- There are four subspecies of North American wild sheep: Thinhorns which consist of the Dall's and Stone's sheep; and Bighorns which consist of the desert and Rocky Mountain bighorn sheep. - More than 90 percent of North American wild sheep reside on public lands. - State, federal, crown land agencies as well as tribal entities play an important role in wild sheep management. - Disease transmitted from domestic sheep to wild sheep is the No. 1 limiting factor to successful recovery of wild sheep populations. - Some public lands allow domestic sheep grazing in suitable historic wild sheep habitat causing large scale die-offs with many years of poor wild sheep lamb recruitment.