Abstract - Interactions Among Bison, Prairie Dogs, and Vegetation in Wind Cave National Park
Coppock, D. Layne, Detling, James K. and Dyer, Melvin I. 1980. Interactions Among Bison, Prairie Dogs, and Vegetation in Wind Cave National Park. Final report to National Park Service, Wind Cave National Park, Hot Springs, SD. 177 p.
Studies were conducted during the 1978 and 1979 growing seasons to examine how bison utilized dog towns in the mixed-grass prairie of Wind Cave National Park, South Dakota. Objectives included: (1) quatifying the effects of prairie dogs on the standing crops, composition, and forage quality of vegetation, (20 characterizing seasonal trends in bison visitation to prairie dog towns, and (30 contrasting behavior patterns of bison on and off prairie dog towns.
Prairie dogs decreased peak standing-crops of total (live plus standing dead) vegetation an average of 54% at the initially modified edges of dog towns, and an average of 62% in the older core areas of dog towns compared to adjacent, off-town prairie. Changes in the overall composition of vegetation relative to off-town prairie were only evident in the core areas of dog towns, however, where the biomass ratios of graminoids: forbs were greatly decreased. Increasing duration of prairie dog impact progressively reduced the litter (mulch) layer and progressively increased the proportion of total live vegetation (relative to standing dead) in the community compared to off-town prairie. This latter trend contributed to dog towns generally having a much greener appearance than off-town grassland, particularly evident at dog town edges. Plants collected from the core areas and edges of dog towns had consistently higher concentrations of crude protein (increases over 20%) and had higher percent values for in vitro digestibility (+10%) compared to conspecifics collected from adjacent, off-town sites.
Prairie dog towns were visited by bison throughout the growing season, and during the summer dog towns ranked as one of the most-utilized habitats by bison on a Park-wide basis. Compared to bison observed on off-town prairie, bison occupying the denuded core areas of dog towns engaged in significantly more breeding-related (p < 0.5) and resting (p < 0.08) activities, while grazing was clearly reduced (p < 0.05). Bison exerted the greatest selection for moderately impacted sites near dog town margins, however, where the grazing intensity of bison exceeded estimates for animals on off-town (p < 0.04) or colony core sites (p < 0.01). Wer concluded that long-term impacts of prairie dogs in centers of dog towns encouraged rutting and resting activity in bison, while short-term impacts at dog town margins encouraged bison grazing. The reductions in obstructive, standing-dead vegetation and the increased forage quality at dog town edges may have been important factors that attracted bison to feed in these areas.
Although this report documents some of the postitive aspects of prairie dog impact in relation to bison utilization, there were no conclusions that should preclude the implementation of a wise management plan for prairie dogs in the Park. Theoretical and management implications of the bison-prairie dog interaction are discussed, and recommendations for further research are presented.