Dall Sheep

(Ovis dalli)

I photographed this mother Dall Sheep and her lamb in the high mountains of Denali National Park, Alaska. The females (known as a “ewe”, pronounced like “you”) give birth in late May or early June, which makes this lamb less than a month old! Ewes give birth to a single lamb each year and remain in the “lambing cliffs” for several days until the lamb is old enough to walk and feed on its own.

They are also known as Thinhorn Sheep because their horns are slightly thinner than their southern counterpart, the Bighorn Sheep, which is found throughout the American Rockies down to Mexico. The ewe’s horns, as seen in the photo above, are smaller and only slightly curved. The ram’s horns get much larger and eventually curl into a full circle. Horn growth slows down each year during the rut (mating season) which causes rings to form as they grow (known as “annuli”). This means that a Dall Sheep’s age can be accurately determined by counting the annuli, kind of like counting growth rings on a tree! Rams use these massive horns to crash into each other at high speed. This ritual determines breeding dominance between males.