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In an attempt to decrease the population of rats in New York City, pest control have managed to create a new generation of “super rats.”

According to Jonathan Richardson, from the University of Richmond, although pest control removes most of the rats in a population, the rats that survive the lethal control are genetically more “fit.”

Jonathan, who studies urban rats in New York City, has found that the survivors are more likely to have traits that make them able to avoid the onslaught of exposure to rodenticides and traps.

These survivors then produce baby rats, which inherit the same helpful traits.

Jonathan explained: “If only the fittest rats make it through the control campaign, the survivors may be even better adapted to take advantage of the high-resource minefield of modern cities, leaving a new population of “super rats” to breed and repopulate.”

(Image: Getty Images/iStockphoto)

Some scientists have since identified specific genes in the “super rats” that render common rodenticides ineffective.

Despite the millions of dollars spent annually to combat rats in the city their numbers seem to constantly increase.

Most of the rat populations rebound quickly after a control campaign ends - a phenomenon known as the “boomerang effect.”

An intensive eradication campaign in Salvador, Brazil in 2015, succeeded in cutting the rat population in half but led to a 90% reduction in the genetic variation contained in those populations.

(Image: Getty Images/iStockphoto)

This culling led to the loss of many of the rats' rarest gene variants and since the survivors were more likely closely related to each other, there was a greater risk of inbreeding.

The problem is that there is rarely coordination between pest management staff working with cities or property owners, often with short timelines and insufficient budgets, and scientists interested in tracking the long-term viability of urban pest species.

(Image: Getty Images/iStockphoto)

As the environmental health coordinator for the city of Somerville, Massachusetts, Georgianna Silveira is on the front line of efforts to integrate pest management and policy decisions with a scientific perspective on long-term trends.

“In a practical sense, it’s about putting out fires with quick solutions often because there is too little communication among residents, city agencies, pest management professionals and scientists about sustained goals," she said.