I saw my first ever Rocky Mountain Bighorn Sheep on Thanksgiving Day 2013. I heard that they had started to migrate to “lower” elevations  in the late autumn where there is more food available for them (“lower” meaning ~6,000 ft as opposed to ~10,000 ft– 6,000 ft being higher than the highest point in Maine makes it hard for me to apply the word “low” anywhere near a description of that elevation). While attempting to fish on the Gros Ventre River but quickly discovering even the swiftest parts were frozen solid, Joe and I decided to look for the elusive Bighorn Sheep we’d heard rumors of in the area. At the ridge of a nearby hillside, we saw the telltale silhouette of two pairs of curved horns. We quietly walked up a nearby hillside to get a better look while still keeping our distance and discovered a much closer lone ram laying down nearby, chewing his cud.

That was the first of many sightings we’ve had of these wild sheep since. On the National Elk Refuge Road in Jackson, they frequently cover the roads licking up salts and other minerals left behind, which is where I took most of the above photos.

Natural History Nuggets: Yet another creature that used to be far more common than they are now, Bighorn Sheep used to cover western North America but today have patchy populations throughout that range. They were nearly extinct by the early 1900’s, but conservation efforts promoted their return. Their population declined again in the 1980’s due to an outbreak of conjunctivitis. Yes that’s right; many of these sheep died because their bout with pink-eye nearly blinded them and caused many to fall off the cliff-sides they frequent.

There are two or three subspecies of Bighorn Sheep in North America: Rocky Mountain Bighorn Sheep, Ovis canadensis ssp. canadensis, Desert Bighorn Sheep, Ovis canadensis ssp. nelsoni, and a third less mentioned possible subspecies, the Sierra Nevadan Bighorn Sheep. Desert Bighorn live in the southwestern US and northern Mexico whereas Rocky Mountain Bighorns span the range of the Rockies from Canada to Mexico. I bet you can guess where the Sierra Nevadan ones live.

They have keratin-composed horns that do not shed (as opposed to calcified antlers which do shed annually), which can weigh up to 40 pounds. During the rut, when rams are trying to impress the ewes for mating, powerful head butting between males can echo throughout the area. Check out this National Geographic video of Bighorn Sheep during the rut. Their skulls are specially adapted not to crush during such head butting events due to honeycomb-like air pockets located throughout the thick bone of the skull. The small size of their brains does not require much space within the skull, so having a thicker skull is more advantageous. Apparently some helmet-makers are using the design of bighorn sheep skulls for engineering more effective helmets.

Ever seen a ram near a ewe with his chin up, upper lip curled, and mouth slightly ajar displaying the most raunchy facial expression you have ever witnessed? Bighorn Sheep (and many other mammals, surprisingly) have an area on the roofs of their mouths called the Jacobson’s Gland which allows them to better smell whether the ewes are in estrus.

And why do these sheep have such a penchant for cliffs? As one can imagine, these sheep would be a relatively easy target for predators even with their impressive horns. By standing on the edges of cliffs, few predators are willing to take the risk to approach them for fear of falling off the cliffs themselves. Pretty neat!

References:

http://www.bighorn.org/biology.html

http://www.nwf.org/wildlife/wildlife-library/mammals/bighorn-sheep.aspx

http://www.nps.gov/yell/naturescience/bighorn.htm

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