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Study Reveals Record Increase of Rodents in 11 Major Cities, With Increases of Up to 400% and Failures in Traditional Control Methods.
In recent years, several cities around the world have recorded accelerated growth in rat populations. Environmental changes and the daily habits of urban residents are among the main causes of this phenomenon.
In many homes, finding traces and damage caused by rodents has become common, raising concerns about public health and family well-being.
A study published in Science Advances earlier this year analyzed infestation records and environmental conditions in 16 cities over more than a decade. The results showed a significant increase in activity and the number of rats in 11 of them.
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Growth and Global Reach of the Problem
Cleankill, a pest control company, reported a 20% increase in rat activity over the past two years in southern England.
Clive Bury, the company’s founder, stated that the phenomenon is not restricted to one city. The British Pest Control Association (BPCA) confirmed that more than half of pest control services received more calls about rats since 2019.
Data from Drain Detectives, cited by the BBC, indicate that over half a million infestation cases were reported to local councils in the UK between 2023 and mid-this year.
Estimates suggest that the rat population in the country ranges between 10 and 120 million. However, the problem is not limited to the UK.
Major cities in the United States, such as Washington, D.C., San Francisco, and New York, are also facing significant increases, as are urban centers in Canada and the Netherlands.
Health Risks and Environmental Factors
The growing presence of rats poses direct health risks. Experts consulted by the BBC warn that, even in seemingly clean environments, these animals transit through sewers and trash bins, facilitating the transmission of serious diseases.
Among the main diseases are leptospirosis, caused by rodent urine, and hantavirus, transmitted through inhalation of particles from dried feces.
Expert Bobby Corrigan, a researcher of rat behavior in urban areas, explained that the expansion of species is linked to factors such as the constant availability of food scraps—especially due to fast food consumption—irregular garbage collection, and construction work that affects sewer systems.
According to the BPCA, increasing urbanization, changes in waste management, and infrastructure development enhance rats’ access to food and shelter. The climate issue also plays a central role.
Research conducted by Corrigan and the University of Richmond shows that rising temperatures are directly associated with the growth of the rat population. Among the cities analyzed, Washington, D.C. showed a 400% increase, San Francisco 300%, Toronto 180%, and New York 160%.
The Role of Climate and Urbanization
Experts explain that milder winters allow rats to remain active for longer periods. Urbanization intensifies the problem through the heat island effect, where asphalt and buildings retain more heat than rural areas.
The Climate Action Tracker projects that global warming could raise temperatures by 1.9℃ to 2.7℃ above pre-industrial levels by 2100—a scenario that further favors the survival and reproduction of these animals.
A pair of rats can produce over a thousand offspring per year, according to researchers. This reproductive capacity, combined with warm weather and the availability of trash, accelerates the multiplication of colonies in urban environments.
Resistance to Poisons and Ethical Dilemmas
Professor Steven Belmain from the University of Greenwich highlighted that rats exhibit “neophobic” behavior, meaning they distrust new foods, making conventional poisons less effective. Dr. Alan Buckle from the University of Reading added that traditional extermination methods, such as anticoagulants, face another challenge: genetic mutations have made many rats resistant to these products.
Moreover, the use of these poisons causes prolonged suffering and raises ethical dilemmas. In light of the ineffectiveness and ethical concerns, cities like New York have sought new approaches.
Urban Strategies and Preventive Measures
In New York, former rat control agent Kathleen Corradi led educational programs and preventive measures. The main focus has shifted to public awareness. The initiative teaches best practices, such as reducing outdoor trash and storing waste in rodent-proof containers.
To ensure compliance with the rules, the city created a system of inspections and fines. The goal is to cut rats’ access to their main food source.
Experts and pest control companies agree that combating urban infestations requires integrated actions. The use of poisons alone does not solve the problem while there is poorly managed trash and waste feeding the proliferation.
Future Outlook
With population growth in cities, the problem is likely to intensify. The UK’s Office for National Statistics predicts that the country’s population will increase from 67.6 million in 2022 to 72.5 million in 2032. This rise represents more waste, more construction, and more opportunities for rats to expand.
In light of this scenario, experts emphasize that effective control depends on a combination of consistent public policies, efficient waste management, and changes in urban habits. The challenge is global—and so far, solutions are still playing catch-up with the rats.
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