Dall sheep are the northernmost species of wild sheep in North America. These white sheep range along the western slopes of the Chigmit Mountains along the boundary of the park and preserve. Park wildlife biologists have been studying the Dall sheep in the park for several years, including a GPS radio-collar population and distribution study completed in 2008. During the two year study, radio collars collected over 40,000 GPS locations of the 40 sheep collared. Locations were then used to determine home range, seasonal movements and habitat use for sheep in Lake Clark. An aerial survey was conducted in July 2012 for all suitable sheep habitat within the park and preserve.
Male dall sheep are called rams and are distinguished from the females (ewes) by their massive curling horns. Horns are different from antlers because horns are a slow-growing, permanent bone, covered by a thin sheath of hard, bony keratin. The entire horn is never shed or "dropped" like antlers. Ram horns grow continually in a spiral, but growth slows down during winter. The annual decrease of horn growth results in a pattern of rings along the horn called annual rings. A sheep's age can be determined by counting these rings. Ewes have horns that are shorter, blunter, and grow in a gentle arc over the head. They also have annual rings. Rams frequently use their horns to fight during the mating season.
The adult rams live in groups apart from the ewes except during the late fall mating season. The young are called lambs and are born in late May or early June. In anticipation of lambing, ewes seek protection from predators in rugged cliffs and will remain there a few days until the newborn lambs are ready to travel.
Like many animals in Alaska, Dall sheep eat a wide variety of plants during the summer, when food is abundant. Winter diets are more limited and can include dry, frozen grasses, sedges, lichens and moss. Dall sheep often travel great distances to visit mineral licks in the spring. They eat the soil at these typically rocky outcrops where high concentrations of minerals are pooled. This replenishes essential minerals that the sheep cannot get from their daily diet of plants.