Rats in New York City are widespread, as they are in many densely populated areas. They are considered a cultural symbol of the city. For a long time, the number of rats in New York City was unknown, and a common urban legend declared there were up to five times as many rats as people. However, a 2023 study estimates that there are approximately 3 million rats in New York, which is close to a third of New York's human population.
The city's rat population is dominated by the brown rat (also known as the Norway rat). The average adult body weight is in males and about in females. The adult rat can squeeze through holes or gaps wide, jump a horizontal distance of up to (or vertically from a flat surface to ), survive a fall from a height of almost , and hold their breath for 3 minutes.
New York City rats carry pathogens that can cause diarrhea, vomiting, and fever in humans – especially in children. The pathogens they carry include bacteria such as Clostridioides difficile (C. diff), Salmonella, E. coli, and Leptospira. Bartonella bacteria cause cat scratch disease, trench fever, and Carrion disease. These bacteria may be spread through contact with rat saliva, urine or feces. Rats can carry disease-causing viruses such as sapoviruses, cardioviruses, kobuviruses, parechoviruses, rotaviruses, hepaciviruses, and Seoul virus. Rats may carry fleas that are vectors of diseases such as bubonic plague, typhus, and spotted fever. In addition, some people have an allergic reaction to the presence of rodent hair, urine or feces.
Description
Species Rarely seen in daylight, rats have been reported in New York City since early colonial days. As recently as 1944, two distinct species were prevalent: the brown rat (Norway rat) and the black rat (ship rat, roof rat). Over the next few decades, the larger and more aggressive brown variety displaced the black rats, typically by attacking and killing them, but also by out-competing them for food and shelter. By 2014, the city's rat population was dominated by the brown rat.
The brown rat is long and weighs . It is brown or gray in color with a lighter-colored belly. It is nocturnal, and sleeps approximately 10 hours a day.Ryan Bradley (April 23, 2015). "The Rat Paths of New York; How the city's animals get where they're going." The New York Times Magazine The black rat is between long (not including the tail) and weighs between . It is usually black to light brown in color with a lighter-colored belly.
Population
Rats are elusive by nature, and public health officials have not developed any reliable way to estimate their numbers. However, a 2014 study by Jonathan Auerbach, which was reported in the Royal Statistical Society's Significance magazine, estimated that there were closer to 2 million rats in the city. In 2023, another study by pest control company MMPC using Auerbach's methodology estimated that the rat population has since increased to nearly 3 million. This is close to a third of New York's human population. It conflicts with the often-repeated statistic that there are more rats than people in the five boroughs of New York City (8.5 million in 2023), with some estimates putting the number of rats far higher at as many as five rats per person (33.6 million).
In 2014, the television channel Animal Planet named New York City the "Worst Rat City in the World". Compared to other cities within the United States, studies indicate New York is particularly well-suited for rats. This conclusion is based on characteristics such as human population patterns, public sanitation practices, climate, housing construction standards and other variables. Experts consider that the actual population of rats varies, depending on climate, sanitation practices, efforts to control the population, and season.
Genetics Studies have repeatedly failed to find restricted gene flow in Manhattan's rats due to the island's buildings. However Combs et al. (2018) presents a more geographically detailed analysis. They find that the island's buildings are restricting gene flow, especially in Midtown. Combs et al. found that there were genetically distinct clusters of rats north of 59th Street (in Upper Manhattan) and south of 14th Street (in Lower Manhattan), although both clusters were likely descended from rats imported from Britain.
Food and shelter Rats only require of food and water a day to live. The rodents primarily find food and shelter at human habitations and therefore interact with humans in various ways. In particular, the city's rats adapt to practices and habits among New Yorkers for disposing of food waste. Curbside overnight garbage disposal from residences, stores, subway and restaurants, as well as littering, contribute to the sustenance of the city's rats. Rats nearly always use the same routes to their food sources. Rat infestations have increased as a result of budget reductions and more wasteful disposal of food.
Rats burrow underground or create nests in suitable soft material, with a small group of rats in each nest. Brown rats in New York City prefer to live at ground level or basement level. They congregate in colonies of 30 to 50 rats. Rats live to from their food source.
Habits Unlike many mammals, the rat's skull is not plated together. This means it can change the shape of its head to squeeze through holes or gaps as small as a quarter (). They are able to leap laterally and can fall five floors without any injuries. An adult rat can tread water for three days. They typically travel tight, well-worn paths. Each litter has up to a dozen pups. Rats can mate at the age of two or three months and then produce a new litter every two months. The rats live for approximately one year, mostly due to predation rather than natural lifespan. They rarely travel more than from where they were born.
