Figure 2.

A conceptual representation of the anatomy of a plague outbreak in a prairie dog colony. Field observations show that plague activity may be ongoing several months prior to a recognized prairie dog die-off (St. Romain et al. 2013). High grasshopper mouse abundance is correlated with a higher likelihood of plague outbreak the following year, although grasshopper-mice populations are also affected by Y. pestis activity (Stapp et al. 2008, 2009). The abundance of fleas infected with Y. pestis also rises during the observed outbreaks (Tripp et al. 2009).