Influence of fire on black-tailed prairie dog colony expansion in shortgrass steppe

Factors influencing the distribution and abundance of black-tailed prairie dog (Cynomys ludovicianus) colonies are of interest to rangeland managers because of the significant influence prairie dogs can exert on both livestock and biodiversity. We examined the influence of 4 prescribed burns and one wildfire on the rate and direction of prairie dog colony expansion in shortgrass steppe of southeastern Colorado. Our study was conducted during 2 years with below-average precipitation, when prairie dog colonies were expanding throughout the study area. Under these dry conditions, the rate of black-tailed prairie dog colony expansion into burned grassland ((X) over bar = 2.6 ha . 100-m perimeter(-1) . y(-1); range = 0.8-5.9 ha . 100-m perimeter(-1). y(-1); N = 5 colonies) was marginally greater than the expansion rate into unburned grassland ((X) over bar = 1.3 ha . 100-m perimeter(-1) y(-1); range = 0.2-4.9 ha . 100-m perimeter(-1) . y(-1); N = 23 colonies; P = 0.066). For 3 colonies that were burned on only a portion of their perimeter, we documented consistently high rates of expansion into the adjacent burned grassland (38%-42% of available burned habitat colonized) but variable expansion rates into the adjacent unburned grassland (2%-39% of available unburned habitat colonized). While our results provide evidence that burning can increase colony expansion rate even under conditions of low vegetative structure, this effect was minor at the scale of the overall colony complex because some unburned colonies were also able to expand at high rates. This result highlights the need to evaluate effects of fire on colony expansion during above-average rainfall years, when expansion into unburned grassland may be considerably lower.