One of the most sure-footed animals in Yellowstone is the big horn sheep. They’re known for the massive curled horns on either side of the ram’s head. But don’t expect all of them to sport large coiled horns. Only the rams or adult males have full curls, while ewes and lambs have much shorter spikes.
The horns are made of keratin (like hair and fingernails) and form over a small extension of bone from the skull. The outer ends of horns are hollow and if the tips break or splinter they won’t grow back. The horns grow from the base getting larger and curling more each year.
Annual growth rings in the horns can help you determine the age of the sheep. As a ram gets older his horns may curve in a spiral all the way back around beside his eyes. He may have to scrape them against something to wear them down so he doesn’t lose peripheral vision.
Rams use their horns to gain dominance within a herd and access to females. The rut is in November when rams may challenge each other by running at each other and then rising on their hind legs just before they butt heads and ram their horns.
These stout males can weigh about 300 lbs with 20 to 40 pounds in their horns. Eventually one ram runs away or acts subordinate and the challenge ends. These jousts for dominance mean the larger, stronger males get to mate.
Ewes have one or two lambs in May or June and the lambs climb almost as well as their mothers within a day or so of birth.
Big horn sheep have concave feet which allow them to run and leap around on steep and rocky slopes. There they’re safe from most predators and can forage with little competition for forbs and grasses. They browse more shrubby plants in the winter and their underhair of angora keeps them well-insulated in wind and snow.
Perhaps their tendency to rely on vision more than their sense of smell or hearing led to a reduction in big horn sheep numbers in the early 1980s. The population is still slowly recovering from a pinkeye epidemic that wiped out 60% of the population.
Count yourself lucky if you see big horn sheep in Yellowstone as there are only about 250 in the park and they inhabit rugged, high, rocky terrain. Your best chances at spotting them are along the slopes of Mt. Washburn where some migrate in the summer, and in the Gardner River Canyon and Mt. Everts, across the Yellowstone River from Calcite Springs, and above Soda Butte.
Look closely since their tan fur blends in well with the rocky cliffs. Don’t feed them even if they venture down to the roadways. This makes them more prone to getting hit by cars. Keep them wild, healthy and majestic.