KELLY MCEVERS, HOST:
In New York City there's an old thing about whether you are an uptown person or a downtown person. Turns out this also applies to rats. Matthew Combs is a graduate student at Fordham University who studies rats. He has just published a paper about the genetics of brown rats in New York, and he's with us now. Welcome.
MATTHEW COMBS: Thank you.
MCEVERS: So when we think about people researching rats, I think a lot of us imagine, you know, these little fluffy lab rats. But you study New York City rats, which I would imagine is a very different type of rat. Can you explain why you're interested in them?
COMBS: Sure. So despite the fact that rats live right in our cities and under our feet, under our noses, there's actually quite little knowledge about how they behave in cities, how they move around. They are a serious public health threat. They carry several zoonotic diseases that we are worried about. So the more we know about how they move, how these colonies interact, the better we can create management strategies to stop them.
MCEVERS: So tell us about this latest study. How did you determine that there are uptown rats and downtown rats?
COMBS: Sure. So we spent about two years collecting rats all over the city, trapping them ourselves. Once we did that, we would take a sample back to the lab and extract DNA. And from that DNA we looked at thousands of little genetic changes to see who was more related to whom. And we realized that there were two pretty unique clusters of rats, those uptown rats and downtown rats. And we were able to analyze that with a few separate analyses.
MCEVERS: So what do we know now that you've done your study?
COMBS: Sure. So we know that related rats, rats in the same colony, tend to stay within about 200 to 400 meters of each other even over multiple generations. So that tells us that most rats actually stay right very close to where they were born. But we do know that a small number, maybe 5 percent or so, actually leave their colony and jump maybe across the block, across the park, or sometimes even further up to a couple kilometers. And those are the rats, those dispersing rats, that can actually move genetic information and move even their pathogens and lead to that spread of disease and that gene flow that we detected.
MCEVERS: Oh, OK. So it sounds like the fact that rats are staying within these small areas, like, a couple - it's basically like a couple big New York City blocks - is a good thing.
COMBS: Yeah, it is a good thing. It's not a good thing if your neighbor has rats because it means that you have rats as well. That's not quite in line with the way that we deal with rats. Most often in the city if a person who owns a property has rats they receive a fine. They're told to deal with it. But it turns out that it's really a problem more on a community scale, more on the scale of an entire block. So we're hoping that with this information we can change how we deal with rats and maybe expand the scope at which we are trying to control them.
MCEVERS: OK. Have your thoughts about rats changed since you did this research?
COMBS: Yeah. The more I learn and the more I read about rats, I think the more I'm able to respect them. 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. So things like that have shocked me.
MCEVERS: So you have more respect for them?
COMBS: Absolutely.
MCEVERS: Fordham University graduate student Matthew Combs, thank you so much.
COMBS: Absolutely.
(SOUNDBITE OF LAPTOP INSTRUMENTAL'S "UPTOWN GIRL")
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