David E. Davis was an ecologist and animal behaviorist noted for being the "founder of modern rat studies" .

He received a BA at Swarthmore College

Swarthmore College

Swarthmore College is a private, independent, liberal arts college in the United States with an enrollment of about 1,500 students. The college is located in the borough of Swarthmore, Pennsylvania, 11 miles southwest of Philadelphia....

 in 1935, then an MS and PhD at Harvard University

Harvard University

Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...

 in 1939 . His career included 13 years as Assistant Professor at Johns Hopkins

Johns Hopkins University

The Johns Hopkins University, commonly referred to as Johns Hopkins, JHU, or simply Hopkins, is a private research university based in Baltimore, Maryland, United States...

 School of Hygiene and Public Health where, among other works, he started the Rodent Ecology Project. Through systematic research he debunked the myth of 1 rat per person in NYC, and placed the rat population at about 250,000.

He later became a Professor at Pennsylvania State University

Pennsylvania State University

The Pennsylvania State University, commonly referred to as Penn State or PSU, is a public research university with campuses and facilities throughout the state of Pennsylvania, United States. Founded in 1855, the university has a threefold mission of teaching, research, and public service...

, then Chairman of Zoology at North Carolina State University at Raleigh. During his career he published 3 books and 230 papers.