Science & Nature
New Year, New-ish Approach to Rat Control in Chicago. But Is the Real Solution Out of the Hands of Streets and San?
(Patty Wetli / WTTW News)
When a snowy owl turned up on Chicago’s lakefront in late November, birders were ecstatic.
They were also worried for the arctic visitor, sharing a common concern on social media: “I hope it doesn’t eat a rat.”
Rats normally make an excellent meal for owls, hawks, eagles and other birds of prey. But too often in cities like Chicago, the rodents are laced with poisons known as anticoagulant rodenticides.
These rodenticides, which interfere with an animal’s ability to cycle Vitamin K and clot blood, are Chicago’s primary weapon in the city’s seemingly neverending war on rats.
“In an ideal world, a rat eats the poison and dies quickly, out of sight,” said Maureen Murray, a wildlife disease ecologist who heads up the Chicago Rat Project at Lincoln Park Zoo’s Urban Wildlife Institute.
In reality, as Murray’s research has shown, the targeted rats are becoming increasingly tolerant of the poison.
“In one study, we tested 101 rats and about three-fourths tested positive for rat poison. These were rats we just trapped in an alley, and they were alive and well,” she said.
Instead, it’s unintended victims like raptors, which eat the poisoned rats — “And we want predators to eat rats,” Murray said — that are dying from the rodenticide.
Flaco the owl — who gained global fame after escaping from a New York City zoo — has been the highest-profile rodenticide casualty to date, but Chicago has experienced tragedies of its own, spurring local wildlife advocates into action.
In spring 2024, residents of Lincoln Park were overjoyed when a pair of great horned owls built a nest in the park and successfully hatched an owlet.
“It was a lovely thing to witness,” said Myriam Renaud.
Then one by one, the owls died: first the adult male, followed by the owlet, and finally the female. Necropsies later confirmed rodenticides as the cause of death.
“Hopefully a new owl doesn’t nest in the park for its safety,” Renaud said.
Renaud was one of several members of the public who attended the Department of Streets and Sanitation’s budget hearing in November, and used the opportunity to speak out in support of a petition calling on Streets and San to cut back on its use of rat poison.
“Our position is that we want to reduce these toxic rodenticides that work their way up the food chain and kill owls and hawks,” said Judy Pollock, president of the Chicago Bird Alliance, which is leading the petition drive.
If not rodenticides, then what?
“There’s not one silver bullet,” Murray said. “Increasing the tools in our toolkit — integrated pest management — would be more effective.”
Streets and Sanitation has signaled it’s inching in that direction.
Dr. Sarah Reich, of Willowbrook Wildlife Center, treats an eagle in 2022 that had been poisoned by rodenticides. (Courtesy of Willowbrook Wildlife Center)
During the budget hearing, Commissioner Cole Stallard touted a plan to reallocate five crews to rodent abatement in 2025.
“I want a crew in every ward, every other day,” Stallard said.
He also said he’d heard people’s complaints about rodenticides loud and clear.
“We’re open for anything to make it better,” Stallard said.
In 2025, the department will begin a trial of carbon dioxide as an alternative solution to rodenticides and is currently preparing a request for proposals from CO2 vendors, according to a spokesperson for Streets and San.
If carbon dioxide sounds familiar, that’s because Chicago tried it once before — in the form of dry ice — during former Mayor Rahm Emanuel’s administration. That trial, which was relatively successful while it lasted, was halted by the Environmental Protection Agency.
In lieu of dry ice, this latest effort will use a gas version of CO2, which is approved by the EPA, the Streets and San spokesperson said.
The gas is pumped into burrows’ entry points, which means you need to locate exits as well, and confirm the rats are present, Murray said.
Currently, the biggest buzz in rat abatement is birth control, which neutralizes the rodent’s superpower: its ability to reproduce exponentially.
“We tried it before and it didn’t work,” Stallard said when questioned about the method.
But according to Murray, the delivery mechanism for rat birth control has changed in the years since Chicago deployed it. What was formerly administered as a liquid, which was logistically challenging control, is now available in a more manageable pellet form.
“I think it would be valuable to study,” she said of rat birth control. “Before we use these products at a larger scale, we have to make sure it doesn’t affect other animals.”
There is one other powerful tool cities have in their rate abatement arsenals, but it’s a sensitive subject to broach.
It’s humans.
“The feeling I get is that this isn’t a rat problem, it’s a people problem,” Murray said.
These unsecured baskets, overflowing with food waste, are rat magnets, according to Streets and Sanitation Commissioner Cole Stallard. (benkrut / iStock)
Humans have a complicated relationship with rats, and as Murray dug deeper into the issue of urban rats, she realized she needed to understand the human angle as well.
Why are people so disproportionately disgusted and freaked out by this one rodent versus almost any other species of wildlife in the city?
“This is such a fascinating question,” she said. “Some has to do with size. People will say, ‘It’s huge, it’s the size of a cat.’ And people bring up (rat) tails a lot.”
People will also point out that rats carry diseases and live in gross environments like sewers, but in surveying people’s responses to rats, Murray also identified psychological components.
Not only do rats cause anxiety and sleeplessness in people, they’re linked to depression.
“People who saw rats daily were five times more likely to have depression,” Murray said, even when accounting for income level, gender and other factors.
In questionnaires, people even went so far as to attribute intentionality to rats, she said, frequently describing them as
“planning” or “scheming.”
But the irony is, the primary reason rats continue to survive and thrive in places like Chicago is because “we provide a sort of endless buffet,” Murray said.
(Patty Wetli / WTTW News)
It’s an issue that came up frequently at the National Urban Rat Summit, which Murray attended this past September.
“There seemed to be a through line that business as usual is not working. There were a lot of interesting presentations ... where we address trash management,” she said.
Trash management — as in reducing waste and/or doing a better job of containing it — would go a long way toward eliminating Chicago’s rat problem, something Streets and San is well aware of.
The department has made an effort to replace damaged garbage bins that were providing access to food scraps, but the city can’t control people’s behavior, Stallard said, and cited a pair of scenarios that work against the city’s attempts to curb Chicago’s rat population.
He pointed to people who leave a restaurant with leftovers and decide on the walk home to toss the food into the nearest sidewalk waste basket — the kind of baskets popular with and maintained by chambers of commerce, neighborhood associations, etc. — the majority of which have openings on the top and bottom. Dog owners will also toss their pet’s waste into these same baskets instead of carrying the baggies home and dumping the waste into a secure bin.
“And that attracts rats. It’s food or it’s feces,” Stallard said.
The commissioner went so far as to single out dog poop as the main food source for rats.
“If I put a pile of dog poop and steak on the sidewalk, people don’t believe it, but the rat will go for the poop,” he said.
“Stop tossing half-eaten food, pick up after dogs, and we’re halfway” to getting rid of rats, Stallard said. “It’s really that simple.”
A citywide anti-littering campaign has been proposed and is pending funding review, the Streets and San spokesperson told WTTW News.
But “give a hoot, don’t pollute” isn’t necessarily what people want to hear when it comes to rats, Murray said.
People will ask, “What do we do?” to get rid of rats, she said, and when the response is “control garbage,” their reaction is “Well, not that. What else?”
“Human behavior is so complex,” she said.
Contact Patty Wetli: @pattywetli | (773) 509-5623 | [email protected]
