The movement of rats, stealthy and often unwelcome inhabitants of our urban landscapes, have long intrigued scientists and city dwellers alike. Now, research published in Science Advances sheds light on the pervasiveness of their colonization of human settlements and related implications for urban planning and public health.  

The study, co-authored by Dr. Eric Guiry, adjunct professor of Archaeology at Trent, delves into the historical rise and dominance of two species – the black and brown rat. It’s well established that the presence of black rats predates their brown counterpart in North America. However, findings from Professor Guiry and the rest of the research team indicate brown rats arrived on the continent much earlier than previously thought.  

"Our findings challenge conventional beliefs, showing that the dynamics between black and brown rats, as well as their interactions with humans, are more intricate than previously understood." says Prof. Guiry. “Our findings, pertaining to rat dietary preferences, can guide urban planners toward more efficient food waste strategies; specifically reducing the availability of animal products in urban hubs in order to reduce rat presence in these areas.” 

The research group studied rat bones from various locations, including the Atlantic Ocean floor. Shipwrecks are particularly valuable for determining timing as historical records tell us exactly when and where ships sank. In this way, the researchers could precisely trace the movement of rodent populations entering the Eastern coasts of North America and were able to determine that brown rats swiftly displaced black rats as the dominant rat species on the continent. 

Suggesting that diseases associated with brown rats may have played a more significant role in North America’s history over the past 250 years compared to those associated with black rats, the study helps to contextualize the historical spread of zoonotic diseases from rats to humans, and how this information can be used when shaping public health policies.  

This research is a significant step forward in unraveling the complexities of urban rat colonization and its implications for society. As cities grapple with mounting challenges around coexisting with rodent populations, this study provides insights that could help inform the future of urban planning. 

Learn more about the research, featured in Scientific American, Washington Post, Popular Science and on CBC Radio and the Science Journal Podcast.