Sierra Nevada Bighorn Sheep Facts | Yosemite Wildlife Guide
When Yosemite National Park was created, hunting was allowed within the park boundaries, and all Sierra Nevada bighorns that lived in the park were killed in the first 25 years of the park’s existence.
After decades of absence, the first effort to re-introduce bighorns to Yosemite National Park happened in 1986 when 27 were translocated from other parts of the Sierra Nevada mountains. This small herd was decimated by mountain lions and severe winters.
By 1995, the entire Sierra Nevada bighorn population was estimated to be no more than 125 individuals. This led to them being listed as endangered under the Endangered Species Act, and the California Department of Fish and Wildlife was tasked with developing a recovery plan.
As part of this plan, in 2015, 13 sheep were translocated into the Cathedral Range in Yosemite National Park — an area that hadn’t seen Sierra Nevada bighorns for over a century. Their numbers were augmented with another translocation of five additional rams in 2016 and two more in 2017.
Today, there are dozens of bighorns making up three herds in the Cathedral Range, which are part of an overall population that has grown to over 600 throughout the Sierra Nevada range.
PHYSICAL CHARACTERISTICSThe bighorn sheep’s fur is tan or brown in color, and it has a white belly, rump and muzzle. The ram’s large horns can weigh 30 or 40 pounds, representing over 10% of total body weight. The ewe’s, or female’s, horns are more slender and less curved. Males weigh between 125 and 220 pounds; the females of this species are smaller, weighing up to 155 pounds. The bighorn is a good climber and jumper. Its hooves are hard around the outside and soft on the inside, which help give them traction on slippery rocks.
Their horns are less massive and curled than the weapons found on desert bighorns.
BEHAVIOR & BREEDINGIn the fall, males have head butting contests to establish dominance; however, rams usually only fight with other males that have similar-sized horns. They run at each other at speeds of up to 20 miles-per-hour and ram their heads together. Amazingly, head butting contests have been known to last as long as 20 hours! The dominant ram will mate with more females than the other rams. When a male is ready to mate, he will go into a herd of females. The female will chase the male before they mate, and sometimes, a male will kick a female to get her to chase him.
Females typically give birth to their single offspring on a cliff that is difficult to access. Lambs are born woolly and white with little horns. The lamb will stay hidden where it was born for about a week, and then it will start to follow its mother. Male lambs will leave their mother and join a male group when they are between two and four years old. Female lambs will usually remain with their mother’s group for their entire lives.