The long battle between New York residents and their infamous rat and mouse populations could be entering a new phase. A recent study by researchers at Rutgers University concluded that these urban rodents are developing biological and behavioral mechanisms that allow them to resist or evade some of the most used strategies to combat them.

The research, published in the scientific journal Pest Management Science, analyzed DNA samples from house mice and Norway rats captured in urban areas of New York, New Jersey, Pennsylvania and Washington D.C. The results show that a significant proportion of these animals have genetic mutations associated with resistance to anticoagulant rodenticides, one of the most used control methods in the United States.

The scientists focused on the gene known as Vkorc1, related to the rodents' ability to survive exposure to certain poisons. According to the findings, 84% of the mice analyzed carried at least one mutation linked to pesticide resistance, while around 70% had other genetic alterations that strengthen this capacity. In the case of rats, 35% showed a specific mutation related to the same phenomenon.

For researchers, these results reflect decades of evolutionary pressure caused by the constant use of chemicals intended to eliminate urban pests.

Mice develop resistance and rats improve their survival

According to Jin-Jia Yu, lead author of the study, the mice appear to have adapted more quickly due to their exploratory behavior. Their tendency to consume unknown foods, including poisoned baits, would have favored the survival of those individuals with genetic characteristics capable of resisting pesticides.

Rats, for their part, follow a different strategy. Although they also present some mutations associated with chemical resistance, the researchers found evidence that they have developed a remarkable ability to avoid physical traps.

Video records obtained during the study show that many rats manage to identify and avoid snap or sticky traps for days or even weeks. In some cases, the animals avoided activating them after hundreds of contact opportunities. This behavior reinforces rats' reputation as one of the most cautious and adaptable urban animals on the planet, particularly in densely populated cities like New York.

Experts recommend new control strategies

Researchers warn that relying exclusively on rodenticides could become increasingly less effective and lead to unintended environmental consequences. When resistant rodents consume poison and survive, the toxic substances can accumulate in their bodies and reach urban predators such as birds of prey, coyotes and other animals that feed on them. Previous studies have detected traces of these compounds in various wild species.

In addition to the ecological impact, specialists remember that rat and mouse populations represent a public health problem because they can contaminate food, damage buildings and infrastructure, and transmit diseases or parasites.

Given this panorama, the authors recommend a comprehensive strategy based on prevention. Suggested measures include sealing access points to buildings, improving waste management, reducing food sources available to rodents, modifying urban habitats favorable for their reproduction, and selectively using traps.

For experts, understanding how these species evolve will be key to designing more effective control methods in the future. Mientras tanto, la llamada “guerra contra las ratas” en Nueva York continúa, con unos adversarios que parecen adaptarse cada vez mejor a la vida en la gran ciudad.