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How Many Rats Are in NYC?
The population of rats in New York City has always been a topic of interest, especially in the last few years following the COVID pandemic.
It’s impossible to count how many rats are in New York City, but in 2014 a statistician named Jonathan Auerbach estimated that there were as many as 2 million living in the Big Apple.
To reach this number, he used publicly available data on rat sightings reported to 311 between 2010 and 2011 as a proxy for capture-recapture, a sampling method used by ecologists to estimate animal populations in the wild.
More than a decade later, we replicated Auerbach’s methods with the latest data on rat sightings in 2022 and 2023. Our results show that there are now as many as 3 million rats in New York City.
2 Million Rats in 2010
In the field of ecology, capture-recapture (also known as “mark and recapture”) is a method used to estimate large populations of wild animals where it is impractical to count every individual.
- It involves catching a sample group of wild animals (rats, in this case), marking them, and releasing them unharmed.
- After a period of time, once the marked animals have integrated back into the wild population, a second sample group of wild animals are captured.
- Some of the animals captured in the second group are marked, meaning they have been recaptured.
- The proportion of marked to unmarked animals in the second group is assumed to be the same as the proportion of the number of animals captured in the first group to the total population in the area.
In Auerbach’s method, he uses data on reported rat sightings across two discrete sample periods (the first 6 months of 2010 and the first 6 months of 2011) in lieu of physically capturing and recapturing rats:
- City lots with rat sightings in the first sample period (S1) are considered “captured.”
- City lots with rat sightings in both the first and second sample periods (S1 and S2) are considered “recaptured” (R).
- In each neighborhood, rat-inhabited lots are assumed to be equally likely to be reported to 311 and any lot identified during the first sample is equally likely to be identified during the second period.
- The number of rat-inhabited lots in New York City is assumed to be a closed population.
- The total number of rat-inhabited lots (T) within a given area can be estimated using the formula: T = S1 × S2 ÷ R
The total number of rat-inhabited city lots, based on rat sightings from 2010 and 2011, was determined to be 45,000 (±3,000), or 4.75% of all lots in the city.
Assuming that the average rat colony inhabiting an infested lot supports up to 50 rats, Auerbach concluded that there were roughly 2 million rats (±150,000) living in the city in 2010.
Method
In order to understand how New York City’s rat population has changed since Auerbach’s study was published in 2014, we replicated his capture-recapture method using data on rat sightings reported in the first half of 2022 and 2023.
- Data Source: Rat Sightings based on 311 Service Requests from 2010 to Present
- 1st Sample Period (S1): January 1, 2022 – June 30, 2022
- 2nd Sample period (S2): January 1, 2023 – June 30, 2023
City lots with rat sightings in both sample periods were considered “recaptured” (R) and the total number of rat-inhabited lots (T) was estimated using the formula:
T = S1 × S2 ÷ R
In his 2014 study, Auerbach applied his capture-recapture method on a neighborhood level, repeating the process for each of the 195 neighborhoods across the city.
However, in our data there were certain neighborhoods and community districts in which zero lots were “recaptured” (R), making it impossible to use this method to estimate the rat populations in those areas. Due to this limitation, we applied capture-recapture on a borough-by-borough level (Manhattan, Brooklyn, Queens, the Bronx, and Staten Island).
The results are comparable. When we used this approach with Auerbach’s data from 2010 and 2011, we found there were 41,735 (±3,379) rat-inhabited lots — not far off from Auerbach’s original estimate of 45,000 (±3,000).
Using up-to-date data for our sample periods between 2022 and 2023, we found that the number of rat-inhabited lots has since grown to 59,384 (±1,952).
The final step was to calculate the total number of rats. Auerbach assumed that each rat-inhabited lot supports its own, unique colony of approximately 50 rats.
Based on our experience as a pest control company that frequently conducts rat inspections, baiting, and exterminations, that number is likely overestimated. The typical city lot in New York City doesn’t have a lot of space for rodents to form large colonies; on average we find between 1–3 active burrows per infested lot, with around 5–15 rats in a burrow.
3 Million Rats in 2022
According to our statistical analysis, there were 59,384 (±1952) rat-inhabited lots in 2022, which is 7% of all lots in the city. Assuming that each lot supports up to 50 rats, that means New York City now has as many as 3 million rats (±100,000).
That’s an increase of nearly 1 million rats in a decade (up 42% since 2010). Manhattan had the biggest change in rat population (up 66%), followed by Brooklyn (56%) and the Bronx (54%).
| Lots – Rat Sightings (S1) | Lots – Rat Sightings (S2) | “Recaptured” Lots (R) | Total Rat-Infested Lots (T) | Number of Rats | |
| Manhattan | 2,155 | 2,028 | 427 | 10,235 ±394 | 511,750 ±19,700 |
| Brooklyn | 3,434 | 3,397 | 508 | 22,963 ±867 | 1,148,150 ±43,350 |
| Queens | 1,315 | 1,486 | 130 | 15,031 ±1,195 | 751,550 ±59,750 |
| The Bronx | 1,332 | 1,105 | 218 | 6,752 ±375 | 337,600 ±18,750 |
| Staten Island | 259 | 221 | 13 | 4,403 ±1,155 | 220,150 ±57,750 |
| Total | 59,384 ±1,952 | 2,969,200 ±97,600 |
Rats in NYC from 2010 to 2022
Applying the same methodology for each year between 2011 and 2023, we created a timeline chart showing how New York City’s rat population has changed in the last 12 years.
This chart provides some insights into how large-scale events affected the rodent population.
The year with the lowest number of rats in NYC was 2014 (1.8 million), following Hurricane Sandy (Oct 2012) and the subsequent cleanup efforts.
The year with the highest number of rats in NYC was 2021 (3.0 million), during the COVID-19 pandemic as a result of sanitation budget cuts and outdoor dining.
Conclusion
New York City is home to one of the largest populations of brown rats, also known as Norway rats (Rattus norvegicus), in the United States. Norway rats are big, brown, and aggressive compared to other species like roof rats (Rattus rattus), and they are known to infest buildings, damage property, contaminate food, and spread disease.
Unfortunately for New Yorkers, they’re a difficult problem to solve. Rats are intelligent and resilient, enabling them to adapt to various environments. They can even learn to avoid traps and baits. And in a bustling place like New York City, where there’s an abundance of food (think overflowing bins, piles of trash bags on curbs, and outdoor dining establishments) as well as hiding places (subway systems, sewers, and construction zones), it’s no wonder they’re thriving.
Read More: How to Get Rid of Rats Outside: Signs, Tips, and Solutions
About MMPC
MMPC is a top-rated pest control company in New York City, recently named one of America’s Favorite 150 Mom & Pop Shops by Entrepreneur Magazine. We’ve been in business for over 25 years, helping our fellow New Yorkers and local communities solve pest issues like rats, mice, cockroaches, bed bugs, ants, termites, and more.
Contact us today if you have questions about addressing rat issues, or if you need help getting rid of rats on your property:
- Rat inspections and proofing assessments
- Baiting and trapping
- Burrow treatments and removal
- Proofing and exclusion services