Ratropolis

On Sunday May 11, 1940, months after Nazi Germany defeated Poland and the day after its armies invaded France, Belgium, and the Netherlands, Richmond’s newly elected mayor Gordon Ambler mobilized citizens for a local attack he called “a blitzkrieg.”

“An army of … fighters will set forth to tackle the enemies in their stronghold,” the Richmond Times-Dispatch wrote, previewing the mayor’s battle plans. “This is the last day the [enemy in Richmond] can frolic around and have a good time without a care in the world.”

The mayor’s enemy: Rats. They were everywhere. They scavenged in dumps, vacant lots, and alleys, feasting on untidy scraps left behind by markets, restaurants, and homes. Health officials estimated that there were at least 400,000 of them, more than twice the human population of the city recorded by the federal census that year. When Ambler declared a “war on rats,” he pledged that their days in Richmond were numbered.

Only they weren’t. Like every other urban rat eradication effort ever launched in the history of cities anywhere, the rats held on to their turf. Descendants of the ones on whom Mayor Ambler declared war are almost certainly among the ones that frolic in Richmond today.

One of the biggest issues at the root of the rat problem is that we don’t really understand them. We don’t have a good grasp of how they respond to our efforts to get rid them or fully understand the scope of their threat to us as disease carriers. Our ignorance keeps sending us back to the same frustrated lamentation: Can we please just go our separate ways?

Urban ecologist and biology professor Jonathan Richardson has been trying to tease out this knowledge from the dark corners of downtown Richmond. Alongside him, he often has one or more of his undergraduate research students — Nick Gonzales, ’23, Katelyn Wing, ’22, and Ryan Szykowny, ’22. On a typical night, they converge near an unkempt alley around sunset, put on reflective safety vests and camp headlamps, and begin what Richardson calls his “rat safaris.” They go in search of rat habitats in the middle of the city, places where they lurk near food sources but can quickly hide at the first sign of trouble. This often means poorly lit alleys with uneven pavement framed by half-used garages, basements, and back entrances — and garbage, the more the better. They place live-capture traps baited with bacon grease, peanut butter, and oats, then retrieve them in the morning.

What first stands out on a rat safari is visual: the graffiti on dirty walls and the trash on the ground. With a little time, cracks in the concrete and spaces under doorways start to morph into portals for the darting rats that catch an attentive eye. The next thing that hits is the smell, particularly after standing in one spot for more than a few seconds. The summer heat radiating from the pavement amplifies the intense odors of a grease trap or half-eaten meals bused from tables and dropped in the dumpsters hours earlier. Then come the sounds. Rats vocalize with something between a screech and a chirp, and once the ears start to pick it up, it is a chorus of call and response.

Just as the senses slowly adjust under a night sky in a meadow, they sharpen here. Motion becomes more and more apparent in dark corners. A hole at the base of a trash bin might reveal a nose or a bit of tail. A rat might scurry halfway down the alley and duck down a stairwell within inches of someone’s foot. Another might run along the edge of a wall, dash under a dumpster, and disappear up through an opening they’ve chewed in the middle of the metal bottom.

Often, a rat safari plays out right behind the kind of restaurant that sells $13 burgers with a $2 up charge for a side of sweet potato fries. The research team regularly encounters couples out for the night as they head to their nearby parked cars in shimmering skirts and nice slacks, oblivious to almost everything in the ecosystem around them until Richardson inevitably chats them up. Police officers sometimes drop by to ask why they’re there. Students sometimes ask themselves the same question.

“We talk about it with each other,” Wing, one of the student researchers, says. “We’re frequently like, ‘How did we end up here?’ I realize that not a lot of people like talking about rats, but once they’re impacted by rats, they’re super-passionate about getting rid of them. I’m living off campus this summer, and there was a rat that came out of our trash at the back of our apartment. My friends I’m living with were like, ‘No one else is taking out trash except you. You know the rats.’”

Richardson and his students go on these safaris to answer some basic ecological questions: What are the rats doing? How are they interacting with their environment? How closely are they related to nearby populations, and what diseases do they carry?

“You could ask the same questions for any organism, like a grizzly bear in the pristine areas of Montana,” Richardson says.

Ecologists and other biologists have long trained their eyes on just this type of majestic subject. Central American butterflies, Australia’s Great Barrier Reef, big mammals roaming the savannas of East Africa or the plains of western North America — these were the places scientists went to understand the natural world. The study of flora and fauna in the middle of dense human settlements — called urban ecology — didn’t begin to take serious root until the 1970s. As a result, scientists often know comparatively less about the ecology of the environments in which most of us sleep, work, and play.

“Somewhere between 50 and 55% of humanity lives in cities at this point,” Richardson says. “Our cities are setting up natural selection in a way that we just don’t understand because it’s all new and hasn’t been the focus of research.”

