Dall Sheep

Horn growth on Dall's sheep rams becomes visible when the young males are around three years old.

NPS Photo

 

Dall sheep are the northernmost species of wild sheep in North America. In Alaska, Lake Clark is the furthest southwest extent of their range. These pure white sheep love their mountains. They ramble along rocky ridges and sleep on steep slopes. Though there are many mountains in the park, Dall sheep live on few of them. If the peaks are too high, vegetation is too scarce. Too close to the coast and long winters can bury food beneath a heavy blanket of snow. In Lake Clark ideal habitat exists on the western slopes of the Chigmit Mountains along the boundary of the park and preserve. Look for them tiptoeing on Tanalian Mountain or prancing along the peaks near Twin Lakes.

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. Annual aerial counts show the population is holding steady at around 1,000 sheep 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 in that 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.