RatGraph: Visualization of Rat Sightings in NYC

Rats! At times, they seem to be everywhere in New York City, scurrying across the subway tracks or into a dark alley. Statistician Jonathan Auerbach recently estimated that there are about 2 million rats in the city. Rats carry a variety of infectious bacteria, as a recent study by researchers at Columbia University found. In October 2014, the city of New York was rated the 4th rattiest city in the country by Orkin.

The city makes much of its data on reported rat and rodent sightings available to the public. The visualization below uses the data from 311 calls to show how rat sightings vary over time and location.

[+] View the interactive version of this graph

A recent study by Dr. Michael Walsh, Assistant Professor of Epidemiology and Biostatistics in the School of Public Health at SUNY Downstate, combined this rat sighting data with socioeconomic and geographic data and found that "closer proximity to both subway lines and recreational public spaces was associated with a higher concentration of rat sightings, as was a greater presence of older housing, vacant housing units, and low education among the population."

Looking at sightings over time is particularly relevant because NYC is in the process of piloting a new rat control program that uses a chemical, ContraPest® from SenesTech Inc., to reduce rat fertility.

For the scientifically inclined, the main active ingredient in ContraPest is 4-vinylcyclohexene diepoxide (VCD).  This paper provides a good overview of what scientists know about its mechanism of action and effects.  In short, it seems to cause early menopause in female rats.

If the pilot portion of the study being conducted in 2014 is successful and NYC rolls out the program on a wider basis, the number of rat sightings over time should go down.

You can clearly see some seasonal variation in the data.  The most dominant species of rat in NYC, the brown rat (rattus norvegicus), breeds year-around but mates more frequently in the warmer months of the year so this is a likely explanation for the variation.