There Are 3 Million Rats in NYC, a 50% Increase Since 2010

MMPC conducted a statistical analysis on city-wide rat sightings using a method proposed by Jonathan Auerbach in 2014. Based on our findings, there are now as many as 3 million rats in New York City.

How Many Rats Are in NYC?

The population of rats in New York City has always been a topic of interest, especially in the years following the COVID pandemic. 

While it’s impractical to count how many rats are in New York City, a statistician named Jonathan Auerbach estimated in 2014 that there were as many as 2 million living in the Big Apple.¹ To reach this conclusion, he used publicly available data on rat sightings reported to 311 between 2010 and 2011 to estimate the number of rat-infested lots in the city.

More than a decade later, we replicated Auerbach’s methodology using data from recent years to find out how the rat population has changed. Our results show that there are now as many as 3 million rats in New York City.

Background – 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 when counting individuals is not feasible:

• 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 already marked, meaning they were previously captured in the first group and have now 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 his 2014 study, Auerbach used data from 311 calls about 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. Furthermore, 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.

Methods – Estimating NYC’s Rat Population in 2023

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 2023 and 2024. 

• Data Source: Rat Sightings based on 311 Service Requests from 2010 to Present²
• 1st Sample Period (S₁): January 1, 2023 – June 30, 2023
• 2nd Sample period (S₂): January 1, 2024 – June 30, 2024

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 during the first half of 2023 and 2024, we found that the number of rat-inhabited lots has since grown to 62,969 (±2,240).

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 performs rat control services throughout the city, that number is likely overestimated. The typical city lot doesn’t have a lot of space for rodents to form large colonies; on average we see between 1–3 active burrows per infested lot, with approximately 5–15 rats per burrow.

Results – 3 Million Rats in 2023

According to our statistical analysis, there were 62,969 (±2,240) rat-inhabited lots in 2023, which is 7% of all lots in the city. Assuming each lot supports up to 50 rats, that means there are 3 million rats in New York City.

That’s an increase of 1 million rats (51%) since 2010. Queens had the biggest change in rat population (up 59%), followed by Manhattan (up 58%) and Brooklyn (up 55%). 

Applying the same methodology for each year between 2011 and 2023, we can visualize how New York City’s rat population has changed in the last 13 years. This may provide some insights into how large-scale events affected the rodent population, such as Hurricane Sandy (Oct 2012) and the COVID-19 pandemic (2020-2021).

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 NYC, 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.

If you need help keeping your property free from rats, MMPC is here to help! We are a top-rated pest control company in New York City with over 30 years of experience with rat treatment and exclusion services.

About the Author

Timothy Wong is the technical director of MMPC, an eco-friendly pest control company in Long Island City. He has over 20 years of pest control experience, holds professional licenses in NY, NJ, PA, and MA, and has published papers on bed bugs and pest control methods.

References

1. Jonathan Auerbach, Does New York City Really have as Many Rats as People?, Significance, Volume 11, Issue 4, October 2014, Pages 22–27, https://doi.org/10.1111/j.1740-9713.2014.00764.x ↩︎
2. 311 Service Requests from 2010 to Present | NYC Open Data. (n.d.). NYC Open Data. https://nycopendata.socrata.com/Social-Services/311-Service-Requests-from-2010-to-Present/erm2-nwe9/data ↩︎