Bighorn Sheep, Ovis Canadensis
The bighorn sheep (Ovis Canadensis) can be found in North America. There are three currently accepted subspecies of this sheep. The range of the bighorn sheep depends on these subspecies. The Sierra Nevada and Rocky Mountain bighorn sheep dwell in the cool mountainous areas of the United States and Canada, while the Desert bighorn sheep are native to the hotter desert areas of the southwestern United States. Bighorn sheep prefer habitats located in rocky, grassy slopes, and alpine meadows. They will live in different altitudes depending on the season. In winter, bighorn sheep prefer altitudes of 2,500 to 5,000 feet, while in summer they will move higher to altitudes of up to 8,500 feet.
There are three species of sheep inhabiting North America and Siberia today, including the bighorn sheep, Ovis dalli, and snow sheep. Sheep migrated from Siberia into North America using the Bering land bridge during the Pleistocene Era, as many other mammals did. Approximately 600,000 years ago, the bighorn sheep and dall sheep separated from the snow sheep, their closest ancestor. Hybridization between these sheep makes it difficult to ascertain their status. These sheep numbered in the millions at one time, and then decreased in number to the thousands. Luckily, bighorn sheep have had the help of humans to revive their populations.
As their name suggests, bighorn sheep have large horns that can weigh up to thirty pounds. Male sheep, rams, have larger, more curved horns, while females, called ewes, have smaller and less shapely horns. The coat of the bighorn sheep can vary from shades of brown to light shades of grey, but the lining of the backend and back of the legs is white. Rams can weigh between 127 and 316 pounds, while ewes weigh between 75 and 188 pounds. The body length varies between sexes as well, with males having an average body length of up to 6.5 feet and females having a length of up to 5.5 feet. The Rocky Mountain bighorn sheep is larger than the other subspecies of bighorns, with males occasionally exceeding 500 pounds and females weighing more than 200 pounds. The smallest of the bighorn sheep are the Sierra Nevada bighorns. Males can weigh up to 300 pounds while females usually weigh around 140 pounds. Male bighorns have adapted skulls that allow them to fight and play with their large horns without causing damage.
Bighorn sheep do not usually follow a dominant male, and they live in big flocks. This changes slightly when mating season occurs, when males will fight for a place in a hierarchy that determines which males can mate with which ewes. Rams do not typically use “horn-clashing” year round, although this does occur, but they will use this form of fighting during mating season. Females will not usually fight unless they are seeking a higher status that coincides with age, or they are looking to join the hierarchy as juveniles.
There are typically three courtship rituals that are displayed by bighorn rams. The most common method used, called tending, is when males will follow a ewe in estrous and protect her from danger. This is very effective because tending requires strength and energy. The second most widely used method is called coursing, which involves rams fighting for ewes that are currently being tended to, and it is not very effective. Occasionally males will use a method called blocking, where they will prevent a ewe from entering a tending area before she even enters estrous.
Mating season in good climates is usually around the month of November. Ewes are pregnant for six months, and will usually give birth to one or two lambs in May. In the Rocky Mountains, pregnant ewes will move into alpine regions in spring, most likely to avoid predation. This causes the sheep to move out of areas with abundant food supplies, which may affect the lambs when they are born. Ewes will usually give birth within the first two weeks of the “lambing” period, and these lambs are more likely to survive than those born in late May. This is because lactating ewes who do not have a sufficient food supply cannot give the lambs the nutrition they need. Each newborn lamb can weigh up to ten pounds and are able to walk only a few hours later. They are weaned at four to six months. Ewe sheep will live longer than males, at ten to fourteen years, while rams will live for nine to twelve years.
Escaping most predators is relatively easy for bighorn sheep, as they are well adapted to traversing steep, rocky slopes, but deaths from falling do occur. The predator that is best at reaching them in these areas is the cougar, but all bighorn sheep are also threatened by bears and wolves. Lambs are at risk of predation by bobcats, lynx, golden eagles, and coyotes. Humans will hunt the bighorn sheep as well, as a game animal. Bighorn sheep are susceptible to many diseases that sheep carry, including pneumonia and scabies.
The diet of the bighorn sheep consists of shrubs and grasses, which they browse from in different fashions. Males will stop and eat, and then ruminate their food, while females will walk and graze, most likely to protect their young from harm. This leads to males growing bigger, due to better digestion of food. The bighorn sheep will also go to natural salt licks to obtain minerals.
Although the bighorn sheep, or Ovis Canadensis, is not an endangered species, the desert subspecies is. Prior to WWII, domesticated sheep, disease, and hunting contributed to the loss of many bighorn sheep. By approximately 1990, these sheep numbered in the thousands, a huge decrease from their prior numbers of around two million. Luckily, a reduction in hunting and domesticated sheep brought the bighorn sheep numbers up. In the 2010-2011 hunting season, nineteen hunting permits were given to hunters.
In Arizona, boy scouts played a large role in saving the regional sheep populations. They created a stat-wide campaign in 1936, influenced by the “Father of scouting” Major Frederick Russell Burnham. Burnham had noted that less than 150 bighorn sheep existed in the Arizona Mountains, and rallied the boy scouts by contacting the executive of that time, George F. Miller. Many other important people in Arizona joined the cause, and schools were given the task of creating posters for the effort. Prizes were given out, and the winning poster was made into neckerchiefs for the ten thousand boy scouts of that time. Groups like Izaak Walton League, National Wildlife Federation, and the National Audubon Society also joined in the efforts to save Arizona’s bighorn sheep.
Because of these efforts, two game ranges were created in 1939: Kofa National Wildlife Refuge and Cabeza Prieta National Wildlife Refuge. Over 1,500,000 acres were given to these refuges and waterholes were created for the bighorn sheep. The bighorn sheep had such an impact on the boy scouts that it is now their official mascot in Arizona.
Bighorn sheep have had a significant cultural influence on humans. For the Crow people, or Apsaalooka , these sheep were revered. Today, the tribal lands of the Crow people have the name of the Bighorn Mountain Range. The sheep are hunted for their horns and meat, and these are used for food, hunting trophies, and in ceremonies. In Alberta, Canada, the bighorn sheep is the provincial mammal and in Colorado it is the state animal, which can be seen in the Colorado Division of Wildlife logo. In American history, Lewis and Clark recorded many sighting if the bighorn sheep, which they confused for Asiatic Argali, or mountain sheep. In the map produced after their expedition, a tributary of the Yellowstone River was named Argalia Creek, and a branch of the Missouri River was named Argalia River. These rivers are located in what is today Montana, but neither of the names for these rivers were kept. On the same map, a tributary of the Yellowstone River was called Bighorn River, and branch of that river was named the Little Bighorn River and these names have been kept. Bighorn sheep are important to humans because they can gauge the health of land, and are sensitive to human caused environmental problems.