Brown Rats Arrived in America Earlier Than Thought

Brown rats are the undisputed winners of the real rat race. New research suggests that they crawled off ships arriving in North America earlier than previously thought and out-competed rodent rivals, per the AP. 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 only a matter of decades," said Michael Buckley, one of the authors of a new study published 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 who was not involved with the study. Neither rat species is native to North America, said Buckley, of the UK's University of Manchester. Scientists used to think that 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 shipwrecks.

The data suggests that 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. One probable reason they dominated, researchers suggest, is that they ate food black rats would otherwise have consumed. Historical anecdotes back up this finding, describing the near disappearance of black rats from cities in the 1830s. Today, both types of rats exist in North American cities, though brown rats are more prevalent. (New York City has even hired a "rat czar.")