Brown rats arrived in North America earlier than previously thought and out-competed black rats, becoming the dominant species on the East Coast in a matter of decades. The new study, published in the journal Science Advances, analyzed rodent bones from 32 settlements in eastern North America and the Gulf of Mexico dating from the 1600s to the 1900s. Another focus of the study was on seven shipwrecks dating from about 1550 to 1770. Researchers suggest that brown rats arrived in North America via shipping networks across the Atlantic Ocean, positioning themselves in coastal shipping centers.
Brown rats are larger and more aggressive than black rats, making them more successful in competing for resources near human populations. They are known for spreading diseases such as leptospirosis, murine typhus, and salmonella. Despite the presence of both black and brown rats in North American cities, brown rats are more prevalent. Efforts to control rat populations in cities include reducing available food waste, as brown rats are especially fond of animal products. This research sheds light on the history and behavior of rat populations in urban environments, helping cities better manage pest control measures.
Historical anecdotes describe the near disappearance of black rats from cities in the 1830s, supporting the idea that brown rats out-competed them for resources. Researchers believe that brown rats dominated by eating food that black rats would have otherwise consumed, potentially reducing black rat reproduction. These findings contribute to a better understanding of rat populations in urban areas and how to effectively manage them. The identification of brown rats’ preferences for low, ground-level habitats compared to black rats’ preference for higher spots helps inform pest control strategies in cities.
Urban centers such as New York City are facing an increasing rat problem, with brown rats being the primary concern due to their potential to spread diseases. The city hired a “rat czar” in response to the growing rat population. Efforts to prevent rats from accessing food sources, such as reducing available food waste, are seen as effective measures to control rat populations. By understanding the behaviors and preferences of different rat species, cities can implement targeted strategies to reduce rat populations and minimize the risk of disease transmission.
Brown rats are commonly referred to as common rats, street rats, or sewer rats due to their prevalence in urban areas. They quickly established dominance on the East Coast of North America, pushing aside black rats that had arrived earlier. Despite being non-native species, both black and brown rats have adapted to urban environments and continue to thrive. By pinpointing the arrival of brown rats in North America earlier than previously thought, researchers can paint a more accurate picture of the history of rat populations and how they have impacted cities over time. This knowledge can inform future pest control efforts and help prevent the spread of diseases carried by rats.
