Using methodologies outlined by Plumb et al. (1999), black-tailed prairie dog populations were monitored for the 12th consecutive year on Scotts Bluff National Monument. The main colony population declined in size and density from the previous year. Density was below the 12-year average. However, population size was well above the 12-year average. The area occupied by prairie dogs on the main colony was greater than the previous year and above the 12-year average. Areas occupied by the prairie dogs north of the canal and in the Saddle Rock unit of the monument were up from the previous year. However, populations on both had declined slightly. Evidence of Sylvatic plague, a bacterium fatal to prairie dogs, was not observed in the three populations in 2006. Four burrowing owls were observed during black-tailed prairie dog surveys on the main colony.