They are not only the kings of Wrocław. Rats with a costly problem in Western cities

In many western cities, the problem of rats is growing, which in a favorable climate reproduce faster than ever – according to research published in Science Advans. The increase in the number of rodents record, among others Amsterdam, Toronto and New York, and experts warn that the phenomenon may deepen with the insulation of the climate and the growing mountains of waste in cities.

Over the past decade, the number of rats in some metropolises has increased several times – in Washington by 390 percent, in San Francisco by 300 %, and in Toronto by 186 percent. The authors of the study emphasize that similar trends also apply to European cities, although the scale varies depending on local conditions. In Amsterdam, where the problem is particularly visible, in 2024 about 6,800 cases were reported, where the rat appeared in the apartment or, for example, a restaurant or store – 600 more than a year ago.

According to scientists, rising temperatures extend the rodent breeding period and reduce their mortality in winter. “This is the most disturbing conclusion of the study – where the climate warms faster, the number of rats is growing faster,” comments prof. Jonathan Richardson from the University of Richmond.

Local media reports about spectacular events involving rats. In Arnhem in the Netherlands, the rodents displaced families from the apartments, and in England there were individuals whose body length reaches 56 cm, thus reaching almost the size of the cat. In Berlin, the authorities impose high fines for throwing kebabs on the street, which are a delicacy of rodents. In Paris, the number of rats is estimated at over four million, which has long been concerned about the inhabitants.

In a study from 2024, published in the magazine Urban Ecosystems by de Cock et al. Rats (Rattus Norvegicus and R. Rattus) were caught in three Dutch cities – Amsterdam, Rotterdam and Eindhoven. It was found that a larger amount of urban greenery (measured by the NDVI indicator, restaurants and mini-zoo) correlates with greater number of rats. The authors suggest that green areas offer both food and shelter, which promotes the growth of rat population.

Experts emphasize that the problem mainly results from human activities. “This is not a problem with rats, but with us – with how we store food and waste,” says Floris Hoefakker from the Dutch Staatsbosbeheer. According to him, people themselves “develop a red rug” for rodents, leaving open garbage bins or leaky sewage installations.

Rats are not only a sanitary threat – they carry over 60 diseases, including leptospirus and dumbbells – but also psychological. Studies indicate that frequent meetings with rodents reduce the well -being of city residents.

Despite the bad reputation, some researchers remind you that rats are intelligent and social animals. “These are very empathic beings who – just like us – are simply looking for food,” notes Maite Van Gerwen's biologist, criticizing the demonization of the species.

Scientists indicate that the fight against the scourge should be based not on mass threshing, but on limiting the attractiveness of cities for rodents – e.g. by better protection of waste and education of residents. “Every city declares war to rats, but to win it, you need to know what opponent we have before us,” sums up Richardson.

Patryk Kulpok (PAP)

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