Rocky Mountain Bighorn Sheep
It never fails when people see bighorn sheep; they are fascinated, be it the horns on the rams, the ewes, and lambs, or a lamb jumping over the rocks of their home. Rocky Mountain Bighorn sheep are found in the Rockies of North America from British Columbia to Arizona. Except during mating season, you will find the rams or males in small groups and the ewes, females, and lambs in separate groups. Rams can weigh up to 319 pounds (144.7 kg), while females are about half that weight. |
![]() A small herd of ewes and young lambs along the Gardiner River in Yellowstone National Park. |
![]() A young lamb by mother who is still dressed in winter wool. |
Ewes can produce lambs between 2 and 16 years of age. Mating begins in November. Gestation is 6 months, and usually has one lamb yearly. Yellowstone lambs are born in May or June. Before giving birth, the ewe will find a remote area and will stay there until the lamb is several days old. At that point, they rejoin the herd. In just days, the newborn is jumping over rocks and climbing the side of mountains Lambs are weened by four to six months. The ram lambs stay with the ewes until two to four years of age. Female lambs stay with their herd for life. |
When looking at adult rams, the most impressive thing you see is their C-curved horns. Being horns, they are never shed by the ram. The horns continue to grow from the head outward. If a tip gets damaged in a horn-bashing clash, the tip never "heals." A damaged horn is said to be "broomed." The bigger the C-curve, the older the ram. The horns on an adult male can be 8-12% of his total body weight. 25.5 or 41.5 pounds (11.6 - 18.8 kg). A complete set of horns takes 7-8 years to grow. Females grow horns, but the horns are more petite and slender, never form a "C," and stop growing at about age 4 or 5. Until three years of age, the young ram looks like an ewe; after that, his horns start to develop the recognizable "C" shape. |
![]() A closer look at a ram's "C" curved horn. |
Rocky Mountain Bighorn Sheep is one of Yellowstone's seven native ungulates or hooved animals.
The most recent count of the Bighorn in Yellowstone was reported in 2018. At that time, 345 sheep were found in the Greater Yellowstone northern area, with 131 animals within the park's defined boundaries. The average life span for males is 9-12 years, and females are 10-14 years.
The average life span for males is 9-12 years and females are 10-14 years.
What is the difference between horns and antlers? To find out, check out this page.
![Bighorn ewe with twins](../Site/images/wildlife/bighornewewithtwins.jpg)
Bighorn ewes typically have single births, but twin births occur. This family came up behind my brother and me while photographing something in the Yellowstone Grand Canyon near Tower Junction. They came around us and went along the canyon's edge to wherever they were going. Mama is shedding her winter coat. On the other hand, we stood there in awe with our fingers working our camera shutters. What an experience.