbs throughout the city.

Last week, New York announced an ambitious new strategy in its war against the city’s intractable rat population. The health department is hiring 50 people, effectively doubling the staff who deals with rats. They’ll survey neighborhoods to find "rat reservoirs," the hidden places where rats have been able to grow to huge numbers, causing problems in neighborhoods no matter what residents or exterminators do. "It’s not just looking for signs of rats; it’s following rats and figuring out where they’re going," said Dan Kass, Deputy Commissioner for Environmental Health.

Inspectors will seal up cracks in sidewalks and foundations. Exterminators will collapse burrows and poison intensively for months. Sewers will be flushed regularly, and health educators will work with neighborhoods to design better trash management programs, possibly including things like vacuum-sealed trash compactors. Population biologists will monitor progress in the area, moving on only when there’s been a sustained decline in rats. In the program’s pilot, areas near the targeted reservoirs saw an 80–90 percent drop in rat sightings, according to the department.

Corrigan helped design New York City’s pilot rat program — he’s a sort of global adviser to cities trying to cope with rats. When he’s cited, which is often, it’s with the epithet "renowned rodentologist," and he has the fastidious intensity of someone who spends a lot of time studying animals that thrive on sloppiness. He’s been called to battle rodents in Warsaw, Sao Paolo, Tokyo, and 46 states, but New York, he says, is "ratropolis."


Bobby Corrigan inspecting New York City rat burrows.

Norway rats came to New York in the 18th century and quickly swarmed the city’s docks, stables, slaughterhouses, and refuse-strewn streets. As the city’s population grew, so did the rats’. Here they have vast temperature-regulated burrows in the sewers and subways, while the city’s aging housing stock furnishes them with basements, walls, and facades to nest in. The parks supply them with plenty of soil to burrow in and a steady supply of pizza crusts and chicken bones.

"New York City is ratropolis because it’s trashopolis," Corrigan said. The city produces 14 million tons of garbage each year, and much of it sits out in bags on curbs or in alleyways each night, conveniently close to the catchment basins where rats dwell. And that’s just the trash that gets properly thrown away, not tossed on the sidewalk. "I call it food shrapnel," Corrigan said, gesturing to the litter underneath benches in the park. "Who’s going to set off the next grenade?"

"New York City is ratropolis because it’s trashopolis."

Corrigan clipped his flashlights to his belt, slipped on a fluorescent orange vest, and put on a green hardhat. We proceeded down Worth Street, stopping occasionally so he could hop up and down in flowerbeds to cave in some burrows, trying to scare out the rats. "This burrow is probably too big," he said after his foot plunged through the soil up to his ankle. "It’s probably decades old, and they just heard me and retreated to the north quarter." The burrows were everywhere, running under seemingly solid sidewalks, streets, and parks. "You can see statues in parks that are starting to list because of all the burrows under them," Corrigan said. "They’re disassembling the city."

Corrigan doesn’t hate rats — quite the opposite. "I absolutely respect them, like them, admire them," he said. He calls them one of the most finely designed mammals nature ever created.

They’re fast, able to run 7 feet per second, he said, running down a list of the rat’s strengths. They can swim and climb and squeeze through holes as small as a quarter. Their jaws are strong, exerting up to 6,000 pounds per square inch, and the enamel on their teeth is harder than iron. They’re clever, "diabolically clever," Corrigan said. They breed quickly and can cram into tiny spaces. "If you want to kill the rats in this park, you’d have to kill 96 percent or you’d be exactly where you started a year later," he said. And like us, they’re omnivorous, adaptable, generalists.

"This is an absolutely incredible animal," Corrigan told me. He’s seen rats in remote corners of Central Park, burrowing to eat earthworms, living like moles; rats stalking pigeons, dragging them into their burrows; rats raiding the Jamaica Bay Wildlife Refuge, eating terrapin eggs. A colleague of his reported seeing rats swimming in the Hudson, eating floating garbage and fish.

