United States: Stressing rats, New York's effective method to prevent them from reproducing

New York is waging an all-out war against rats, the ubiquitous illegal inhabitants that roam sidewalks, parks, and alleys. Among the methods employed: removing food sources, which is driving down their population.

This food deprivation—through the disposal of waste in the street, the sealing of building access points, and raising awareness among residents—causes physiological stress in rats, which translates into a decrease in their reproduction. "Perhaps this forces them to go further in search of food," but the fact remains that "they simply have fewer young," explains Caroline Bragdon, director of interventions for the city's pest control service. And "less reproduction leads to less rat activity."

“I was even afraid of leaving my son on the floor.”

This phenomenon is being observed in a pilot program in the Harlem neighborhood of northern Manhattan, where the city is testing several combined approaches, including applications to map rodent activity and chemical contraception. "Whatever method you use, it works," notes Jessica Sanchez, a 36-year-old Harlem resident. "Before, when you took out the trash, rats would run right under your feet. I was even afraid to leave my son on the floor. And I'm not even talking about the smell."

Rats, whose diet is similar to that of humans—carbohydrates, fats, and proteins—traditionally find their food in trash left on sidewalks and in overflowing garbage cans. However, this food abundance has favored rapid reproduction and dense populations: a rat can have up to twelve young per litter, with five to seven litters per year, which explains the difficulty in stemming their proliferation. "Reducing their access to food is the most effective measure today," says Caroline Bragdon.

In 2022, the city had already launched its "waste revolution": the end of trash bags on the sidewalk and the installation of plastic dumpsters that now hold 70% of waste. This was after the Covid-19 pandemic, which had seen the number of rats in the city explode. "With these new dumpsters, I no longer feel like I have to run between piles of trash to avoid rats," explains Karen Del Aguila, 50, whom we met in Harlem. "But if it's cleaner, it's maybe just because the mayor is trying to get re-elected (in November, editor's note)."

25% drop

To combat rodents, 70 municipal inspectors have a mobile application that allows them to precisely locate hotspots and direct their interventions. To refine this strategy, the city is also experimenting with devices to study rat feeding behavior. Small boxes containing four different types of food have been installed in certain neighborhoods to observe their preferences. "They are designed to make rats feel safe and comfortable in their eating habits... and we analyze which ones are most likely to be consumed," explains Caroline Bragdon.

The city has increased its budget for rat control, allocating $4.7 million for 2025, up from $3.5 million in 2023. Since the implementation of these combined measures, there has been a significant decline in rat reports, with a 25% decrease in 2024 compared to the previous year, according to official data. Chinatown, in lower Manhattan, is currently the only neighborhood to have successfully controlled its rat population, but the city hopes the trend will spread in the coming months.