SCOTT SIMON, HOST:
Now, if you can stand it, a story about rats, cats and birds. "Hickory Dickory Dock." First, the rats - Washington, D.C., like most major cities, has a major rat problem. No, this is not some sly reference to Congress. And last year, complaints to the city about rodents were up 65 percent. Now, some residents have turned to an ancient method of rat control, but as Jacob Fenston from member station WAMU tells us, even that's not without controversy.
JENN WATTS: So I'm going to lift it up.
JACOB FENSTON, BYLINE: Jenn Watts is lifting up a patio paver in the small backyard behind her row house.
WATTS: So you can see, like, this is essentially what - they've dug down and made these tunnels. And you can actually see, like, pieces of trash and like glass.
FENSTON: Beneath the patio is a maze of rat nests and tunnels running from yard to yard up and down the entire block.
WATTS: The rats don't respond to poison. They don't respond to traps. And now, we're all convinced that nature is the only solution.
FENSTON: By nature, she means rats' natural predator.
WATTS: Which is cats. And now we're all about the cats (laughter).
FENSTON: On the morning I met Watts, she was getting a delivery of two feral cats from a local animal shelter.
ERIN ROBINSON: All right. They don't look as freaked out as I thought they they might. That's great.
WATTS: Hello.
ROBINSON: They're just coming right out.
FENSTON: It's a new program called Blue Collar Cats. Unadoptable feral cats get a home rather than being euthanized, and the homeowner or business gets free pest control.
WATTS: I bet you they can already smell the rats. Welcome to your kingdom, ladies.
FENSTON: The history of cats, rodents and humans dates back more than 9,000 years. When our ancestors first started farming and storing grain, that attracted rodents, which in turn attracted wild cats, which humans eventually adopted as pets. So it just seems natural to use cats as pest control, right? Well, maybe not.
PETE MARRA: Cats are probably the second most devastating non-native invasive mammal on the planet.
FENSTON: This is Pete Marra, director of the Smithsonian Migratory Bird Center. Ironically, he says cats are second only to rats. And maintaining feral cat colonies is a threat to local birds. Marra co-authored a study a few years ago that found cats kill as many as 4 billion native birds each year in the U.S. Cat advocates scoff at the study, saying the number is so high it's not credible. But Marra says not only are cats bad for the ecosystem, they don't really hunt rats.
MARRA: They're not a desired prey species.
FENSTON: But cats are famous rat killers, right? There's even a cartoon about it. Well, here's another expert to burst that bubble.
GREG GLASS: Well, you remember in "Tom And Jerry," that was a mouse. That wasn't a rat.
FENSTON: Greg Glass should know. He spent 30 years at Johns Hopkins University studying rats. He found that contrary to what you might expect, feral cats had no effect on the overall rat population of alleys in Baltimore.
GLASS: I think to some extent, it reflects our own kind of biological ignorance in that yeah, cats are really quite good predators of small rodents.
FENSTON: Huge alley rats? Not so much. But programs using feral cats to combat rats are popping up all over the country. And maybe that's because for some people, it's not actually really about the rats. Here's Aaron Robinson, who runs the Blue Collar Cats program in D.C.
ROBINSON: I mean, I'm not really advertising and talking about rodent control or rodent abatement because that's not my job. My job is to find a good home, a good outcome for these cats.
WATTS: Good morning.
FENSTON: Hi, Jenn, how are you?
I checked in again with Jenn Watts a few weeks after her cats were delivered. So far, they haven't won the war against rats here, but there have been some victories.
WATTS: Actually, I felt like was one of the biggest accomplishments of my life (laughter), was I came out into the back deck, and there was half of a rat's carcass sitting on my deck as a present from the cats. It was amazing (laughter).
FENSTON: If the cats aren't keeping all the rats away, she's convinced it's because there aren't enough of them. She's working on her neighbors to adopt more alley cats. For NPR News, I'm Jacob Fenston in Washington. Transcript provided by NPR, Copyright NPR.