New Study Shows Increases in Rat Populations Around the Globe are Linked with Warming Temperatures and Growth of Cities
The research is led by University of Richmond biology professor Jonathan Richardson.
UNIVERSITY OF RICHMOND — A new research study led by University of Richmond biology professor Jonathan Richardson shows that increasing rat numbers in cities around the world are linked to a warming climate and growth of cities.
Richardson and his research team analyzed public complaint and inspection data from 16 cities around the world finding a strong link between rising rat numbers and three key aspects of the urban environment: human population density, urbanization, and warming temperatures.
Key findings in the study out today include:
- 11 of 16 cities (69%) had significant increasing trends in rat numbers, including Washington D.C., New York, and Amsterdam.
- Only three cities experienced decline, including Tokyo and New Orleans.
- Cities experiencing greater temperature increases over time saw larger increases in rat numbers.
- Cities with more dense human populations and more urbanization also saw larger increases in rats.
All of these factors create significant challenges for municipalities and pest management professionals working to control rat populations, and they will need to incorporate these factors into their management strategies.
“The most concerning of these connections we found is the link between climate warming and rat trends, as global temperatures are beyond the control of individual cities,” said Richardson.
Temperature increases may be expanding the seasonal activity periods for rats, allowing them to stay active longer into the winter and to begin foraging aboveground for food resources earlier in the spring.
“Even an extra week or two of aboveground activity for wild rats can translate to one or two more reproductive bouts, accelerating population growth,” Richardson said. “Those working to manage rat populations will need to factor this climate-accelerated growth into their rat management planning.”
Identifying long-term trends in rat numbers, and how they are shaped by environmental changes, is critical for understanding their ecology and for projecting future vulnerabilities and mitigation needs. In terms of possible solutions, the study makes clear that cities need to:
- Invest more resources (budget and staff) to the problem.
- Develop proactive rodent management plans that prioritize making the urban environment less conducive for rats (e.g. removing access to food waste, and
- Start collecting systematic data on rat activity and abundance rather than relying on public complaint data.
“Only by confronting the environmental factors that allow rats to thrive, and by giving municipal rodent managers the resources and tools they need, can we hope to rein in our growing rat problem,” Richardson said.
###
“Urban rats are notorious invasive pests that thrive in cities by exploiting the resources
accompanying high human population density.”
