Case in point: Native grasslands throughout the western United States are becoming the most rapidly urbanized ecosystems in the country. Black-tailed prairie dogs, an imperiled species in western states, are increasingly found in these urban grasslands. In Boulder County, Colo., for example, nearly two-thirds of all prairie dog colonies are within a half-mile of urban development.
Prairie dogs are highly susceptible to plague, a disease that has also afflicted humans for centuries. Plague outbreaks in prairie dog colonies result in the death of nearly all prairie dogs in the colony, yet little is known about the factors that influence where and when plague epidemics will strike. Because of the close proximity of prairie dog colonies to human dwellings, concern is growing that prairie dogs may be a threat to public health.
With funding from the joint National Science Foundation-National Institutes of Health Ecology of Infectious Diseases Program, biologist Sharon Collinge of the University of Colorado at Boulder used records from two decades of plague outbreaks in prairie dogs in Boulder County to evaluate the importance of landscape setting in predicting these outbreaks.
Plague epidemics in prairie dogs, she found, were related to the surrounding landscape in unexpected ways: prairie dog colonies in urban settings were no more or less likely to experience a plague outbreak than such colonies in more rural settings. Significantly, plague outbreaks tended not to occur in colonies that were surrounded by roads, streams or lakes, suggesting that these landscape features may alter the conditions necessary for plague transmission or serve as barriers to movement of the disease.