There is a saying that in a large city you are never more than two meters from a mouse. It is an urban myth, but scientists are warning that cities around the world are becoming much more infested with rats, and the increase is mainly driven by a factor: climate change.
Jonathan Richardson, professor of biology at Richmond University, decided to research urban rats trends after seeing media reports on rats taking over the cities. These reports tended to focus on specific locations and “usually without much concrete data,” he said CNN.
He and his team decided to change that. They requested data on rats from the 200 largest US cities by population, but found that only 13 had good quality long -term data they needed. To expand geographical scope, researchers also included three international cities: Toronto, Tokyo and Amsterdam.
The data collected covered an average of 12 years and included sightings of rats, capture and inspection reports.
The results revealed “trends of significant increase” in the number of rats in 11 of the 16 cities, according to the study, published on Friday (31) in the magazine *Science Advances *. Washington DC, San Francisco, Toronto, New York and Amsterdam experienced the highest growth. Only three cities saw falls: New Orleans, Louisville and Tokyo.
The study associated the increase of rats with several factors, including high population densities and low urban vegetation, but the main influence was the increase in average temperatures.
Rats are small mammals and cold -limited by the cold, Richardson said. Higher temperatures, especially in winter, offer them more time away from home to seek food and crucially more time to reproduce throughout the year.
A warmer climate can also prolong growth seasons, providing more food and vegetation for mice to hide, said Michael Parsons, an urban field ecologist and wild rats, who did not participate in the research. “Even food and garbage odors can travel further in a warmer climate,” he told CNN.
Increased rat populations is a big problem for cities. Rats damage the infrastructure, contaminate food and can start fires at the role wires. They cause estimated $ 27 billion damage each year in the US, according to the report.
They also pose a health risk. “Rats are associated with more than 50 pathogens affecting people,” which are transmitted through urine, feces, saliva, nest materials and parasites, said Matt Frye, a cornell university specialist, who did not participate in the research .
Some of these pathogens may be serious, such as leptospirosis, also called Weil’s disease, which can cause damage to the kidneys and liver and even untreated death.
There are also growing evidence that rats have “major impacts on mental health” of people living around them, Richardson said.
Even among the most infested cities of rats identified in the study, Washington, DC, stood out. It has increased 1.5 times higher in the rat population than New York.
The most evident sign of a problem with DC rats is a hole rolled into a tin of rigid plastic garbage. “The only way to make a trash can rodent is not putting food on it,” said Gerard Brown, responsible for the town’s rodent control program.
Last year was the hottest ever recorded in DC – bad news for attempts to control the rats. Brown expects the cold wave in December and January to help reduce the population. “The cold acts like a natural exterminator,” he said.
Brown and other city officials have tried a rated birth control pilot project a few years ago, but abandoned it after inconclusive results. Rats needed to consume contraceptive liquid daily, an impossible task to ensure.
Brown said the numbers of DC mice can be so high because the city encourages residents to report each mouse sighting.
Public reports about rats are very useful, but they can be flawed, said Campo Parsons ecologist. People usually only make a complaint when they see something “unusual,” he said, not when rats are expected in a certain area.
It is extremely difficult to determine precise numbers of urban rats, Parsons added. “The rats are small, discreet and usually nightly.”
Richardson said the large number of rats in some cities is not a reflection of the authorities’ commitment to solve the problem, but efforts to reduce the population of mice are usually sub -financed.
Lessons can be learned from the three cities of the study that reduced rat populations, he said. He attributes the success of these cities to campaigns that informed residents on how to avoid attracting rats and made the city’s resources available to help.
Richardson also encouraged authorities to move away from lethal control, “because this is just a response to infestations that already exist” and thinking more about how to get access to what mice depend, such as food waste, access to trash and batteries of rubble.
The results are a warning about the challenge that rats can represent in a warmer world, Richardson said. “If you have no control over it, it will only get worse. You don’t want to be like a sishyphus pushing that stone I die above. ”
In DC, Brown said he was optimistic about the city’s battle to keep the mice under control. “No one in the world thinks we’ll get rid of the mice, but we can reduce them to an administrable level,” he said. “The goal is to control and reduce.”
