Despite the broad and relatively stable distribution of the black-tailed prairie dog (Cynomys ludovicianus) throughout much of the Pleistocene and Holocene, anthropogenic activities have reduced the current range of this native grassland species and its associated biotic community to Ͻ5% of its historic range (approximately 1800 -Miller et al. 1990 , 1994 . We studied the biogeography of the black-tailed prairie dog along the southeastern edge of its geographic range with 3 primary objectives:

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... o assess the status of the species in this region and identify trends in town coverage and mean town size over the past century, to test whether town persistence was associated with area and isolation of towns, and to assess the protection status of towns Ͼ10 ha by comparing locations of extant towns to those of protected public lands. Prairie dog towns in this region now represent only 1% of presettlement estimates and continue to decline in total acreage because of advanced agricultural practices, systematic control measures, and outbreaks of plague. Further, Ͻ1% of the area now occupied by prairie dog towns Ͼ10 ha occurs within protected locations. As the total coverage of towns has declined, mean size of towns has decreased, and towns have become increasingly more isolated. Persistence of towns between 1989 and 1997 was highest for the largest and most isolated towns, even in regions that were not known to be influenced by plague.