The Chicago Rat Project

Brown rats (Rattus norvegicus), also known as Norway rats, are perhaps the most successful urban wildlife species in the world. Rats live on every continent except Antarctica and thrive in cities, where they live in buildings and sewers. Rats can damage property by chewing pipes and wires. These rodents also carry many diseases shared with people, including Leptospirosis. To minimize these damages, pest management experts spend billions of dollars annually to manage rats in the U.S. alone.

A better understanding of urban rat ecology will help prevent the risks associated with rats and reduce human conflict with urban wildlife. This is especially important in Chicago because rat complaints are high and increasing over time.

To better understand human-wildlife conflicts with Chicago’s rats, researchers with the zoo’s Urban Wildlife Institute and Davee Center for Epidemiology and Endocrinology are attempting to answer the following questions:

• Are rat complaints a good indicator of where rat control is most needed?
• Why do some neighborhoods have more rats than others?
• Where and when are rats more likely to carry diseases that can spread to people?
• Do rat infestations impact resident physical and mental health and attitudes about urban wildlife?
• How does rodent control change rat populations and disease transmission?

While Chicagoans make many rat complaints, they are not distributed evenly across the city. Zoo research has found that neighborhoods with higher numbers of complaints, more renters, and less vacant land tend to have more rats. Through a partnership with Landmark Pest Management, researchers can measure the abundance of rats by recording the number of rats the business catches per night. Using these relationships, they can predict where rats should be most abundant across the city.

Rats thrive in areas with supplemental food from garbage and where clutter, also known as harborage, provides shelter and cover. Zoo researchers record these habitat features in alleys that are likely to attract rats. The results: alleys with more uncontained garbage tend to have more rats.

A second phase of the project, funded by the National Science Foundation, will investigate:

1. how rat infestations affect resident health, attitudes, and behaviors
2. how rodent control impacts rat population ecology and disease ecology

Zoo researchers will use anonymous surveys and confidential interviews in communities across Chicago to collect information about resident experiences with rats, physical and mental health, attitudes about wildlife, and rodent control behaviors. In partnership with Landmark Pest Management, they will also engage with community scientists to catch rats on their properties. This data will help them link rat infestations with survey responses and identify any public health concerns.

If you would like to learn more about this study, please contact study lead Maureen Murray, Ph.D., at maureenmurray@lpzoo.org.