Colonies of big-city rat experts work to outsmart rodent community

(This story was updated because an earlier version included an inaccuracy.)

NEW YORK ? Tourists snapped selfies and office workers guzzled coffees inside Manhattan's Bryant Park. But all around their feet ? beneath bushes, over subway grates and between trash cans ? were traps, barriers and birth-control-infused snacks to fend off rats in the heart of the nation's largest city.

Mischief appears to be managed at the tranquil 9.6 acre New York City gathering spot. A mischief is what you call a group of rats. These passersby likely had no clue about the lengths park staff had gone to ward off the city's seemingly unstoppable, half-pound enemy.

Staff were “willing to try anything,” sans rat poison, to rid the iconic park of the vermin, Maddie Baker, operations manager for the nonprofit Bryant Park Corporation, told USA TODAY on a morning stroll on the first Monday of fall.

It's a problem that's plagued mayors and governments for centuries. The park's crew is open to anything that works, Baker said, adding, “We’re always looking to see what people are doing in other cities around the world.”

Wherever humans congregate, rats amass – efficient and unrelenting – in colonies. It's an age-old problem that experts are trying to attack with global strategies. About 25 blocks from Bryant Park, other humans who worry about rats for a living had recently convened on the banks of the Hudson River, where common city rats likely first arrived on ships from the Old World.

The first-ever rat national summit aimed to lay out best practices across North America.

National Urban Rat Summit

In a small conference room in Google's newly renovated Pier 57, officials and experts spent two days discussing formerly popular practices, like extermination, their unintended consequences and why wars against rats won't succeed. Dr. Ashwin Vasan, the city’s health commissioner, told tales of the Black Death during the 14th century speaking to health, sanitation and pest control officials and academics from across the U.S. and Canada.

The problem is not just rats. The Yersinia pestis bacteria from fleas carried by rodents wrought havoc across trade routes and port cities of the Old World, decimating human populations with plague. While plague is no longer an issue, the city still deals with rat-borne illnesses, such as leptospirosis. Sanitation workers picking up garbage on city streets come into contact with rat urine on trash, allowing the bacteria to infect people. The Leptospira bacterium thrives in heat, and a warming planet gives it a home among New York's rats.

“Rat control is no less important" in the 21st century, Vasan said. It's not just about disease prevention. “It’s also about a sense of freedom. Freedom from stress, from fear, and from the feeling that the place you live is in some state of disrepair or disregard.”

Growing cities, growing mischief

Managing a rodent problem is daunting. Doing it right involves tackling competing issues, including, infrastructure, sanitation and the biology of rodents, which are complex, adaptable mammals. Rat reduction requires knowledge about human behavior and psychology.

By 2050, experts say, 70% of people will live in cities. As this happens, urban areas must deal with aging infrastructure with increasing food supply and waste for people, Vasan said. Rats are likely going to try to follow humans into the future.

No American city is perhaps more aware of this dynamic than New York.

“We're big, we're diverse, and we're densely populated, and it's only going to get more like that," Caroline Bragdon, director of the New York City health department’s division overseeing veterinary and pest control services, told USA TODAY during a break from the summit’s first day. “We need to keep pushing ourselves to address the problem, but also do it in a sustainable way.”

Nearly 80 years ago, rats lurked in the city's docks and butcheries, bringing the potential for disease, according to an account in the New Yorker magazine. Then, the most prevalent species was the brown rat or Rattus norvegicus. It is now the only rat in New York City, likely arriving in North America just before the American Revolution. Other port cities still have populations of the smaller black or roof rats, also known as Rattus rattus, which New York hasn’t seen in some time, Bragdon explained.

Rodents prolific in production

For decades, workers have used poison to eradicate rat populations, said Matthew Frye, a pest management specialist at Cornell University. But it can have the opposite effect.

Colonies can die out. But when new rats inevitably reestablish themselves, they face no competition from other colonies, allowing their numbers to flourish.

Frye calls this the “boomerang effect.” A female rat reproduces four to five times per year, with around eight to 12 pups per litter. Like other mammals, rats have “reproductive synchrony,” meaning females in a colony all produce offspring at the same time. “Rodents are incredibly prolific in their production,” Frye explained.

This is especially true if they have plenty of food and water. When that's the case, they'll produce even larger litters. Prolific reproduction often happens near areas where humans live and leave discarded food and waste.

Understanding food sources and “harborage,” or areas where rats like to live, is crucial to addressing the problem. For example, brown rats typically burrow in the ground, near humans. Human choices about food and trash, Frye said, play a part in this.

“It's our behaviors as people that contribute to the rats, but we don't often dedicate enough time to working to change behaviors that will minimize the attractive conditions for rats,” he told USA TODAY. “People first may not understand how their actions contribute to rats."

