By R.J. Mackie, R.F. Batchelor, M.E. Majerus, J.P. Weigand, and V.P. Sundberg
Pronghorn Habitat Requirements
Optimum pronghorn habitat is characterized by the presence of big sagebrush and/or silver sagebrush in combination with rabbitbrush and the general environmental factors associated with these plant communities.
Even though pronghorns generally occupy grassland ranges, their diet consists of essentially browse and forbs. Diet samples from 900 animals in seven states averaged 64 percent browse, of which 75 percent was sagebrush. The degree of browse is of critical importance for pronghorn survival during the fall and winter months on their northern ranges, particularly when snow covers all other feed. The major browse species utilized are Wyoming big sagebrush, silver sagebrush, Douglas rabbitbrush, rubber rabbitbrush, and western snowberry.
Forbs appear to be of critical importance for pronghorn survival on more southerly ranges. Depending on their season of availability, forbs make it possible for pronghorns to be less dependent on what may be very limited free water supplies. An extended greening-up period, coupled with great species variety, make forbs a very important summer and early fall food and water source. In some drier areas, during some summers, forb use amounts to as much as 93 percent of the pronghorns' diet. Biscuitroot, knotweed, white and yellow sweetclover, alfalfa, lupine, prairie clover, vetch, buckwheat, and rockcress are only a few of the preferred forbs.
Year-round, grasses are of minor importance in the food habits of pronghorns, averaging less than 10 percent of their diet. In early spring and fall, when it is the only green succulent forage available, consumption of grasses might be as much as 32 percent of the diet. Some of the major grasses utilized include western wheatgrass, needle-and-thread, Sandberg bluegrass, sand dropseed, and basin wildrye.
Habitat Management Suggestions
With respect to antelope habitat, more fruitful accomplishments are likely to be achieved through maintenance of existing habitat than through efforts attempting to restore antelope habitat where it has been degraded.
In range improvement programs that involve brush management, sagebrush should not be treated until a conservation plan has been formulated that includes the needs of wildlife. Livestock allotments that occupy antelope range need to be properly managed to ensure sufficient vegetative cover for antelope. Proper grazing of forbs and grasses by grazing animals will not damage antelope habitat.
Brush management programs should not be undertaken when sagebrush crown canopy cover does not exceed 20 percent or on steep slopes with skeletal soils. Sagebrush of this density or less is generally considered to be acceptable in its competition with desirable range grasses. Improvement of such grass stands through control of sagebrush would not likely be economical, even with a complete kill of sagebrush, if the only product is livestock forage. Greatest improvement in range condition of such areas is most likely to result through proper livestock management.
Where sagebrush management is judged necessary, control should be applied in irregular patterns wherever possible, using topographic features, soils, density of sagebrush and habitat requirements of sage grouse, mule deer, pronghorn, and other native wildlife as pattern-determining considerations.