Natural Wonders

Rocky Mountain Bighorn Sheep: 

Crown Prince of the High Country

by Mike Roberts, Contributing Columnist

 

Years ago I asked my good friend and mentor, Leonard Lee Rue III (America’s most published wildlife photographer), about his favorite animal to photograph. Knowing he had spent much of his life observing, photographing, and writing about white-tailed deer, I was somewhat surprised when he ranked wild sheep at the top of the list. Nevertheless, the reply was understandable; to witness these animals in the wilderness environs where they go about their daily routines exemplifies the pinnacle of wildlife watching.

In North America, there are two recognized species of wild sheep — the bighorn (Ovis canadensis) and Dall (Ovis dalli). The thin-horned Dall sheep ranges through the mountains of northwestern British Columbia, the Yukon , the western portion of the Northwest Territories, and Alaska. In the northern sector of their range, Dall sheep are entirely white, with the coats of the mature rams sometimes having a yellowish cast. Those in the southern region are called Stone sheep and vary in color from almost black to charcoal and light gray. In areas where the two overlap, they are known as Fannin sheep.

The bighorn sheep’s original geographical distribution was extensive, spanning throughout the mountains and intermountain desert regions of western North America . When the Spanish first explored the American Southwest, they reported abundant populations of these sheep, noting in particular their large, curled horns. In 1805, President Thomas Jefferson’s famed Corps of Discovery expedition team collected bighorn sheep along the upper Missouri River. William Clark, who shot the first ram, recorded the animal’s description in detail. With the historical exploration and exploitation of the American West, bighorn numbers plummeted. Over-hunting, grazing competition from domestic livestock and the introduction of various livestock diseases were the primary factors in the rapid decline.

WHAT REMAINS

Today, three of the four recognized subspecies of bighorn sheep (the Rocky Mountain, California, and Desert) inhabit areas least disturbed by humans. The fourth, the Audubon’s subspecies, which ranged across western North Dakota, South Dakota, Nebraska, eastern Montana and Wyoming, is extinct. Sparse populations of the Rocky Mountain bighorn are distributed through the mountainous landscapes of southern British Columbia, southwestern Alberta, and southward through the Lower 48 in the rugged mountains of Idaho, Montana, Wyoming, and Colorado. In addition, various western state fish-and-game agencies have reintroduced, and in some cases introduced, the Rocky Mountain bighorn to appropriate habitat. The California subspecies, though limited in number, ranges from southern British Columbia southward through California and Nevada. The majority of desert bighorns reside in the arid, desolate areas of Arizona, California, Nevada, New Mexico, Utah, and Mexico .

As the majestic “King of the Crags,” the Rocky Mountain bighorn ram averages almost 31⁄2 feet at the shoulder and weighs between 250 and 300 pounds. Typical of hoofed mammals, the females, called ewes, are smaller in stature. The chocolate-colored coat, highlighted with white eye-patches, muzzle, underbelly, leg stripes, and rump patch, is effective camouflage for an animal that spends much of its time in rocky habitat. The desert bighorn is somewhat smaller and lighter in color. 

Both sexes have true horns that grow as long as the animal lives, which can be upwards of 14 or 15 years. The rams have massive, sweeping horns that, at maturity, can exceed 45 inches in length. Highly visible, annual growth rings are accurate indicators of an individual sheep’s age. To preserve their precious peripheral vision, mature rams often broom the tips of the continuous-growing horns, using rocks to splinter off the keratinous ends. Horn size is a key element in determining the pecking order within the summertime bachelor groups. Less imposing, the ewe’s thin, slightly curved horns are usually between 8 and 10 inches in length.

The hooves of bighorn sheep have hard outer edges and soft, cushioned centers that provide adequate traction for negotiating travel up and down sheer rock cliffs. This adaptation provides an effective means of escaping predators such as cougars, wolves, and grizzly bears. Lambs are occasionally preyed upon by golden eagles. Still, it is likely that far more bighorns succumb to disease, parasites, and falls than predation.   

