Pronghorn antelope at Hart Mountain National Antelope Refuge have been in decline since the early 1990s. These antelope have been shown to be selenium and copper deficient. These deficiencies have marked wildlife declines for the last 30 years across the West, and have been seen in black tailed deer in California, Moose in Utah and Minnesota, antelope in Idaho and Arizona, bighorn sheep in Wyoming, and elk in Washington.
In the Early ’90s a new management plan was put in place at Hart Mountain, that consisted of extensive habitat rehabilitation, after cattle grazing was banned from the refuge. As much as 20% of the refuge was burned, and herbicides were used for weed control. By all accounts the habitat has come back, and appears to be doing well. Yet the antelope have not rebounded, nor have mule deer, bighorn sheep, or sage grouse. As recently as 2011, an expansion of herbicide use at Hart mountain and Sheldon Antelope refuges has been sought.