How brown rats crossed oceans and conquered cities
Brown rats are the winners of the real rat race.
New research suggests they crawled off ships arriving in North America earlier than previously thought and out-competed rodent rivals — going on to become so ubiquitous they’re known as common rats or street rats.
It didn’t take long for them to push aside the black rats that had likely arrived with Columbus and thrived in colonial cities.
After first appearing on the continent before 1740, brown rats took over the East Coast from black rats “in ... a matter of decades,” said Michael Buckley, one of the authors of a study published Wednesday in the journal Science Advances.
Brown rats are larger and more aggressive than black rats — and they want to be close to human populations, said Matthew Frye, a researcher with the New York State Integrated Pest Management Program at Cornell University.
From this research, “we know a more exact time of when they arrived and ... what they were doing once they got here,” said Frye, who was not involved with the study. “Having that picture of the rat population helps us ... understand what they’re doing and maybe how we can manage them.”
Neither rat species is native to North America, said Buckley, of the University of Manchester in the United Kingdom. Scientists used to think brown rats arrived around 1776. The new study pushes that date back by more than 35 years.
Buckley and his colleagues analyzed rodent bones that had already been excavated by archeologists. The remains came from 32 settlements in eastern North America and the Gulf of Mexico dated from the founding of Jamestown in 1607 through the early 1900s. Other samples were from seven shipwrecks dating from about 1550 to 1770.
The data suggests shipping networks across the Atlantic Ocean “essentially functioned as rat superhighways,” with brown rats gaining their earliest footholds in coastal shipping centers, said Ryan Kennedy, a study author at Indiana University who researches animal remains at archaeological sites.