A new study has found that in major cities across the country, warmer temperatures caused by climate change have resulted in rat populations swelling.
The study comes from the journal Science Advances, which studied public complaint and inspection data in 16 cities worldwide to estimate trends in rat populations. Researchers then drew the connection to global warming patterns, marking a first when it comes to climate change and pest populations.
Among the cities examined included Oakland, San Francisco, Buffalo, Toronto, Dallas, Chicago, New York City, Boston, Kansas City, Cincinnati, Tokyo, Louisville, New Orleans, Amsterdam, and Washington, DC.
The report highlighted that in 11 of the examined cities, there was a “significant” increase in rat populations, while only three, Tokyo, Louisville, and New Orleans, saw declines in their populations.
When it comes to why some cities saw increases, researchers noted that denser human populations, a jump in urbanization, and an increase in warmer weather all played a part.
The lead author of the study, Jonathan L. Richardson, an associate professor at the University of Richmond, shared with CBS News that the latter was found to play a large role in the trend.
“We found these cities that have increasing warming trends over the last 50 years or so also have faster number of rats,” Richardson said.
The study shared that the weather can impact a rat’s physiology, leading females to reach sexual maturity earlier, meaning they can reproduce sooner and have larger litters more frequently due to the longer periods of warmth.
The dangers of larger rate populations were also touched on in the survey, with researchers noting that it “impacts people and their psyche” as well as breeding disease.
“They transmit and carry more than 50 zoonotic pathogens and parasites that can make people sick,” Richardson said.
While it may not be easy to deal with the rodents, Richardson noted that cities are trying to curb the rat populations. Still, he noted that rats are “a very smart animal, and it is, you know it’s remarkable at how good it can be at avoiding what we’re using to try to control it.”