While the name of John Bumpass Calhoun might not be familiar to everyone these days, he and his life’s work — studying rats and mice — were grounded here in Baltimore at the Johns Hopkins University in the 1940s and 1950s, when the city was dealing with a rat problem.

What has brought Calhoun from relative obscurity and into relevance is the publication this summer of “Rat City,” by authors Jon Adams and Edmund Ramsden.

Calhoun, a Tennessee native who graduated from the University of Virginia in 1939, and earned his master’s and Ph.D from Northwestern University, was by trade a biologist, psychologist, population researcher and an ethologist, one who studies the behavior of animals in their natural habitat.

The City of Baltimore turned to Calhoun for solutions when he joined the Rodent Ecology Project at what is now the Johns Hopkins Bloomberg School of Public Health in 1946.

City officials, fearing that typhus would be spread by rats carrying fleas, enlisted the help of Calhoun, who turned city streets, alleys and backyards into his laboratory.

While poisoning reduced the rat population temporarily, they always returned to their former numbers.

Calhoun trapped and tagged the rodents, and then released them to study their movements. He soon discovered that well-meaning citizens scalding the rats with boiling water or killing them in other ways interfered with his studies.

So, instead, he resorted to building a ¼-acre, fenced, 10,000-square-foot pen for his rat colony behind his Towson home. He introduced five pairs of Norway or brown rats and let them live in the wild while he observed from a 20-foot tower for 27 months.

They were free of disease and predators, had unlimited access to food, and organized themselves into colonies of a dozen rats each.

What Calhoun deduced was the effect crowding had on behavior and how it ultimately led to the social order breaking down.

“His findings led to the concept of the ‘behavioral sink’ and suggested that evolution had given animals, perhaps including humans, an innate and irreversible self-destruct button to prevent a species from overpopulating its habitat,” wrote Fredrick Kunkle in his Washington Post article, “The researcher who loved rats and fueled our doomsday fears.”

Calhoun began studying mice at the Jackson Memorial Laboratory in Bar Harbor, Maine, before joining the National Institutes of Health in 1954 as a research psychologist.

As he had done in his Towson backyard, Calhoun took eight white mice, four pairs, and put them into an enclosure at the NIH’s animal farm in Poolesville, Maryland, and within two years, the population had grown to 2,200, before the die-off began.

At first, 600 died, leaving 1,600 mice that he predicted would also die. Calhoun believed they had evolved into what he termed “non mice,” as a result of social disintegration, which meant the end of the colony.

“Amid such profound squalor and chaos, the mice forgot how to be mice. They ceased to breed, and their population collapsed,” Kunkle wrote.

“It was a disturbing vision that seemed to echo the human experience of millions in America’s cities. Calhoun fanned the pessimism, making specific predictions that if humans failed to slow their exponential rate of population growth, a similar extinction could befall them by 2027,” he wrote.

“Among other findings, he developed the concept of universal autism — in which all members of the last generation of mice in an increasingly crowded environment are incapable of social behavior that would allow them to produce the next generation,” The Baltimore Sun reported at Calhoun’s death in 1995.

“He also described a phenomenon in which some mice become ‘beautiful ones,’ maintaining their physical appearance, but doing little else as the population swells.”

In Baltimore, the Department of Public Works’ Rat Rubout program, a rat eradication program that began in 1972, answers 250,000 service calls a year, The Sun recently reported.

Have a news tip? Contact Frederick N. Rasmussen at frasmussen@baltsun.com and 410-332-6536.