Rat-ical Solutions to Chicago’s Rodent Problem

Rats! Whether categorized as rodents, wildlife, vermin or pests, they have a profound impact on human populations in big cities — affecting wide-ranging aspects of residents’ lives from food to psychology to safety. In Chicago, which has been ranked the rattiest city in the United States for eight years by pest control company Orkin, experts are finding new solutions to educate about and hopefully eradicate the invasive species known as the sewer rat. Cover graphic by Emily Fischer for Midstory.

“There are lots of animals that can use our backyards that can potentially have diseases … But with rats, it seems to really get in people’s psyche.” 

Dr. Maureen Murray, a wildlife disease ecologist at the Urban Wildlife Institute housed in the Lincoln Park Zoo, has heard her fair share of rodent horror stories. 

“People mention not being able to sleep because there are rats in their house, or they’ll tell me a story about seeing a rat in their yard from years ago,” she said.

But ratty tales are more important than you might think: Murray said that in order to understand the size and demographics of a rat population, scientists rely on people’s self-reported rat interactions. 

In Chicago, Murray said no one really knows how many rats are living in the city. But in general, rats live within a 150-yard radius of their burrows, especially because cities offer robust food sources, according to Murray. 

At the same time, rat complaints are rising in Chicago suburbs. Rebecca Fyffe of Landmark Pest Management said the company has recently received its first rat calls to places like Hinsdale and Lake Forest, where they’ve never serviced. Rat call frequency has also greatly increased in Evanston, Skokie and Des Plaines, according to Fyffe. 

“Do we think that they expanded their territories 150 yards at a time, or do we think that they walk along train tracks? I don’t know. It really seemed like the first calls that we were getting in certain ‘burbs were where train tracks extended out to those towns,” Fyffe said. 

The other factor to consider in suburban rat evolution is the pandemic. According to Murray, rats could have been pressured to seek food elsewhere when restaurants in the city started to close. Rats were then reported a lot more often in residential areas, especially as people were staying home and producing a lot of trash. 

“With rats, since they’re so intimately tied to how humans manage their garbage, how they manage their homes, how they manage transportation even — there are so many overlapping systems of government logistics and household management — …it’s really tricky to point to a single smoking gun,” Murray said.

A reason for rat proliferation overall could be milder winters, as Murray said that overwinter mortality and lower reproduction during cold months causes any animal population to slow in growth. Moreover, rats are territorial creatures and male rats will defend territory when resources are scarce in harsher weather conditions. Thus, Murray said, there are fewer “loser males” in mild winters because it’s not as competitive an environment. 

Wildlife epidemiology is an important factor in Chicago’s rat population, too. Fyffe said diseases in wildlife operate on a pendulum, which swings back and forth with time and is geographically specific. For instance, 65% of Baltimore rats were found to have antibodies for leptospirosis, while Fyffe’s team found only 5% of Chicago rats do. In that context, Chicago rats are healthier than other areas in the United States. 

And while no one loves a rat infestation, ingrained fears about the creatures do contain some misinformation. Murray said that nearly 80% of people surveyed believed rats carry rabies, which, scientifically, is a rare occurrence. On the flip side, only 30% of people correctly identified leptospirosis and hantavirus as common in rats. Murray said people are much more likely to encounter rat waste infected with one of these diseases than be bitten by a rabid rat, for instance. And humans aren’t the only ones at risk; according to her team’s surveys, dogs in Chicago are increasingly contracting fatal leptospirosis — which can be transmitted through rat waste in areas with standing water. 

Image courtesy of Maureen Murray. 

But the spread of disease doesn’t stop with our pets. Fyffe founded Landmark Pest Management after her aunt and young cousin contracted meningitis and encephalitis from a pigeon colony in Chicago’s Cabrini Green neighborhood, resulting in her cousin’s passing. This experience inspired Fyffe to combine social justice, public health and pest control to protect Chicago area residents from similar situations.

“People who are living in certain conditions [could] have health issues or be deprived of the ability to have a normal life because of potentially the way we manage urban pest issues,” Fyffe said. 

Fyffe works to empower community members to trap and dispose of rats on their own and enhance their quality of life without having to rely on the city or expensive private services, she said. For example, Fyffe’s team spent a few weeks at an urban garden with a rat problem, training garden leadership on the trapping process so that they could advocate for it with other garden members. 

“My team actually won the diversity award from the Daily Herald for the most diverse team because we work in every neighborhood in Chicago. We very actively recruit from those neighborhoods because we just feel like nothing shows more respect to a neighborhood than letting them be serviced by someone who’s from that neighborhood,” Fyffe said. 

As Fyffe’s mission grew, she eventually contacted Dr. Murray about studying deceased trapped rats from Landmark, and the Chicago Rat Project was born. 

“We segued sort of from just trapping rats in alleys with this pest control company to using surveys and interviews to understand people’s experiences with rats,” Murray said. “How often are people seeing rats? How often are people exposed to rat waste in their house? What impacts does that have on their mental health? What barriers are people experiencing when it comes to controlling the rats in their house? And what are their preferences and perceptions of different ways to control rats?” 

Although rats are animals, Chicago deals with them under the streets and sanitation department rather than animal control, which typically deals with species like opossums, skunks, raccoons, squirrels and snakes. 

Murray said that as an invasive species, Norway rats — the rat species infesting cities like Chicago — are different from other wildlife because they depend on people for sustenance, and they exist separately from the natural ecosystem. In 2021, a survey that Murray put out included the question “Are rats wildlife?” which did not elicit a clear collective answer. 

“It really depends who you talk to whether or not rats are even considered wildlife,” Murray said. 

Image courtesy of Zeynel Cebeci via Wikimedia Commons. 

Rat-mitigation strategies — like those that use rodenticide — also affect other animals, according to Murray. Of 97 deceased skunks, raccoons and opossums that Murray’s team sampled, 100% of adults were exposed to some type of rat poison. Animals either eat poisoned rats or eat the teal-colored bait itself, as Murray’s team found teal-colored contents in their stomachs. 

If you live in Chicago or another large city, Murray said the best bet for avoiding rats is properly storing your trash so rats don’t depend on it as a food source. 

“Stash your trash — just make sure that you’re sealing up all the garbage, you’re closing your lid, you’re calling the city to get your garbage can replaced if there’s a hole chewed in it,” Murray said.

Meanwhile, Fyffe said that if you suspect a rat has been inside your home, it is most important to sanitize any food contact surfaces. Certain cleaning solutions, as outlined by the CDC, target certain pathogens like E. coli and Salmonella that rats carry. Removing shoes before entering the home also prevents the spread of rat waste you may have encountered outside.


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