Rat Running

"The problem is they want our space as much as we do," Corrigan said. They dash along subway platforms and ride in train cars. Unsatisfied with leftovers, they venture into restaurants. They moved into the brand new Conde Nast offices, even before the editors arrived. Sometimes a rat exploring a sewer follows a smaller tunnel up and out and into the toilet bowl of terrified apartment residents. New York’s 311 program received 24,511 complaints about rats last year, up from 22,365 the year before. That represents about 40 percent of the complaints directed to the Department of Health and Mental Hygiene.

No one knows how many rats live in New York. The one rat per person statistic, often cited, is bogus. A grad student recently attempted a calculation based off 311 complaints and came up with 2 million, but even that’s a total ballpark.

The sun had set by the time we reached Chinatown’s Columbus Park, a hotspot cited by Kass in his announcement of the reservoir program. At the park’s entrance, someone had jammed a shard of concrete into a rat burrow, "a sign of human frustration," Corrigan said. Six or seven rats gathered around a styrofoam container, taking turns sticking their snouts into a hole and tossing it around, trying to get at whatever leftovers were inside. Tired of waiting, a smaller rat dashed across the sidewalk, scaled the fence, and leapt into an open garbage can.

The rats of New York City are too entrenched to be eradicated: the density of the city makes a thorough patrol like Alberta’s unfeasible, and their proximity to us makes the sort of poison campaign used in South Georgia impossible: it would kill them, but it could kill us, too, and more would arrive to take their place.

Instead, Corrigan said, we have to manage their population by targeting the source of their sustenance, and often that means changing human behavior. That’s a major part of the reservoir strategy: taking community leaders around to look at hotspots, working with them to rat-proof buildings, cutting down on littering, and improving waste management services. It’s a massive civic undertaking, both at the neighborhood and policy levels. Poison should be the last thing you go for, Corrigan said. Rats are a symptom of larger issues.

The rats aren’t going away, Corrigan said, as we watched them standing on their burrows, watching us. "We’re going to share the city."

Red Silo

Phil Merrill inspecting a grain silo in Alberta. Photography by Josh Dzieza

As with all great pests, we like to joke that rats will outlast us. After all, they survived nuclear tests on the Marshall Islands. If anything, they're even better positioned to thrive in today’s slower, environmental apocalyptic scenarios. In a world where ecosystems are being upended, cities are growing, infrastructure is aging, and waste is increasing, the rat has all the traits necessary for success. In the Darwinian sense, the rat is just as fit for the world we’ve built as we are.

Today’s rat campaigns are attempts to rein in the rare species that excels under our new rules. With enough effort, money, and technology, we may be able to control their numbers. But the thing about rats is that we always win the battles, but they tend to win the war. Undoing the work of a couple stowaway rats takes millions of dollars and months of helicopter bombardment, but it would be for naught if one pregnant rat hops off a visiting yacht. In cities, just keeping them to manageable numbers takes the work of public officials, exterminators, trash collectors, and scientists, as well as the attention of every citizen. And in Alberta, holding them at bay takes province-wide vigilance and regular border patrols.

We always win the battles, but rats tend to win the war

After making the rounds in the control zone, Merrill drove over the border to Saskatchewan. We drove past the burnt-out hole where an infested granary used to be, over close-cropped hills of wheat and barley, and toward a decrepit grain storage facility that sits in the bottom of a muddy valley. "This is where they’re coming from," he said as we approached. "Jeepers creepers, look at those holes."

The base of the building was riddled with burrows and surrounded by drifts of rat feces — some of it bright blue, a sign of a past poisoning attempt, clearly futile. Merrill became dismayed as he surveyed the scene, climbing up to peek in a window, kneeling to look at the foundation. He decided the building had to come down. Otherwise the rats will keep coming, and eventually some will get through the zone.

Afterward, at the regional pest control headquarters, he checked his email and found some photos of dead rodents caught near Edmonton. He’d gotten the call earlier but figured someone had misidentified a gopher. They hadn’t. They were rats.

Over the phone, he told the Edmonton pest control officer where to get poison and traps. Conferring with other officers, he talked about sending someone to investigate how the rats got in. "Never a dull moment," he said, ruefully, testing the trigger on a shiny CO2-powered trap. Maps of the zone lined the walls of the office. A taxidermied rat sat on the shelf, baring its teeth.

* *

Photography by Andrew White

Edited by Michael Zelenko