Figure 1.

Prairie dogs (left) are burrowing, herbivorous, diurnal ground squirrels that inhabit the grasslands and shrublands of the Great Plains of North America (photograph: Austin Allison, Colorado Parks and Wildlife). The most widespread of the five species, the black-tailed prairie dog (Cynomys ludovicianus) is the most social and highly susceptible to plague mortality (Cully and Williams 2001). In suitable habitat, black-tailed prairie dogs can occupy large (hundreds of hectares), densely populated colonies. Within a colony, prairie dogs live in territorially defended social groups called coteries, consisting of 1–2 adult males, 2–4 adult females, yearlings, and juvenile offspring (Hoogland 1995). Prairie dogs are commonly infested with fleas: 88% of prairie dogs in Colorado had fleas, with an average of 14.3 fleas per infested host (Tripp et al. 2009). The vast majority of fleas were one of three species: Oropsylla hirsuta (right, photograph: Dan Tripp, Colorado Parks and Wildlife), O. tuberculata cynomuris, and Pulex simulans. Except for P. simulans, which is also found on carnivores, the fleas associated with prairie dogs are rarely found on other mammals (Brinkerhoff et al. 2006, McGee et al. 2006, Salkeld et al. 2007, Stapp et al. 2009, Tripp et al. 2009).