Rats. In major cities you see them everywhere. Behind dumpsters. Scurrying along subway platforms. But they usually only come out at night. When you see them active during the day, that’s when you know your city is infested.

As residents start clamoring for pest control, cities often mount expensive eradication campaigns – without consulting scientists to figure out the best long-term strategies, explains Jonathan Richardson, an urban ecologist who studies rats at the University of Richmond. He fears a worst-case scenario in which the poisons they use only kill off the sick and weak rats – leaving the strongest to thrive and multiply.

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Cities around the world appear to be harboring increasing numbers of rats. robert cicchetti/Shutterstock.com

Super rats or sickly rodents? Our war against urban rats could be leading to swift evolutionary changes

Jonathan Richardson, University of Richmond

Cities often embark upon drastic and expensive eradication campaigns designed to rapidly rid the city of pests like rats. But are the surviving rats stronger or weaker than before?

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