Comparative Study of the Spatial Organization and Zoogeomorphic Effects of Black-tailed Prairie Dogs
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Site specific burrow densities of black-tailed prairie dog towns were estimated via point counting on aerial imagery for the following three sites managed by the National Park Service (NPS): Devil’s Tower National Monument (DTNM), Theodore Roosevelt National Park (TRNP), and Wind Cave National Park (WCNP). These average burrow densities were 14, 7, and 5 burrows per 30 m2 respectively. The burrow densities in conjunction with burrow dimensions from Sheets et al. 1971 were used to quantify the volume of sediment excavated by black-tailed prairie dogs. Observations reveal that WCNP contained the largest, most stable towns. Consequently, WCNP had the largest volume of excavated sediment, which was 163,379.68 m3. TRNP contained the greatest number of towns and an average burrow density greater than WCNP. Town size and percentage within TRNP resulted in excavated sediment estimates approximately half the volume of the WCNP estimates. Estimates of excavated sediment within DTNM were limited by park size and town percentage. Slight variations in habitat characteristics, epizootic disease history, and management objectives within WCNP provided the most favorable conditions for prairie dog town persistence.
As compared to excavated sediment estimates by Butler 2006, the estimates of this study are up to five times larger. Excavated sediment estimates are influenced by burrow density. Discrepancies in burrow density may be potentially caused by differences in town area calculations, changes in town growth and population stability, and/or an overestimate of burrow density because of the methodology or data used in this study. Based on the historic records of town area in Wind Cave National Park, it was found that town area calculations of this study were concurrent with town growth projections of Dalsted et al. 1981. For this reason, town area calculations are believed to be sound. Discrepancies in burrow density are likely attributed to mistaken counts of inactive prairie dog burrows, natural increases in burrow density via town growth and stability associated with improved management techniques, and/or the use of aerial imagery and observation extents which were poorly suited for differentiation between burrows and bare ground.
Although there are discrepancies in burrow density estimates and consequently sediment estimates, the implementation of different techniques and lessons learned from this project can only move the field of zoogeomorphology forward. Temporal information regarding burrow longevity and excavation rates can be used with estimates of excavated sediment to quantify the zoogeomorphic effects of black-tailed prairie dogs in past and present environments. Management of keystone species within the Great Plains will be more comprehensive as we better define the role of black-tailed prairie dogs in grassland habitat.