Popular urban legends allege that rats in New York City outnumber humans by as much as four to one. A study in 2014 found the opposite to be true - humans outnumber rats four to one. But that still meant the city is home to approximately 2 million rats at the time of the study. Understandably, this number is still much too high for anyone's tastes.
To stop the rat epidemic, the city has tried many of the usual attempts - poison and traps, to no avail. Now, they're deploying the big guns: rat contraceptives known as ContraPest. The compound induces permanent menopause in female rats, which would prevent future baby rats. Whereas poisons and traps work on very small populations of rats and could encourage other populations to thrive, the contraceptives will be more effective and long-lasting at controlling the pest population. The compound will be tested first in a few residential areas around the city.