Bob and I were well on our way back up to the South Rim from Plateau Point at Grand Canyon National Park after a grueling 12-hours of hiking, so with our noses to the grindstone, we just focused on putting one foot in front of the other to make headway. That is why neither one of us saw the Bighorn Sheep (Ovis canadensis nelsoni) surveying its surroundings from a ledge above the trail, just below Mile-and-a Half Resthouse. If not for other hikers mentioning sight of the animal, we would have completed our hike in total ignorance of its presence.
It had been a long haul from Plateau Point, scaling the steep slopes back up the canyon wall, and for the duration of the afternoon, Bob and I had been hiking in full sunshine. Our trek had begun at 5 a.m., and we were nearing the end of our energy stores.
We had actually reached the rest stop and were taking advantage of the fresh water supply when we heard animated conversation between other hikers who had seen a Bighorn Sheep just below us on the trail. Bob and I were stupefied. How could we have walked right past it and not noticed? Our exhaustion and intense focus was the only explanation for disregarding our surroundings.
I could not bring myself to hike even a short distance back down the trail as I had barely enough energy left to carry me to the top of the canyon. It was all I could do to put one step in front of the other in order to keep moving forward. So, Bob retraced his steps down the dirt path while I rested and refreshed myself. It was one photographic opportunity that he did not want to miss.
As Bob descended the switchbacks, he feared that the sheep might have moved off, but there it lay in full view some ten feet above the trail in a protected alcove shaded from the sun. Such a cliff habitat is useful as it provides protection from predation and enables a sheep to avoid competition from other herbivores, but at the same time, such steep, rugged terrain also means that Bighorn Sheep often fall to their deaths.
This male Bighorn Sheep, a ram, has an impressive pair of ridged, brown horns that curl back over the ears then down and up again towards the cheeks. By the time a ram is 7 or 8 years of age, his horns will achieve a full curl with a width of 30 inches and a weight of near 30 pounds (14 kg). Older rams will often have curling horns that are at least 3 feet long with a circumference at the base of the horn of over one foot. It is the large curved horns of the rams that inspired the name for this species of animal.
Desert Bighorn Sheep are a subspecies of the Rocky Mountain Bighorn Sheep, but both of these species are descendants of the wild sheep found in Central Asia. Their ancestors crossed to North America using the Bering Land Bridge from Mongolia and Tibet before the last ice age. Desert Bighorn Sheep are found in the deserts of Southwest United States as well as the northern areas of Mexico.
Desert Bighorn Sheep share the same characteristics and behave similarly to other species of Bighorn Sheep, but they have adapted in a unique way. They are able to survive for extended periods of time without drinking water, which is why they are able to subsist in a mountainous desert environment where there is next to no permanent water. Moisture is acquired through food sources or small pockets of rain water.
Desert Bighorn Sheep at one time numbered in the tens of thousands, a small fraction of the overall North American population which was estimated to have been between 1.5-2.0 million. Many factors are responsible for their downturn in numbers – hunting, loss of habitat, confiscation of watering areas for human use, competition with livestock, wild horses and feral burros, and diseases from domestic stock. They have little resistance to infections carried by European sheep and cattle, and, in particular, pneumonia poses a huge threat to the species.
By the 1930s, Frederick Russell Burnham established that there were fewer than 150 Desert Bighorn Sheep still living in the Arizona mountains. In 1936, he initiated a massive campaign through Arizona Boy Scouts to save the majestic animals from extinction. He was a forward thinker and thought that future generations of domestic sheep might possibly be saved from disaster by some as yet unknown virus by providing them with a strain from the wild sheep.
Other well known groups, National Wildlife Federation, Izaak Walton League and National Audubon Society, joined forces, and together, the conservation effort saw the establishment of two wildlife refuges for Bighorn Sheep: Kofa National Wildlife Refuge and Cabeza Prieta National Wildlife Refuge. Today, it is believed that between 18,965 – 19,040 Desert Bighorn Sheep live in well-established herds on about 4% of their original ranges.
As Bob observed this beautiful ram, he became quite disconcerted when the sheep began to retch and then throw up. Was the ram in distress? Was it diseased? Or was it just regurgitating partially digested food? Desert Bighorn Sheep are ruminants, which means that they can extract the maximum amount of nutrition and moisture from the foods they eat by chewing a cud of regurgitated food.
Within minutes, the sheep got to its feet and began to eat leaves from a nearby bush. As part of their diet, Bighorn Sheep browse on shrubs, graze on grasses and will even eat cacti. Ewes have horns, too, though smaller, shorter and lighter than those of rams, so both genders are able to use their horns as tools to break open cacti. Most often ewes forage while they walk as it serves to avoid predators and keep lambs safe. Rams, on the other hand, usually eat then rest and ruminate. This self-serving lifestyle leads to more effective digestion and larger body size.
Bob was amazed at the nimbleness of the ram there on the sloping ledge. Even as the scree slid out from under its feet, the sheep remained solid in its position. Each of a Bighorn Sheep’s feet has 2 hooves, which is an adaptation that is necessary for their cliff dwelling lifestyle. The sharp-edged cloven hooves are an advantage for clinging to steep cliff terrain. The hooves are also elastic and concave allowing the sheep to zigzag up and down cliff faces with amazing dexterity, sometimes using ledges as narrow as two inches for footholds.
As the ram grazed on the shrub, Bob took notice of its short, stocky, muscular body. The sheep’s short legs give the animal a low centre of gravity, and when required, it can bounce over crevices as wide as 20 feet (6 m). Its powerful musculature means that it can travel over level ground at 30 miles per hour (48 kph), or scramble up steep slopes at 15 miles per hour (24 kph), a real advantage when it comes to evading predators.
This ram must be fairly young judging by the size of its horns. The horizontal ridges are the result of the annual growth rings which actually indicate the animal’s age. Because ram’s horns curve outwards and upwards, over time they can interfere with the sheep’s vision. Because Bighorn Sheep rely on their acute eyesight, both as an aid when jumping and gaining footholds and to detect predators, rams will rub off the ends of their horns, in a process called “brooming”, to improve their field of vision. This ram was certainly keeping a keen eye on Bob.
Bob couldn’t help but notice the rich, glossy brown colour of the ram’s coat and the white rump patches. The colouring helped the sheep to blend in well with the surrounding desert environment…a real aid to camouflage from predators such as mountain lions, coyotes, bobcats and even golden eagles. Maybe that is why we walked right past the sheep without seeing it ourselves. The colour of a Bighorn Sheep’s coat fluctuates with the seasons. In summer, it ranges from light brown to grey or even dark, chocolate brown, but by late winter, the colour fades.
As the Desert Bighorn Sheep moved about the ledge, Bob became concerned that it might descend onto the path where he was standing. Weighing between 127-316 lb (58-143 kg), and standing somewhere between 36-41 inches (91-100 cms) tall at the shoulder, the ram could easily edge Bob off the trail. He did not stick around to find out. Besides, we still had 1 1/2 miles to climb to the South Rim. We had to get on our way.
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