Abigail Tucker in Smithsonian Magazine:
Glass has been following the secret lives of wild Norway rats – otherwise known as brown rats, wharf rats, or, most evocatively, sewer rats — for more than two decades now, but Baltimore has been a national hotspot for rat studies for well over half a century. The research push began during World War II, when thousands of troops in the South Pacific came down with the rat-carried tsutsugamushi disease, and the Allies also feared that the Germans and Japanese would release rats to spread the plague. Rats were wreaking havoc on the home front, too, as Christine Keiner notes in her 2005 article in the academic journal Endeavor. Rats can chew through wire and even steel, obliterating infrastructure. Rodent-related damage cost the country an estimated $200 million in 1942 alone. Rat bites were reaching record highs in some areas.
Worst of all, one of the only tried-and-true rat poisons –an extract from the bulb of the Mediterranean red squill plant–was suddenly unavailable, because the Axis powers had blockaded the Mediterranean. Scientists scrambled to find a chemical substitute.
More here.