Anticoagulant rodenticides, the chemical poisons cities around the world use to manage rats, cause a slow death from internal bleeding. But they harm more than rats: wild animals that eat poisoned rats or the bait itself can become ill or die. Studies have found traces of these poisons in more than 90 wildlife species, with the poisons contributing to population declines in some threatened species, while thousands of children and dogs are accidentally poisoned each year.
Because anyone can buy these products from hardware stores and major retailers without training, understanding why people choose poison over other methods is crucial to reducing harm. New research published in the journal Cities and the Environment examined this very question in Chicago.
The researchers sent invitations to participate to 4,644 households across different income levels and received 446 complete responses. They then conducted in-depth interviews with 50 respondents to hear, in their own words, why they used or avoided rat poison. The study measured residents’ attitudes toward rats using a previously validated scale, their views on wildlife, how serious a problem they considered rats on their block, and demographic information such as age, gender, income, housing type and whether children, dogs or cats lived in the home.
Nearly 39% of respondents had used rat poison at least once in the previous six months. It was less common than cleaning up their property (72%) or patching rat holes (50%), but more common than using traps (33%) or hiring a rodent control professional (27%). Yet despite its widespread use, rat poison was the method residents were least likely to rate as “extremely important” among all the options. Only 30% of respondents gave it that rating, compared with 76% for cleaning up rubbish.
How people felt about rats mattered more than how many rats they had actually seen. Attitudes toward rats had the strongest association with how important someone considered rat poison, and this in turn had the strongest association with whether they had used it. Concern about rats spreading disease was also strongly associated with seeing poison as important, second only to general attitudes toward rats. By contrast, seeing more rats in the neighbourhood was not significantly associated with poison use, while the subjective perception that rats were a “big problem” was.
Residents earning less than $50,000 a year were also more likely to have used rat poison. A general appreciation of wildlife did not affect poison use, although support for lethal wildlife management showed a small but significant association. This suggests that residents do not connect their general appreciation of wildlife with the harm rat poison causes these animals.
In the interviews, the most common reason residents gave for using poison was simply that they did not know what else to do (10 of the 41 participants who discussed the issue). Others said they wanted to avoid direct contact with rats or felt pressure from neighbours to take part in control efforts. Those who avoided rat poison almost always cited safety concerns, most often about the environment, including soil and water contamination.
The study has limitations: compared with Chicago’s general population, the sample was skewed toward white respondents, women and people with higher incomes, and because it focused on a single US city, the findings may not apply to other communities or countries.
Nevertheless, the researchers argue that reducing rat poison use is not primarily a matter of proving that it does not work, since residents already rate it as the least important method. The greatest opportunity lies in addressing fear and convenience.
Because negative attitudes toward rats were the strongest factor driving use, the researchers recommend replacing language of fear and hostility, such as “the war on rats”, with neutral, factual messages. Since concern for pets, particularly dogs, was high, while a general appreciation of wildlife did not reduce use, campaigns could make an explicit link between rat poison and the harm it causes these animals.
Advocates could also push for stronger restrictions on public access, such as limiting sales to licensed professionals, building on the momentum already present in states such as California and provinces such as British Columbia. Providing accessible alternatives can also help: in a separate study in Cape Town, South Africa, when households were given traps and training, 84% said they would continue using traps instead of turning to pesticides. Given that many Chicago residents said they simply did not know what else to do, making humane alternatives as convenient as poison may protect more animals than simply warning about the risks.
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