Bighorn sheep: Colorado’s amazing rock climbers
October 18, 2010
Two different people recently sent me amazing pictures that have been all over the Internet of bighorn sheep climbing up and down what seems to be an impossibly steep wall of a dam; a wall that would challenge a rock climber, but they are not using protection like ropes, pieces or harnesses. The claim is that they are climbing the Buffalo Bill Dam in Wyoming, but actually I found that the picture is really of ibex climbing a dam in Italy. In any case I’m going to write about the bighorn sheep, which is the state animal of Colorado and are amazing rock climbers.These agile animals, the bighorn sheep, have split hooves and rough hoof bottoms for natural grip and balance. The halves of each hoof can separate, so they can cling firmly to steep, rocky terrain. The hooves are actually hard at the outer edge and spongy in the center. The soft, rubbery, padded soles also help with balance and add traction as they scamper across uneven, slippery terrain, narrow trails and up sheer rock faces.Bighorn sheep get their name from the large, curved horns of the males, or rams. Females or ewes have short, slightly curved horns. As rams mature, their horns develop the characteristic curl, and the age of a ram can be determined from the growth rings of his horns. The bighorn sheep range in color from light brown to grayish or dark, chocolate brown, with white on the rump extending down the legs. In the summer, they shed the top level of their fur, and they look somewhat scruffy during the shedding period.Bighorn sheep are generally found on high, rugged, sparsely wooded mountain slopes, cliffs, and rocky, lightly wooded canyons and foothills and they migrate between high mountain slopes in summer, and lower slopes in winter. They return to an established bedding spot at night, which is an area about 4 feet wide and packed down to about an inch. This bed is usually marked with their urine and is edged with droppings. They will return to these beds and stay for extended periods during yearly migrations and may use them over again for several years.Bighorns from the Rocky Mountains are relatively large, with rams around 500 pounds and ewes around 200 pounds. The rams’ horn can weigh up to 30 pounds – equal to the weight of the bones in the male’s body! Prior to the mating season, the rams attempt to establish a dominance that determines their mating rights. It is during this period that most of the characteristic horn clashing occurs, although this behavior may occur to a limited extent throughout the year. Fighting for dominance, males face each other, rear up on their hind legs, and hurl themselves at each other at speeds of up to 20 mph. The animal’s thick, bony skull usually prevents serious injury but chips of horn may fly about, and blood may be seen oozing from ears and nose. The losing ram, exhausted or injured, lowers his head in submission, and the winner strides away to claim the ewe.Ewes usually breed at 2-1/2 years of age and have a six-month gestation period. The rut begins in October or November with one, or rarely two, lambs being born in May or June. The lambs are then weaned when they reach 4-6 months. Lambs are born on high, secluded ledges protected from bighorn predators such as wolves, coyotes, and mountain lions, but this does not protect them from golden eagles. Young can walk soon after birth, and at one week old each lamb and its mother join others in a herd. Lambs are playful and independent but their mothers nurse them for four to six months. The sexes separate in the spring. Rams band together in groups of 3 to 5 and move to higher ranges during the summer. The ewes with their lambs and yearlings form groups of 5 to 15 and move to separate high mountainous areas.Bighorn sheep originally crossed over the Bering land bridge from Siberia and the population in North America peaked in the millions. By 1900, the population had diminished to several thousand. Bighorn die-offs originally started as settlers moved west bringing with them bands of domestic sheep which came in contact with bighorn sheep. Diseases including pneumonia were spread from domestic sheep to bighorn, almost wiping out the bighorn sheep populations. Conservation efforts (in part, by the Boy Scouts) have restored the population.Bighorn Sheep are considered good indicators of land health because the species is sensitive to many human-induced environmental problems.Breckenridge resident Dr. Joanne Stolen is a former professor of microbiology from Rutgers now teaching classes at CMC. Her scientific interests are in emerging infectious diseases and environmental pollution.