A first-of-its-kind examination of trends and reasons in hard-to-count rat populations uses rat sighting reports in 16 cities around the world. Based on individual trends within cities, Washington was by far the leader in rat increases, followed by San Francisco, Toronto, New York City and Amsterdam.
Washington city officials did not respond to requests for comment. Only three cities saw significant decreasing trends โ New Orleans, Louisville and Tokyo โ with the home of Mardi Gras showing the biggest drop in rat reporting. Experts said the Louisiana city can teach others how to combat the rat problem.
And that comes down to sex and food, said study lead author Jonathan Richardson, a biologist at the University of Richmond. An extra month may not sound like much, but female rats can have a litter every month. Researchers pointed to two other big statistical links โ that fit with known biological issues โ behind more rat reports: the increase in urbanization and more densely populated cities.
Rats like the built-up environment and being near people and their waste, the study and outside scientists said. They essentially eat at the same table as humans, multiple experts said. Even though rats are intelligent and highly adaptive, Richardson and other experts said they are a serious problem for people.
Researchers have not had good figures on rats. Because of the way they live and hide, they are not as easily counted as other critters, so this is one of the first attempts to quantify them. The study is not really a count of rats, but of complaints by people. Looking at the few cities where rat reports are down may help in the fight against rats, Richardson and Corradi said. The answer is not more poison or traps, but prevention, the study said.
