National Park Service


Date of this Version



Published in PRAIRIE INVADERS: PROCEEDINGS OF THE 20TH NORTH AMERICAN PRAIRIE CONFERENCE, UNIVERSITY OF NEBRASKA AT KEARNEY, July 23–26, 2006, edited by Joseph T. Springer and Elaine C. Springer. Kearney, Nebraska : University of Nebraska at Kearney, 2006. Pages 349-358.


The black-tailed prairie dog (Cynomys ludovicianus), a keystone prairie species, historically occupied over 404,700 ha (100 million ac) of short- and mixed-grass prairie. Today, they occupy less than 2% of their original range. Scotts Bluff National Monument, Nebraska is one of eight National Park Service units with one or more black-tailed prairie dog colonies. Since 1995, a total of 202 observations were made on the population of the main colony at Scotts Bluff National Monument, to estimate annual densities and abundances. Estimated annual densities ranged between 9.2 and 53.0 individuals/ha (2.5 ac). Average density of prairies dogs was 25.1 individuals/ha (2.5 ac) annually. With the exception of 1996 and 2005 (density estimates 53.0 and 44.9 individuals/ha (2.5 ac), respectively) all other densities were similar across years based on overlapping confidence intervals. The estimated prairie dog populations ranged between 17 and 802 individuals, with an annual average of 291.3 individuals. During the last 5 years of monitoring the estimated average annual population size was 527.6 individuals. Based on the lack of overlapping confidence intervals, the prairie dog population increased significantly every 3 to 4 years. Colony size ranged between 1.4 and 37.7 ha (3.5 and 93.2 ac) during our 11 years of monitoring, with an average annual colony size of 13.0 ha (32.1 ac). During the last 5 years of monitoring the average annual colony size increased by 8.5 ha (20.9 ac). Sylvatic plague was not observed in the black-tailed prairie dog colony at Scotts Bluff National Monument between 1995 and 2005, which was important to the stabilization and increase of the colony’s population. Our monitoring demonstrates that a viable black-tailed prairie dog population can establish from a few vagrant individuals and that recovery from a near 100% die-off is possible.