When the words "Baltimore" and "rat" appear together, they usually involve a discussion of the fate of The Wire's Wallace or a DVD featuring Carmelo Anthony. However, unlike the alleged turncoats, it seems that actual rodents really do hold down their block. According to a new study in Molecular Ecology by a team of Johns Hopkins scientists, Norwegian rats are as neighborhood-oriented as any of the bipedal residents of Charm City.
The study looked at 277 rats from across Baltimore, and found that the genetic makeup of the city's rat population varied significantly by neighborhood. East Side rats were more closely related to each other than West Side rats, rats from the Ashland neighborhood were closely related to the rats from the neighboring Northeast Market neighborhood than they were to rats from the more distant Winston-Govans neighborhood, and so on.
What makes this study useful is that the researchers found the rats limited their range because of opportunity, not capability. Some individual rats proved they could cross the entire city when spurred by danger, and vacancies left by exterminations were filled by rats from a diverse set of locations.
This means that, in the face of a rat-borne disease outbreak, a program of extermination may actually spread the disease by forcing infected rats into previously unaffected neighborhoods. As a result, public health officials who think they can solve problems with a quick dose of rat poison may need to look for more creative solutions.