Rising Rat Populations and Shifting Control Strategies Amid Global Heating

A recent multi-city study led by Dr Robert Corrigan and nine colleagues documented a dramatic increase in rat abundance across 16 cities, linking the rise to higher winter temperatures. The two most common species—black and brown rats—do not hibernate, so milder winters allow continuous breeding. Corrigan notes that even modest gains in reproductive output, when multiplied across “hundreds of millions of rats,” can overwhelm municipal pest programs.

The Guardian

Traditional reliance on rodenticides is increasingly questioned. Experts cite the “band-aid” nature of poison, its cruelty, and collateral harm to wildlife and humans—thousands of accidental poisonings are reported annually in the United States. Richard Parr, director of the UK charity the Center for Wild Animal Welfare, argues that developing contraceptive technologies is essential for managing “poison-resistant rats compassionately.” However, University of Greenwich ecologist Steven Belmain warns that fertility controls are not yet practical for indoor infestations, emphasizing that restaurants, hospitals and food warehouses still depend on chemical measures.

The Guardian

Alberta, Canada, stands out as a rare example of near-total rat suppression. Since a provincial program began in 1950, the government has combined legislation requiring property owners to report rodents with extensive public-education campaigns. The approach relies on community participation rather than large-scale poisoning. Nonetheless, recent warm autumns and increased tourism threaten to reintroduce rodents, prompting officials to monitor sanitation challenges in expanding urban areas.

The Guardian

Corrigan emphasizes that rats are “smart mammals with mammal brains,” urging municipalities to move beyond treating them as generic vermin. He advocates for stricter public-health regulations and research into fertility-based control as longer-term solutions. Alberta officials credit mandatory reporting and education for their success, while acknowledging that climate-driven milder winters could erode these gains.

The Guardian

• “The rodents have paid for every single bill I’ve ever had – every mortgage, every car payment, every pint of Guinness,” — Dr Robert Corrigan

The Guardian

• “Developing new forms of birth control is the key to managing the soaring number of poison-resistant rats compassionately,” — Richard Parr, director of UK charity the Center for Wild Animal Welfare

The Guardian

• “There was a rat patrol that went out and started eradicating all the infestations along the border. At that time there were probably six or seven hundred infestations a year,” — Wickerson. In

The Guardian