Times-Union readers want to know:
I saw a Washington Post story online that says that exterminators estimate that the rat population in any urban area in the U.S. is one rat per person. Is that true?
People who keep rats as pets appreciate their intelligence, cleanliness and quiet nature. But many only see them as disease-carrying, dirty animals — which they can be. And because they hide in dark places — and Hollywood has promulgated the rat pack belief — there’s a fear that thousands of them are lurking just waiting to pounce. So it’s not hard to imagine that the rat population is as large as the human population.
But, according to Robert Sullivan, the author of “Rats,” this statistic is based upon a nearly century-old misunderstanding and greatly exaggerates the true number of rats to be found in a typical city, according to Snopes.com.
The “one rat per person” claim originates from a study of rats conducted in England by W.R. Boelter and published in 1909 under the title “The Rat Problem,” Snopes.com reports.
Boelter surveyed the English countryside (but not villages, towns, or cities), Snopes.com found, and estimated that England had one rat per acre of cultivated land. Since England had 40 million acres of cultivated land at the time, Boelter said the country’s rat population was 40 million. Coincidently at the time, England also had a human population of 40 million, so it followed that the country had one rat per person.
The 1:1 ratio between people and rats, however, was only relevant to where and when Boelter did his study, not a figure that could be applied everywhere, as Snopes.com points out.
In 1949, Dave Davis, a rodent control expert, analyzed New York’s rat population and called the one-rat-per-human statistic “absurd,” Snopes.com reports. He had just completed a precise calculation of the rat population of Baltimore by trapping rats, counting burrows and measuring such things as rat droppings.
He turned to New York, where he started his survey on six blocks in East Harlem. An experienced trapper trapped rats in apartments for a week. Davis determined there was an average of three rats per apartment in Harlem buildings, mostly living in the kitchen and bathroom but traveling through many floors, Snopes.com stated.
He also found that more people thought they had rats than actually had them — about 10 percent more. When he finished his work and added up his findings, he didn’t find the 1:1 ratio. Even the New York waterfront, which always had been associated with rats, was less infested than assumed. Davis put the rat population of New York at the time at one rat for every 26 people, or 250,000 rats.
Still, Sullivan’s book says that male and female rats may mate 20 times a day. A female can produce up to 12 litters of 20 rats a year: One pair of rats has the potential for 15,000 descendants in a year.
That’s a lot of rats.
So, Sullivan noted, it wouldn’t be unusual for people to continue to use the 1:1 figure; indeed, it has been used in newspaper stories in the Chicago Tribune and the Toronto Star in 1991; the New York Times in 1996; and The Washington Post in 2002 (the article cited in the viral email).
E. Randy Dupree, who oversees the New York City Health Department’s Bureau of Pest Control, was quoted in the Times story as saying that “there are about 8 million rats living in the five boroughs. That’s about one rat per person.”
Pamela Miller, a deputy New York city health commissioner, was quoted in several newspapers as saying, “There’s no official rat census. The estimates are anywhere from one rat per person to 10 rats per person. The truth is probably somewhere in the middle.”
That’s how the information gets passed around — and these are legitimate people speaking in respected publications.
So if the scrabbling sounds and squeaks you hear coming from your attic or from the roof makes you err on the side of more rats, you’re not alone. Could it be like the old saying, “For every cockroach you see, there are 10 more you don’t see”?
Carole Fader: (904) 359-4635
Fact Check: 1 rat per person? Is that for real? – Florida Times-Union
rats – Google News