Fig. 3. Positive association between warming temperatures and rat numbers.

Increasing trends in rat numbers are associated with the mean temperature increase experienced in each city, above long-term baseline mean temperatures (r² = 0.478, P = 0.003). Each data point represents one city, and the size of each point corresponds to the human population density within that city, which was also associated with the trend in rat numbers (r² = 0.29, P = 0.031).