Teresa Guerrero Madrid

Madrid

Updated Wednesday, April 3, 2024-19:58

The city of Paris is facing a veritable rat plague. The presence of these rodents inside and outside the sewers is not a new problem in the French capital or in other large cities such as New York or London, but their expansion has become uncontrolled despite the plans put in place to try to reduce their population. which in the French capital is estimated to be between four and six million copies.

If current hygiene and pest control methods have not been able to win the battle against rats and limit their population, imagine how they expanded freely in the 15th century. An investigation has investigated this aspect and has reconstructed how and when two species of rat arrived in America in two different historical periods, and how they spread across the continent, one at the expense of the other. Because despite how widespread they are, they are not endemic to America, but rather arrived there through maritime transport.

The research, published in the journal

Science Advances

,

advances by several decades the arrival in America of the gray rat,

also called brown or Norwegian (

Rattus norvegicus

), and places it around the year 1740. Until now it was believed that this voracious species It had arrived on the continent in the 1770s, but analyzes carried out on archaeological remains have shown that its presence dates back earlier.

Specifically, the team led by Eric Guiry, a researcher at the universities of Trent (Canada) and Leicester (United Kingdom), carried out isotope and tissue analyzes of rodent remains found in 32 settlements in North America (from Canada to the Gulf of Mexico), from different historical periods (from the founding of Jamestown in 1607 to the beginning of the 19th century). They also examined samples taken from the remains of seven ships that were shipwrecked in that region, the oldest from approximately 1550 and the most recent from 1770.

In 1740, when the arrival of the gray rat was estimated, the common or black rat

(

Rattus rattus

) was already fully established in America, a regular passenger on ships that crossed the Atlantic in the 15th century (which is why it is also called rat. boat). According to the authors, the common rat possibly arrived in America in 1492, on Christopher Columbus's first voyage to the continent. It is believed that this animal, originally from Asia, was already in the territory that is now the United Kingdom in the 1st century and in the 8th century it had already colonized. Europe.

The Europeans were the ones who dispersed

this rodent throughout the rest of the planet, which prospered quickly thanks to its great ease of adaptation, which has made it one of the hundred most harmful invasive exotic species in the world.

Two hundred and fifty years after the arrival of the common rat in America, the gray rat, larger and more aggressive, began to compete and eat ground on that continent until, according to the authors, it ended up displacing it in coastal urban centers.

While the gray rat measures about 30 centimeters and weighs between 280 grams and half a kilo, the common rat does not usually reach 20 centimeters and weighs between 75 and 230 grams, depending on the subspecies.

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The authors believe that

the gray rats reduced the availability of food for the common rats

, causing a gradual reduction in the reproduction rates of the species that had arrived before, and the collapse of its population. This is how chronicles of the time describe it, which talk about how they had practically disappeared from American cities in the 1830s.

For Eric Guiry, the remains of rats have great value in archaeological research: "We have this enormous treasure of animals that represent the relationships between humans and animals over hundreds or even thousands of years, depending on where it is found," he points out. the researcher, who believes that "those relationships between humans and animals of the past could tell us a lot about how we could relate to each other in the future, particularly in the context of urban planning."

Specifically, the authors point out that a greater understanding of the ecology of these two rat species has

implications for preventing the spread of zoonoses

(diseases transmitted from animals to people) and for improving the effectiveness of techniques to eradicate pests.

Rats are of concern due to their ability to transmit diseases to people, although not all species transmit the same pathogens. On the other hand, it has recently been questioned whether common rats had spread the Black Death that killed millions of people during the Middle Ages. In a study in the journal

PNAS

, a team argued that human parasites, such as fleas and lice, had been the ones that had spread the bacteria of the second Black Death pandemic.