Rats have been living alongside humans for centuries. Ecologists use the term “commensality” to describe the relationship. Its Latin roots — com (with) and mensa (table) — translate to something like “eating together.” However, to be commensal is not necessarily to be convivial, as many a tense Thanksgiving dinner proves. We do not have to like each other to find ourselves sharing the same table. Still, the contours of our relationship with rats are largely a mystery.

Rats have long proven significant and fascinating to us, both environmentally and culturally, for reasons good and bad. They are widely blamed for transporting the fleas that brought the bubonic plague into the ports of Europe, North Africa, and the Middle East during the 14th century. Rats are the first sign of trouble in Albert Camus’s The Plague and a tool of torture in George Orwell’s 1984. Fascist regimes of the mid-20th century slurred their foes by calling them rats, and a mob informer is a worthless traitor who rats out his friends. We respond to bad news by evoking them as an epithet — “Rats!” — and we hate, hate, hate the rat race.

But there’s also a flip side to our relationship. A Belgian nongovernmental organization has trained rats to sniff for land mines, and rats beat humans into space (admittedly, with human help). The Russians launched two of them into low orbit in 1960, and a French one named Hector launched on a rocket in 1961, two months before Yuri Gagarin’s historic flight. They can be vehicles for narrative empathy — take Templeton of Charlotte’s Web and the frustrated would-be chef Remy of Ratatouille. Rizzo the Rat is Gonzo’s voice of reason on The Muppet Show, and pop culture has given us both pizza rat and Chuck E. Cheese. Bob Geldof, who organized the charity concert Live Aid in 1985, gained fame as the frontman for the Boomtown Rats. For a time, some of America’s smoothest crooners called themselves the Rat Pack.

When we think of a literal rat, we tend to think of Rattus norvegicus, often called the Norway rat or brown rat. Thought to have originated in China or Mongolia, the species has now spread to every continent except Antarctica. About 100 years ago, scientists began breeding R. norvegicus. That albino strain of the species is the lineage used in labs across the world today, including at Richmond, where behavioral neuroscientist Kelly Lambert has made headlines worldwide by teaching rats with names like Sophia and Aletheia to drive little cars, part of a study designed to shed light on issues such as emotional resilience.

The rats that Richardson and his students are trapping in Richmond’s urban alleys are nothing like Sophia and Aletheia. “These rats will bite your face off,” he says. One of the things that trapping allows Richardson to do is study the rats’ DNA to better understand population dispersal. In a study in Salvador, Brazil, he worked with local authorities to study the effects of a city eradication program designed to drive rats out of slum areas, where they pose health risks to residents.

“We know we get short-term benefits from lethally removing these guys,” Richardson says. “But ecologically, we know we’re removing a lot of the competition for all the individuals that we don’t pull out of that population.”

That’s what happened in Salvador and likely in Richmond in the 1940s and is the all-too-predictable result wherever eradication is attempted — the rat population falls but then rises again. Richardson studied the DNA of the Salvador rats before and after the campaign to better understand why the bounce-back happens. He determined that Salvador’s population rebound was driven primarily by the descendants of the survivors rather than rats moving in from nearby neighborhoods.

“Almost never have there been systematic efforts to understand what is the best long-term solution to bring these populations down,” he says. “We show no indication that efforts are succeeding for any more than a few months. Coming up with long-term solutions is the only way we’re going to figure this out. Understanding the ecological part of this as it relates to public health — for me, that’s where I want to be.”

The public health implications are significant. Rats carry zoonotic diseases, the kind that jump from animals to humans. Some of the most common concerns related to rats include bacteria that cause leptospirosis and cat scratch fever and the parasite Toxoplasma gondii, the worry of cat owners when they empty their litter boxes. Zoonotic disease risk from rats appears to be more pervasive in disadvantaged areas, though Richardson and other researchers are still documenting this.

“Where you have more rats, you also tend to get more clinical infections that rise to the status of being reported by medical authority groups, which usually means you go to the hospital or some medical clinic,” Richardson says. “There’s also a psychological aspect of this. If you’re surrounded by rats, you don’t feel comfortable. You may always wince when you open the cabinets.” Richardson’s collaborators in Vancouver, British Columbia, captured the unease in the title of a 2019 study: “‘They’re Always There’: Resident Experiences of Living with Rats in a Disadvantaged Neighborhood.”

Additional risks abound. In rural areas, rats can decimate crop fields. In the tightly packed favelas of Salvador, people might not have the ability to store food in ways that prevent rats from contaminating it. Rats can destroy infrastructure as they chew through wires and asphalt. In a New York City park that Richardson was tracking, rats burrowed so extensively under the bricks and concrete that they caused a playground to collapse, falling 2 to 3 feet below the surface level around it.

