Mountain Monarchs

Article excerpt

Dwight G. Smith is professor and chairman of the Biology Department at Southern Connecticut State University in New Haven.

North America's wild sheep have conquered some of the most remote and inhospitable terrain, but the stability of their populations remains uncertain.

Old Man created the mountains and prairies and all the animals and plants. Finding the bighorn too slow and awkward for life on the prairie, he took it up into the mountains, where it skipped among the rocks and bounded up fearful places with ease. "This is the place that suits you best," Old Man said, and bighorns have remained in the mountains ever since.

--Blackfoot Legend

It was the middle of January, and the temperatures were freezing. I was right at the bottom of the Grand Canyon, walking along a shelf of land no more than 15 feet wide. On my left, the icy Colorado River hissed past me, while the sheer canyon walls rose 2,000 feet vertically on each side, nearly shutting out the pale winter sky. In my mind, this was surely the most inhospitable place on earth. After all, what in the world could survive amid this harsh landscape?

As part of a survey team, I was exploring the canyon for winter wildlife. Suddenly, my eye was attracted to a set of tracks in the sand. They revealed that a bighorn sheep had come by earlier, pausing to drink from the river. As I straightened up to look for the animal, I recalled the Blackfoot legend--surely only a bighorn could clamber up and down these fearful heights that walled me in so completely.

The bighorn's ability to navigate safely among precipitous cliffs is legendary. It has been observed to jump 20-foot chasms with ease, scale steep slopes at 20-30 miles an hour, and follow trails scarcely more than a couple of inches wide. I once watched a small band of rams climbing a steep, ladderlike formation in a cleft in the Marble Canyon in Arizona. Entering the base of the cleft in single file, they swiftly ascended the cliff by leaping from side to side, emerging at the top, 100 feet above me.

Meet the sheep

The tracks I had observed in the Grand Canyon belonged to the Rocky Mountain bighorn, so named because it dwells in the Rockies, from southern Canada to Colorado. It has a brown coat that fades in the winter, while its muzzle and rump are often white. A related population, commonly referred to as desert bighorn, is adapted to the dry, cacti- covered hills of southwestern United States and Mexico.

The scientific name for bighorn sheep is Ovis canadensis. This species has been traditionally divided into seven subspecies, including Rocky Mountain bighorn (O. c. canadensis); Nelson's bighorn (O. c. nelsoni), the most common type of desert bighorn; and California bighorn (O. c. californiana), occurring from British Columbia south to California and eastward to North Dakota.

This subdivision of the species has been challenged by some researchers who, based on DNA studies, have suggested that there are only two subspecies: O. c. nelsoni, the more widespread form that includes desert bighorns in parts of Arizona, Nevada, and Baja California; and O. c. californiana, a small population in the Sierra Nevada. There is, however, still some debate about the new classification system.

Thinhorn sheep (Ovis dalli) form a separate species of mountain-dwelling sheep in North America. One subspecies, Dall's sheep (O. d. dalli), is pure white and considered by many to be the most beautiful of wild sheep in the world. It makes its home amid the alpine scenery of Alaska and much of western Canada, living chiefly above the timberline. A second subspecies, Stone's sheep (O. d. stonei), is found mainly in British Columbia and varies in coloration from light gray to black.

Like other sheep, O. canadensis and O. dalli are part of the family Bovidae, which includes goats, antelope, and cattle. This family is placed within the great order of even-toed mammals known as artiodactyls. …