Throughout much of the 20th century, Baltimore was the epicenter of rat research, with the “golden age” of that science led by Johns Hopkins University ecologists David E. Davis and John B. Calhoun into the 1950s. Their extensive field and lab studies “remain the best source of information available for many aspects of rat biology,” wrote the authors of a new paper published in September’s rat-themed issue of the prestigious academic journal, Science. But all that actually began here even before them.
Rats first made their way up the Chesapeake Bay and Patapsco River around the turn of the 19th century. On land, the rodents multiplied between the city’s wharves, warehouses, and narrow rowhomes, inspiring mom-and-pop exterminators to take out advertisements in the local newspapers as early as 1846. But no real dent would be made for another century, when, in 1942, Hopkins School of Medicine psychobiologist Curt P. Richter, later known as the “Pied Piper of Baltimore,” accidentally discovered a lethal compound that lab rats couldn’t taste.
And it was perfect timing. In the midst of World War II, Allied powers feared the Axis might use rodents as biological weapons. The day’s most popular rodenticide then hailed from the war-torn Mediterranean, and in their scramble to find a substitute, the U.S. government employed Richter to test his new concoction in the back alleys of East Baltimore, then heavily populated by low-income Black residents.
The results were “quite encouraging,” wrote Richter in his 1968 memoir, Experiences of a Reluctant Rat-Catcher. Soon enough, he was hired by city hall. And over the next few years, his Rodent Control Project—the earliest predecessor of today’s Rat Rubout—baited the city from end to end, killing 900 rats at Lexington Market in a single evening, and well over one million when all was said and done.
Effective? Evidently. Harmless? Not so much. Pets died. Children had their stomachs pumped. And after all that, young rats started to grow wary, eventually avoiding the poison entirely.
Enter the aforementioned Davis, who would take a far more holistic approach into the 1950s. Part of Hopkins School of Public Health, he instead focused on the role of habitat, believing “if you could control the environment, you could control the behavior,” explain Jon Adams and Edmund Ramsden in their new book, Rat City, and thus limit the population size, perhaps even permanently.
His Rodent Ecology Project also coincided with the Baltimore Plan, an urban rehabilitation effort run by the Health Department, which, through infrastructure improvements and code enforcement, intended to address the city’s ailing neighborhoods.