For the tenth consecutive year, Chicago has earned the unfortunate title of ‘America’s rattiest city,’ according to Orkin Pest Control.
In an effort to shed this unwanted label, city officials are initiating a new program targeting the rat population in the Wicker Park and Bucktown neighborhoods.
Announced late last month, this temporary pilot project is introducing rat birth control into the alleyways behind several key commercial and residential areas within these North Side neighborhoods.
The initiative, sponsored by the Wicker Park Chamber of Commerce and Special Service Area No. 33, aims to reduce the rodent population by focusing on the rats’ most potent ability: reproduction.
Described as a ‘humane control method,’ the birth control product being utilized in the pilot project is called Evolve.
Developed by Arizona-based company SenesTech, Evolve comes in the form of a solid pellet shaped like a sausage.
Its active ingredient, cottonseed oil, impacts fertility in both male and female rats without causing them harm, according to Bryan DiMenna, SenesTech’s vice president of sales.
The product has been recognized as a ‘low-risk pesticide’ by the EPA, indicating that it poses minimal risk to human health and the environment.
“This is a humane control method, not just for the rats but for all the other animals in the ecosystem,” DiMenna emphasized.
He added that it does not damage anything, poison the water supply, and has minimal ecological impact.
This approach starkly contrasts the traditional alternatives, such as rat poison, which is often the first choice for many pest control efforts.
According to Maureen Murray, who leads the Chicago Rat Project at Lincoln Park Zoo, rat poison can lead to a particularly cruel death for any animal that ingests it.
Most common poisons inhibit blood clotting, causing the animal to bleed to death from either internal or external injuries.
“Rat poison is a really big issue for biodiversity,” Murray stated.
She pointed out that rats that have ingested poison can be hunted and consumed by urban wildlife, including owls, hawks, and foxes, affecting the entire ecosystem.
Moreover, Murray has noted a concerning trend—rat poison is becoming less effective as rats have started to avoid it, and some have even developed a resistance to it.
Murray’s study tested 100 healthy rats captured in Chicago’s alleys, finding that 75% had rat poison in their systems.
With a quick reproduction cycle and short lifespans, rats can quickly evolve resistance to poisons, creating an ongoing cycle of inefficiency in traditional rat control methods.
“I wouldn’t tell someone to coexist with rats and just put up with it,” Murray remarked, emphasizing that while rats are intelligent animals, the focus should be on humane methods of control.
Enter the concept of birth control as a more sustainable alternative.
Similar to human contraceptive pills, the effectiveness of the rat birth control relies on the rats continuously consuming the product.
“There’s a cumulative effect with it,” DiMenna explained.
Initial results have shown a 61% decrease in birth rates among treated rats within the first gestation cycle, indicating a significant reduction in litter sizes.
With continued usage, the reduction in birth rates can extend further, ultimately halting their breeding altogether.
Since this form of birth control is temporary, Murray notes that rats will not develop resistance as they would to lethal methods.
“Contraceptives are good because rats have evolved to reproduce quickly,” she stated.
“Slowing down the population makes more sense than trying to kill them all rapidly and is more effective in the long run.”
The birth control pellets have been strategically placed in alleys along North Avenue between Damen and Ashland Avenues; Ashland Avenue between North Avenue and Division Street; Milwaukee Avenue between Division Street and Damen Avenue; and Division Street between Ashland and Damen Avenues.
According to DiMenna, SenesTech is scheduled to return in a couple of weeks to distribute the birth control in residential alleys in the area.
The city previously attempted using an earlier version of SenesTech’s rat birth control, known as ContraPest, but struggled with its liquid administration.
Additionally, the city tried employing dry ice as a means to eliminate rats.
The Chicago Department of Streets and Sanitation has not responded to inquiries regarding the current efforts to manage and lessen the rodent population.
Addressing the rat population is crucial for public health, as a reduced rodent count can lower the risks of diseases such as leptospirosis, a severe bacterial infection spread through rat urine that can endanger both humans and pets.
DiMenna highlighted the shared responsibility of residents in controlling the rat population.
“Just do your part: Pick up after yourself,” he advised.
“Keep your bins closed. Don’t wait till tomorrow. If you see trash, pick it up.”
image source from：https://chicago.suntimes.com/health/2025/04/13/rat-birth-chicago-wicker-park-bucktown-alternative-pest-management
