Analysis of Bighorn Sheep Survival Data

Park managers and researchers have recently analyzed bighorn sheep survival data and the initial effects of wolves (Canis lupus) on population dynamics of sheep in Yellowstone National Park. Analysis of survival estimates indicated that the population was increasing or constant and that the presence of wolves did not prevent the sheep population from increasing slowly since reintroduction in 1995. Though recruitment increased and the sheep population increased 7% annually during 1998–2005, the population remains low since the keratoconjunctivitis outbreak in 1981–1982, which suggests other factors are limiting recovery. Elk (Cervus elaphus) potentially compete intraspecifically with sheep, and the elk population decreased by 50% during 1998–2005 while the sheep population increased. Conclusions from this analysis suggest the need for an examination of the potential effects of decreased competition with elk on lamb recruitment and sheep population growth.