That intersection where ecology, public health, and social equity meet is at the heart of Richardson’s current research project in Richmond. The goal of his study in alleys on dark nights is to learn the environmental and social factors that influence rat populations and the health risks they pose. The research, supported by a grant from the Jeffress Memorial Trust, is the first to look at Richmond’s rats since the days of Mayor Ambler’s blitzkrieg.

It’s a graduate-level project for his undergraduate students, all of whom are working on related projects and often helping each other. Richardson keeps the mood light in the streets and back in the lab at UR’s Gottwald Center. This summer, near the fridge where he stores DNA vials and other sundries, including a frozen beaver tail, he put up a magnetic dart board.

“I feel super lucky to be in this lab,” Wing said. “Something I’ve really appreciated about doing research here is that you’re working directly with your professor as your mentor. We’re working on our own independent projects. Hopefully we’ll be able to come out with a paper before we graduate and be the first author on these papers, which is a huge accomplishment. Dr. Richardson has been guiding us directly. I honestly think that he focuses more on our projects than he does his own.”

Wing has been engaged in a yearlong meta-analysis, combining data from more than 230 research papers into one gigantic database to reveal socioeconomic and environmental factors that correlate with the prevalence of rat-related zoonotic diseases in locations across the world. Szykowny, who is from Connecticut, spent part of his time in the lab this summer examining 60,000 photos from motion-activated trail cameras set up near a construction site in Somerville, Massachusetts, as part of an effort to understand the effects of demolition on wild rat activity. (One of his terms of art is “rats per unit of time.”) Gonzales, a Virginian, does double duty in Lambert’s lab, teaching rats to drive. All are planning to go to medical school.

“What I’ve learned is that you fail constantly throughout the scientific process,” Wing says. “You can’t go into the day expecting everything to go right. Something’s going to go wrong, and you just have to work through it and figure it out.”

Szykowny says the research is a welcome change from classroom labs. “I felt a lot of times like a chef following a recipe,” he says. “At the end of the day, if I succeeded it was because I could follow instructions that were given to us. I wanted to do research because I knew there’d be opportunities for long-term projects. It’s a space to fail and learn, and you actually have the chance to fix your mistake and find a solution.”

Richardson’s wild rats also provide useful data for his faculty colleague Lambert, of rat-driving fame. Her research already compares the stress levels of rats living in different types of laboratory environments. Data from the wild rats lets her and collaborator Krista Stenger, associate professor of biology, directly compare the neuroanatomy and physiological status of wild rats with the rats who live in the comparatively low-stress lab environments. The team can also evaluate just how far these lab strains have diverged from their wild ancestors.

Through systematic trapping, data gathering, and analysis over the next year, Richardson will provide the first characterization of Richmond’s rat population and the pathogens and parasites it carries. Back in the lab, his team uses tails, feces, spleens, and other biomaterial to develop a host of data about each trapped rat. They run it through various pieces of lab equipment to extract and analyze DNA — useful lab skills for the students to develop.

Because they know exactly where they trapped each one, they are also using sophisticated mapping software to correlate the biological data with multiple types of GIS data, looking systematically for patterns. The data might show, for example, that environmental features such as temperature, topography, or distance to water affect rat population. Richardson is also working with UR’s Digital Scholarship Lab to investigate possible socioeconomic connections such as whether the rat population, or parasite and pathogen prevalence related to them, correlate with data such as median household income and other social equity measures.

Data such as this is important for constructing habitat suitability models — statistical models that tell us where in the city the rats like to live and where they are most likely to carry which pathogens and parasites. This data will help the researchers develop models to predict the likelihood of rats occurring in areas they do not sample. From all of that should emerge the first picture of the social variables that explain inequities in vulnerability to rat-borne diseases.

“It wasn’t until recently that we started incorporating socioeconomic variables into urban ecological data,” Richardson said. “I would say that in the last year or two, it’s been a much bigger part of the conversation in urban ecology.”

The overarching goal, from a scientific perspective, is replicability, which has often been a challenge for ecologists. If scientists see something interesting in one petri dish, that’s great, but it doesn’t start to become noteworthy until they see it in 20. The variables of the natural world are harder to control for. That’s one reason Richardson has led research in multiple cities and why he has collaborators around the world. Cities are replicable units, he says. No two are identical, but they share enough commonalities that replication can draw out general principles.

“It’s great that we have biologists out there trying to track down answers in Richmond, New York, Salvador, and New Orleans, but most of the cities don’t have anybody tracking this stuff,” he says. “We need some general insights that are useful for the cities that don’t have the resources or expertise to do these studies. The replication part of this is what’s going to solve the problem globally.”