Male Dall sheep are called rams. They are distinguished by massive curling horns. The females, called ewes, have shorter, more slender, slightly curved horns. Rams resemble ewes until they are about 3 years old. After that, continued horn growth makes them easily recognizable.
Horns grow steadily during spring, summer, and early fall.
In late fall or winter horn growth slows and eventually ceases. This is probably a result of changes in body chemistry during the rut, or breeding season. These annual rings can be distinguished from the other rough corrugations on the sheep s horns, and age can be accurately determined by counting the annuli. Dall rams as old as 16 years have been killed by hunters, and ewes have been known to reach the age of 19 years. As rams mature, their horns form a circle when seen from the side.