Public health The greatest danger posed to humans from rats is the diseases that the latter can transmit. City-dwelling rats carry pathogens that can cause diarrhea and vomiting in humans. Disease-causing bacteria commonly carried by rats include E. coli, Clostridioides difficile (C. diff), and Salmonella. The bacteria can be spread by contact with rat saliva, urine or feces. Viral diseases spread by rats include rat-bite fever and hemorrhagic fevers caused by Seoul hantavirus.
A survey conducted by Columbia University's Mailman School of Public Health in 2014 studied 133 brown rats from residential buildings in Manhattan. The rats carried numerous pathogens that can cause serious illness in humans, including bacteria (Salmonella and E. coli) that cause food poisoning and dermatitis, pathogens that cause fevers (such as Seoul hantavirus and Leptospira), sapoviruses, cardioviruses, kobuviruses, parechoviruses, rotaviruses, Hepacivirus A, and hepaciviruses, including some never before seen in New York. While at least 18 of the viruses found are known to cause disease in humans, it is unclear how infectious the rats are to residents. Peter Daszak, president of EcoHealth Alliance, a nonprofit scientific organization that researches links between human health and wildlife, called the study "shocking and surprising". Given the close quarters shared by rats and New York City residents, he found it to be "a recipe for a public health nightmare".
A 2015 joint study by Columbia University and Cornell University found that the rats are commonly infested with fleas, lice, and mites that carry bacteria that can cause disease in humans, including bubonic plague, typhus, and spotted fever. They found an average of five fleas per rat, a sharp increase from a 1925 study that found one out of five rats had no fleas at all. Bartonella pathogens (which can cause cat scratch disease, trench fever, and Carrion disease) and various viruses were also found in New York City's rats in this study. These results were confirmed by a study published in 2015 in the Journal of Medical Entomology. A higher risk of allergies and asthma is linked to exposure to rodent hair, droppings, and urine, especially in children.
The NYC Health Department recommends that people bitten by a rat seek immediate medical attention, as bacteria from the rat's teeth can cause tetanus as well as rat-bite fever, which can be fatal.
Control
The New York City Department of Health handles enforcement of rat infestation problems in New York City. Local authorities in New York have long recognized that eliminating rats from the city is unrealistic, but have made various efforts to control their prevalence. The approach has traditionally been reactive: after receiving complaints of infestation, officials would commence control efforts at that site by placing rodent poison, traps, or contraceptives.
In recent years, the city adopted a more proactive approach to rodent control known as integrated pest management, which focuses on preventive measures. Such efforts include developing a rodent control map using geotagging to focus countermeasures more systematically, instituting a "Rodent Control Academy" that trains city employees on rat behavior and control, and emphasizing building integrity and garbage disposal. In 2009, the Health Department began offering a half-day course in combating rat infestations. In 2010, the city cut its budget for rodent control programs by $1.5 million to help reduce an overall deficit of $2 billion.
In 2013, it was announced that New York municipal authorities would implement a plan for mass sterilization of the city's rats, using a chemical to neutralize the reproductive systems of female rats. Bait stations loaded with the chemical were to be deployed. The chemical's effects were to gradually shrink the number of pups a female rat can have in a litter, eventually rendering them infertile.
The Upper West Side and the Upper East Side logged the most rat complaints to the Health Department from 2010 to mid-2014. In 2014 the Health Department hired 9 new inspectors to augment its staff of 45. With $611,000 in funding, the new squad was tasked with targeting major infestations in the South Bronx and Manhattan.
Private groups, such as Ryders Alley Trencher-fed Society, conducts rat hunts in New York using dogs.
City-led control efforts
New York City property owners and managing agents are legally responsible for keeping their properties rat-free through maintenance measures and the use of pest control professionals. Conditions both inside and outside of buildings, including on public property, that contribute to or allow the establishment of rat populations constitute violations of Article 151 of the Health Code.
Maintenance measures include proper storage of garbage, removal of water sources, and elimination of environments suitable for nesting. Garbage cans need to be rat-resistant and made out of metal rather than plastic. Because rats easily chew through plastic, the Health Department recommends placing plastic garbage bags inside rat-resistant metal garbage cans. Garbage should be placed out on the street close to the pickup time, rather than the night before. It also becomes important to keep garbage that are in parks inside litter cans, and not feeding birds or any of the surrounding wildlife that could potentially attract them.
New York City publishes a guide for property owners and tenants, entitled Preventing Rats on Your Property: A Guide for Property Owners and Tenants, that discusses how the Health Department inspects for rats, and how to control rats, including looking for evidence, cleaning up, starving them, shutting them out, and wiping them out. The guide covers the use of traps, rat poison, and wire mesh at the base of trees, as well as the new rules for garbage pickup, with landlords bringing out garbage in the morning immediately prior to pickup rather than the night before. Rodent baiting is suggested as an effective approach to wiping out rats.