Although gregarious, bighorn sheep split into two separate factions during the spring, summer, and early fall. Mature rams band together to establish rankings in the hierarchy for the late-autumn breeding season. As the last snow melts from the high country, these monarchs move up the mountains to alpine pastures where they feed on highly nutritious plants. Being ruminants, the sheep regularly bed down during daylight hours to chew their cud. Unlike most members of the bovid family, which tend to sleep in a different location each night, bighorns are renowned for using their oval-shaped beds night after night.

Throughout the year, ewes and their offspring, plus yearlings and the 2-year-old rams, remain together. Led by a matriarchal ewe, the herd typically resides at lower altitudes. The exception is when pregnant females leave the flock for a week or so during May to seek out rock ledges that are inaccessible to most mammalian predators. There, they give birth to a single lamb. Within hours of being born, the gray, wooly youngster can traverse the perilous cliffs, though never straying far from the watchful eyes of its mother. Upon returning to the herd, the lambs engage in purposeful horseplay — running and climbing to strengthen developing muscles. Although dependent upon their mother’s rich milk, the little lambs begin nibbling plants within a few days of birth. They are weaned at approximately five or six months of age.

Autumn comes early to the high country and increasing snow depths soon push the rams back down to their traditional wintering grounds, where they join forces with the ewes and yearlings. With the seasonal reduction of daylight hours, which triggers an increased level of testosterone flowing hot through their bodies, the rams begin challenging each other for the sovereign rights to breed receptive females. Posturing, lip curling, and rolling their eyes, the contestants rise in slow motion onto their hind legs and, with a sudden burst of speed, charge head-on toward each other. The result is one of the most violent collisions in all of nature. The sharp crack of sheep horns crashing together can be heard for great distances, especially in the still, brisk mountain air. Although they are sometimes dazed and pause to shake off the effects of the sudden impact, the bighorn’s skull and thick, muscular neck are designed to absorb the majority of such shock. Although often brief, these battles can go on for hours.

JUST DO IT!

While these magnificent mammals are a delight to watch in high definition on the Discovery Channel and National Geo­graph­ic, take a summer hike up Yellowstone’s Mount Washburn or along the Highline Trail in Montana’s Glacier National Park for the wildlife experience of your life. As you sit watching or photographing a bachelor herd of full-curl rams grazing wildflowers along a grassy slope, remember, you are indeed in God’s Country. Oh, by the way, because these wild places are usually good grizzly habitat, don’t forget to carry along a can of bear spray!

Wild Bird Profile:

White Ibis (Eudocimus albus)

The genus name of the white ibis is derived from the Greek term for “famed.” In ancient times, the sacred ibis (an Old World species) frequently served a significant role in religious ceremonies — even mummified and buried in tombs with pharaohs. While the white ibis of North America ’s southern latitudes may not have been legendary among Egyptian kings, the impressive flocks descending to their nighttime roosts are certainly admired by today’s birdwatchers. 

Averaging about 25 inches in height, this snow-white wader can be distinguished from species of egrets and herons by its pink, featherless face, the long, curved, pink beak and pink legs. Black-tipped primaries and rapid wingbeats, plus alternating periods of sailing, make the white ibis easy to identify in flight; the bird also flies with its neck and legs fully extended. Another key identification feature, especially at close range, is the mysterious-looking, pale-blue eye-color. Probing the shallows and mud flats, the white curlew, as it is sometimes called, feeds primarily on crustaceans, but as an opportunistic feeder, catches frogs, fish, and aquatic insects, too.

The white ibis breeds from the coastal areas of North Carolina southward through Florida and westward along the Gulf coasts of Louisiana, Texas and Mexico, to the coasts of Baja, California. Nesting in colonies, each pair of adults constructs a flimsy platform of sticks in trees and shrubs, usually less than 15 feet above water. The female lays 3 to 4 green-white eggs, which require 3 weeks of shared incubation. The young leave the nest to walk about on tree limbs about two weeks before they learn to fly.

 

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