Unique Aspects of the Ecology of Bighorn Sheep Occupying a Clay Hills-Prairie Environment in Badlands National Park

Moses, Michael; Bessken, Bruce; Gamo, R; Cordts, Steve; Singer, Francis

"Bighorn sheep (Ovis canadensis) numbers throughout western North America declined dramatically during the late 1800's and early 1900's (Seton 1927,Cowan 1940). Nearly a century after experiencing catastrophic losses, many bighorn populations have yet to recover to historical levels (Hoefs, 1984). Restoration and maintenance of viable populations is the primary goal of bighorn sheep management. This paper investigates the incidence of lungworm disease; effects of fire on forage quality; dietary content; and habitat selection by bighorn sheep that occupy a clay hills-prairie environment in BADL, South Dakota. Bighorn sheep herds in the North and South Units of BADL differ in their founding history, total population and population density. The incidence of lungworm larvae in bighorn sheep fecal samples were higher in the North Unit. Infestation levels were unrelated to variation in yearly rainfall totals. For five forage plant species, only minor changes in dry weight, percent nitrogen, percent protein, and dry matter digestibility were detected in the two years following seasonal burn treatments. Microhistological analysis of fecal samples indicated the Agropyron spp. were the dominant forage in the North Unit and Stipa spp. were dominant in the South Unit. Seasonal habitat use data showed that ewe groups were most often observed on elevated sod buttes during the winter and spring; on shadier midslopes and ridges during the summer; on or near the steepest escape terrain during lambing; and farthest from escape terrain during the rut." (from document Abstract)