Friday, August 30, 2019

Bighorn Sheep

~ The bighorn sheep is a species of sheep in North America named for it‘s large horns. ~ Their horns can weigh up to 30 pounds , while the sheep themselves weigh up to 300 pounds. ~ Ovis Canadensis is the scientific name of the bighorn sheep. ~ Male bighorn sheep or â€Å"rams† are easily identified by their large spiral horns which grow throughout their lives. An adult ram's horns may measure over 30 inches each in length and reach 15 inches in circumference at the base. Female bighorn or â€Å"ewes† have slender, straighter horns that grow throughout their lives to lengths of 8-10†³ for Rocky Mountain bighorn ewes and 12-17†³ for desert bighorn ewes. Young bighorn that are less than 1 year of age are referred to as lambs. ~ At the beginning of the nineteenth century, bighorn sheep in North America were estimated to number between 1.5 and 2 million, but today less than 70,000 remain. In the late 1800's, hunting, competition from livestock grazing, and diseases introduced by domestic livestock devastated bighorn populations. Although problems with domestic livestock are subsiding, they still exist and are now accompanied by accelerating habitat loss and human disturbance. Habitat loss and fragmentation are recognized as the most significant threats facing bighorn sheep today. Natural predation from mountain lions, coyotes and bobcats also pose a risk to bighorn populations that have dwindled to low numbers. ~ An entire subspecies of bighorn sheep, the Audubon bighorn, which inhabited parts of Montana, North Dakota, South Dakota, Wyoming and Nebraska was extirpated by 1925. At various times in the early 1900's, bighorn sheep were extirpated from the states of Washington, Oregon, Texas, North Dakota, South Dakota, Nebraska, and the Mexican states of Chihuahua and Coahuila.Fortunately, many populations have been re-established through transplanting bighorn sheep from healthy populations to vacant habitat ~ Rams typically live 9-12 years, while ewes usually live 10-14 years ~ Although the diet of bighorn sheep varies according to the habitat and season, bighorn primarily eat grasses, shrubs, and forbs. Some favorite shrubs for desert bighorn sheep are acacia or catclaw, encelia, sweetbush, and krameria. Generally, bighorn sheep are opportunistic feeders that adapt their diet to the forage available. ~Mountain lions, wolves, bobcats, coyotes and golden eagles are predators of bighorn sheep. Eagles have been known to prey upon lambs, but they are unable to kill adult bighorn. Predation is usually not a problem for healthy bighorn populations; however, when bighorn are supressed by other factors, predation can limit recovery and potentially drive a population to extinction ~ The breeding season, or rut, generally extends from August-November for desert bighorn sheep and October-January for Rocky Mountain and California bighorn sheep. It is during this time that rams clash heads to fight for dominance. In each band of rams there is a dominance order, and the higher ranking rams do most of the breeding. Genetic studies are currently underway to determine the percentage of breeding completed by dominant and subordinate rams. Bighorn sheep have an approximately 6 month gestation period and most ewes give birth to one lamb per year.

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