Before you drain the swamp, you might need to get rid of some of the rats in the nation’s capitol. Wednesday the Washington Post reported that the number of complaints about rats is up sharply in Washington, DC and rat control experts for the city are recommending a new way of dealing with them:

With complaints to the city’s 311 phone line concerning rats at a four-year high, city officials are turning to dry ice — the frozen form of carbon dioxide — to suffocate rodents. But dry ice will not replace the poison that the District’s rodent control division currently uses, said its program manager Gerard Brown.

“It’s just going to be another tool in our toolbox,” said Brown, who has been killing rats in Washington for 30 years.

His explanation for how dry ice works is concise, and a little dramatic: “The CO2 that emanates from the dry ice suffocates the rats, and their homes become their graves,” he said…

The District’s rat problem is not new, but it has worsened in recent years. The surging rat population is driven by a combination of factors, including Washington’s booming human population, which means more trash, and recent mild winters, which means fewer rats die from frigid temperatures — although city officials are hoping the current cold snap will help reduce the population.

There have been 3,286 rat complaints to the city this fiscal year, up 64 percent from fiscal year 2015, according to data from the health department.

Rats congregate in our largest cities where they can scour the alleys and subway platforms for a free lunch (and dinner). Orkin pest control puts out a list of the U.S. cities with the worst rat problems every year and in the most recent list, Washington actually came in 5th place behind Chicago, New York, Los Angeles and San Francisco. One New Yorker seemed skeptical that any city could have more rats than New York. From the NY Daily News:

“I don’t know about Chicago but I do know New York,” said William Dantzler, 57. “Rats in New York walk on subway platforms with no fear. You stomp your feet in front of them and they look at you like you are invading their space.”

A graduate student at Fordham University recently published a paper which found genetic variations between uptown New York rats and downtown rats. NPR reported last month:

Combs and other researchers spent two years going around the city and trapping rats. After extracting and analyzing their DNA, he determined that the rats that live in uptown, north of 59th Street, are distinct from those living in downtown, south of 14th Street. The Midtown area is more sparsely populated — by rats, anyway — presenting a barrier to genetic mixing…

As for his personal feelings about rats, Combs says the pests are more complex than they seem.

“The more I learn and the more I read about rats, I think the more I’m able to respect them,” he says. “I mean, they’re remarkable creatures — they’re able to change their movement patterns based on the things humans do, so they’re very smart. They’re also very social creatures.”

Yes, the rats are very social. In New York, rats can even become celebrities. This 2015 video of “Pizza Rat” has been viewed over 10 million times: