Efforts to control urban rat populations rarely — if ever — result in the complete eradication of the pests. Most of the time, the goal is to simply reduce rodent numbers enough to minimize the spread of disease or damage to property.
But according to Jonathan Richardson, an assistant professor of biology at the University of Richmond, letting some rats slip through the cracks can cause a local population to swiftly evolve, leading to either of two long-term outcomes: sickly rats or “super” ones.
Rats are being artificially extinguished at a rate that catalyzes the evolutionary process known as natural selection. In large cities, such as NYC, or Brazil, pesky rodent populations are frequently targeted for extermination with warfarin. A an extremely deadly and potent poison which essentially causes liver failure in mammals. The chemical is so deadly, and so toxic in fact, it has been used to the target feral hog problem in parts of Texas (despite the lack of an EPA approval). Which is extraordinarily dangerous, because warfarin can bioaccumulate and kill grazing livestock and cattle, and could ultimately end up in your food.
As the breeding pairs of genetically diverse rats dwindles in these urban cities to a smaller and smaller pool, one of two scenarios will unfold for the rat populations:
Urban rat populations could become extremely weak, diseased and in-bred. In this scenario, it could lead to a total eradication of rats.