Rodents in New York City are evolving to counter human pest control strategies, with house mice developing genetic mutations that provide immunity to pesticides and rats becoming increasingly skilled at avoiding traps, a recent study reveals.
The research, conducted by Rutgers University scientists Jin-Jia Yu and Changlu Wang, involved sampling DNA from 300 house mice and Norway rats in densely populated urban areas across New Jersey, Pennsylvania, Washington D.C., and New York. The findings indicate that these urban rodents are adapting to decades of human efforts to control them.
Evolving Resistance in Mice
According to the study, approximately 70% of the house mice sampled possessed a genetic mutation that renders common anticoagulant rodenticides ineffective. These poisons, widely used in pest control, are designed to inhibit blood clotting. However, mice that ingest them can still function normally due to this mutation, allowing them to survive exposure.
"When the mice eat the poison, they can still function normally, basically. That’s why they are more tolerant," explained Wang, an extension specialist in the Department of Entomology. This immunity is thought to have developed over time as mice, driven by curiosity, consumed bait containing poisons.
Rats' Increasing Cunning
While rats are not evolving the same resistance to rodenticides at the same rate, they are exhibiting heightened intelligence and behavioral adaptations to evade physical traps. Researchers observed rats in the Bronx, particularly, demonstrating a sophisticated ability to avoid snap traps and sticky traps commonly used by pest control professionals.
"We have a lot of video clips showing that the rats can avoid the physical traps, like snap traps and sticky traps, which are used very frequently by pest control professionals. They can spend one week or 300 approaches before they even touch the traps," Yu stated.
Broader Implications of Rodent Adaptations
The study's findings suggest that cities may need to reassess their current rodent control methods. The continued reliance on rodenticides, while potentially ineffective against resistant mouse populations, also poses risks to other urban wildlife. Predators like birds and coyotes that consume poisoned rodents can ingest the toxins, leading to secondary poisoning.
"There are studies showing that all of the wild animals that eat roadkills, they contain rodenticide poisons," Wang noted. "It’s more likely to be transferred to the predators."
Furthermore, unchecked rodent populations can lead to future public health concerns, including the contamination of food supplies, damage to infrastructure, and the spread of diseases and parasites. The researchers recommend that city leaders explore non-chemical extermination methods, with an emphasis on prevention and sanitation, to manage rodent populations more effectively and sustainably.