Global rat populations are increasing due to warmer winters, according to a paper published last year by Dr Robert Corrigan and 10 other scientists. Their research across 16 cities found a dramatic rise in rat numbers, correlating with rising temperatures.
Dr Corrigan, a rodentologist, explained that the two most common types of rat, black and brown, do not hibernate. This means that in areas with regular cold winters, their reproduction typically slows or stops. However, repeated warm winters offer rats a marginal advantage, which escalates significantly when multiplied across millions of rats.
While rats can carry diseases like Weil's disease and hantavirus, and decimate crop yields, experts are increasingly seeking alternatives to traditional poisons. Methods under consideration include fertility controls and robust public health regulations.
Richard Parr, director of the UK charity the Center for Wild Animal Welfare, stated that developing new forms of birth control is key to managing poison-resistant rats. However, Professor Steven Belmain of the University of Greenwich expressed scepticism about the current advancement of fertility controls, suggesting they are not yet a viable solution for immediate infestations in critical environments like restaurants or hospitals.
Dr Corrigan believes that rat infestations often stem from a failure of municipal politics and poor sanitation habits. He points to Alberta, Canada, as a successful example of managing rat populations through collective effort and a proactive programme operational since 1950, which has resulted in a negligible rat population.