It's important for communities to consider inequities, he added. They should make plans that take account of the people who don't have resources to deal with rats, or think the issue is beyond their control.

Claudia Riegel, the director of New Orleans Mosquito, Termite and Rodent Control Board, referred to this work as the “wicked problem” of urban rats, in a presentation at the conference. Riegel and others also had a chance to compare notes with an array of rat experts from Seattle, Boston, Washington and British Columbia, Canada.

Unlike New York, New Orleans faces a pernicious rat situation because the city is going after not just brown rats, but also black rats. Each place requires a tailored plan to manage its unique set of rat problems.

“It is impossible to get rid of every rat in a city,” she said. “If you have a structure, a building, it is absolutely possible to eliminate the rodent from that structure. That’s first and foremost – to put it into perspective.”

‘Drug sellers left’ but rats remain in park

Back in Bryant Park, home to the main branch of the New York Public Library and two giant stone lions, tourists and workers huddled under umbrellas and trees as rain intermittently pattered down. The Empire State Building rose just above the nearby buildings, reflecting on a building facing it.

In the 1980s, Bryant Park was known for its drug markets and violent crime. Also, the “smell of urine everywhere, no public restrooms,” said Dan Biederman, the longtime director of the nonprofit Bryant Park, which reopened the space in 1992. “Nobody visited.”

Since then, the space has transformed, with new ownership and donations to cover the cost of keeping it clean. As in the rest of New York City, crime dropped significantly. The flowers are now abundant. There are concerts, exercise classes, cafes and restaurants.

“The drug sellers left, we pushed them out,” Biederman said. “The only thing that was still a problem were rats.”

The park used its funds to take on this nagging problem. When Mayor Eric Adams took office in 2022, he became yet another Big Apple mayor declaring war on the city's rats.

Adams, who now faces federal corruption charges, appointed a rat czar in 2023 to work across multiple agencies, coordinating work by pest control companies and property managers. The city led an initiative to “containerize” trash, since most trash is left on the street, often at night, in plastic bags for trash trucks to collect. Rats are nocturnal, so these are perfect feasting conditions.

The city took rodent fighting to neighborhoods known for high levels of "rat activity." In July, the city formed a “Rat Pack,” volunteers to help in Adams' crusade against rats. The training included a “rat academy” where participants could learn about prevention methods, “rat walks” around the city, and a project, such as cleaning a local park.

Adams' efforts often came with canned jokes at news conferences about Mickey Mouse and proclamations that "rats don't run our city." But he also described it as an issue that haunts the psyche of a New Yorker who, say, wakes up to a rat in her toilet.

Adams jokingly told summit attendees he’d distinguished himself as the New York City mayor who hated rats the most.

Early data on Adams' efforts looks promising. Calls to 311 for rat sightings have declined – a 6.3% drop since the rat czar was appointed and almost a 14% decline in the city’s mitigation zones, the city boasted in a news release announcing the rat summit.

White flags, 'thunder god vine plant'

Around when Adams began his crusade, Baker took a job at Bryant Park. Biederman tapped her to lead pest management. The most interaction she'd had with rodents before was the two pet rats she had as a child.

She began researching the latest strategies. On a walk around the park, Baker pointed out a few examples of what has worked. Following a model in New Zealand, the park uses corrugated plastic, covered in peanut butter, to identify where rats are most active. A white flag rose above ivy, marking where pest control workers had sprayed a rat burrow with carbon monoxide and collapsed the hole. In one quadrant of the park, the team laid out birth control for female rats. Their trial method involved a soft bait of peanut butter, oats and a plant-derived compound found in the thunder god vine plant, which has antifertility properties.

In the beginning, the team found over 70 burrows per week. The park is now down to about five burrows per week. Days, even weeks, pass before the staff sees a rat, though Baker stressed this is "anecdotal." She needed more evidence before she could say they'd gotten that far.

Bryant Park is, in many ways, a model for the city that opened its arms to the first rat summit. However, Bryant Park is managed by a nonprofit. It's unclear whether other less monied parks – let alone smaller cities – can recreate its success. Biederman and Baker say buy-in is crucial.

On the gravel of the park’s pétanque courts, Francois Lelan, a 92-year-old retired bartender from Queens, recalled seeing his last rat in the park over a month ago, near the public restrooms.

For 15 years, Lelan has taught pétanque, a game from his native France, similar to bocce ball.

Monday marked the last week pétanque instructors would be out at the park until April. The game, and the park, helped people relax in the middle of the city, Lelan said.

“Forget about the business,” he said, as he picked up the pétanque balls with a magnet attached to a string. “It’s good.”

At lunch hour, a group of regular players arrived, some wearing suits, one wearing a Seattle Seahawks jersey. Lelan kept watch, studying their game. Nothing to distract or deter them. And no mischief in sight.

This article originally appeared on USA TODAY: Outsmarting New York rats is no longer about extermination