In 2001 the Colorado Division of Wildlife (CDOW) began writing a conservation plan for shortgrass prairie species including the black-tailed prairie dog (Cynomys ludovicianus), partly in response to a petition filed to list the black-tailed prairie dog as a Threatened Species and a finding made by the United States Fish and Wildlife Service (USFWS) that a listing was warranted but precluded. To determine the status of the species in Colorado, acreage of active black-tailed prairie dog colonies was estimated in eastern Colorado during June-August 2002, using aerial line intercept methods. We stratified the survey by county boundaries based on imperfect prior knowledge of colony areas by county and computed the proportion of each line intersecting active prairie dog colonies. Active colonies were defined as colonies with prairie dogs observed from the air or fresh digging at burrow entrances. For 131,615 km2 surveyed, estimated area of active colonies was 255,398 ha, with a 95% confidence interval of ±9.5%, indicating that 1.94% of the surveyed range was occupied. This estimate may be biased low because some active colonies might have been misclassified as inactive or because some active colonies might not have been spotted when flown over. In contrast, this estimate may be biased high because some active colonies included in the survey may be active in only a portion of the colony considered as intersecting the survey line. However, our estimate for Colorado was consistent with the estimated area of active black-tailed prairie dog colonies in Wyoming from Sidle et al. (2001), where 2.02% of 66,085 km2 was estimated to be occupied.
White, G.W. et al.: Area of black-tailed prairie dog colonies in eastern Colorado
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