If the roasts of heat waves contain destructively.
This is certainly undesirable news for Americans who endure together well over 27 billion US dollars In the value of property damage every year through the hands – and teeth – the rats. This does not include the costs of the diseases that spread the animals, such as: HantavirusPresent Murine typhoid And bubonic plagueStill the Tay fees mental health live among them.
The New knowledgeReports on Friday in the magazine Science Advances, based on recordings about rat views in 16 cities around the world. Unfortunately for humans, their rat populations were expanded in 11 of these cities in the course of the study, while two cities kept stable and only achieved three measurable declines.
So little should surprise that the rodents should thrive. They are perfect for urban environments in which you manufacture your houses in walls, basement and U -Bahn stations and a holiday at garbage, waste water, waste water. Dog droppings And Abandoned pizza slices. The only continent that you have not yet conquered is Antarctic.
A rat in a garbage container in Richmond, va.
(Jonathan Richardson)
“This way is really well adjusted to take food and convert it into new baby rats that scurry in your neighborhood” Jonathan RichardsonBiologist at the University of Richmond, who studies wild animals in cities and their effects on human health. “They make that really efficient.”
One of the few things that slow down the rats is cold weather. And with climate change we have less of it.
Global warming means that average temperatures rise, which reduces the number of winter days. In cities, the trend is reinforced by the fact that the built environment absorbs more heat and retains the rural area around it, a phenomenon known as a city Heat island effect.
In order to examine a possible connection between rat populations and increasing temperatures, Richardson and his colleagues in the 200 most populous cities in the country searched for reliable data. The implementation of a thorough census of rats was impractical – if not impossible -, so they used municipal inspection protocols and rat sightings that were reported to the government agencies.
They found 13 cities that had kept consistent records for at least seven years. Then they widened their search and found three other cities overseas. The final group had rattling data that came back on average a little more than 12 years.
Since the cities used various data sources that were collected over different periods, the researchers have created a standardized method to measure the change in the rat views. They found that rat reports most in the in Washington, DCFollowed by San Francisco, Toronto, New York City, Amsterdam, Oakland, Buffalo, Chicago, Boston, Kansas City and Cincinnati.
Three cities – New Orleans, Louisville and Tokyo – managed to reduce their rat populations during the investigation period. There were no significant changes in Dallas or St. Louis.
Los Angeles was not included in the analysis because systematic rat recordings were not available. La routine Rank under the top three In the annual lists of pest control companies of America's “Rattligest cities”, Richardson, however, said that the constantly large volume of rodent complaints had to do more with the extensive size of the city than with a uniquely rat -friendly environment.
Next, the researchers used statistical methods to determine which factors could blame the differences in the rat control results of the cities. About two thirds of the variation could be explained by five things, including the human population density and the amount of areas covered by vegetation.
The most important factor was to change the average temperature of a city – the more it rose, the more the rat population grew.
A rat crosses a U -Bahn platform on the New York Times Square.
(Richard Drew / Associated Press)
The change in the minimum temperature of a city had no influence on rats. Richardson said the team was initially surprised because the cold weather extends the time, the female rats become fruitful and reduce the number of puppies in a trash.
In the more hospitable weather, a rat can get pregnant if it is only two months old, and this pregnancy will only take three to five weeks. The researchers realized that when rising average temperatures arrived a week later and entering a rat a few weeks later, a rat could buy enough time to press an additional reproductive cycle every year, said Richardson.
Santtu penticeseA researcher at the University of Helsinki, who was not involved in the work, said that the authors of the study had a convincing case that global warming was good for rats.
“The results only make sense,” said Pentikäinen, a member of the Helsinki Urban Rattenprojekt.
Co -author Maureen MurrayAn ecologist for wildlife diseases in the Lincoln Park Zoo from Chicago and Fiihrer der Chicago rat projectShe hoped that the results will “motivate people to take care that climate change could make their rat problems worse.”
But Richardson said he was not sure whether the prospect of “more rats, who shine around” sadly polar bear float on ice. “