Researchers have discovered that many rats and mice living beneath major U.S. cities have developed genetic mutations that make them more resistant to common rat poisons.
The findings, from researchers at Rutgers University and highlighted by the Daily Mail, focused on house mice and brown rats commonly found in cities including New York, New Jersey, and Washington, D.C.
After studying nearly 300 rodents, scientists found that around 70% carried mutations in the Vkorc1 gene, which is linked to resistance against anticoagulant rodenticides. The mutations allow many of the animals—particularly house mice—to better survive poisons that have traditionally been used to control their populations.
"Genetic mutation is not that special in these creatures, but we found that the house mouse shows a lot of genetic mutations related to rodenticide resistance," researcher Jin-Jia Yu said.
The researchers also found that brown rats were generally more susceptible to commonly used poisons than house mice, suggesting resistance varies between species.
The findings highlight the growing challenge of controlling rodent populations in urban areas, where traditional poisons may become less effective as resistant animals continue to spread.