Sierra Nevada Bighorn Sheep

Sierra Nevada Bighorn Sheep 

Ovis Canadensis ssp. Sierrae

Calvin Koleszar

               Bighorn Sheep, one of the Golden States' most iconic animals, is under threat of extinction. In the Sierra Nevada Mountain Range, they are even more threatened than other populations in California. Although seen as a different species in comparison to its Southern California relatives, they are relatively the same in nearly all aspects except horn differentiation. 

               According to The California Department of Fish and Wildlife, by 1995 only 100 Sierra Nevada Bighorn sheep remained in sixteen distinct and historic herds. However, due to successful breeding programs and recovery plans, the population has risen to about 600 as of 2014. The map shown above is the current population distribution for the species. The Sierra Nevada Bighorn encompasses a large range of habitats from alpine meadows, rocky mountainsides, and summit plateaus. They tend to avoid dense vegetation for fear of predators. 

               Their population decline can largely be attributed to diseases from livestock in the central valley, predation, unregulated hunting, and habitat destruction. Populations went from a historic population of an estimated 1,000 pre 1900 and dropped dramatically in the twentieth century. The lowest it got was an estimated 100 in 1995, with only five herds remaining. Due to recovery efforts, herd populations have increased to encompass Yosemite National Park, Sequoia-Kings Canyon National Park and four national forests in the area. 

               The recovery plan, first implemented in 2007, has brought tremendous results within the populations. Starting in 2007, the population went from roughly 100 since 1999, to about 500 in 2012 and to about 600 in 2014. This is due in part to the California Department of Fish and Wildlife Service, along with other federal bureaucracies, management of: (1) Management of disease risk from domestic sheep, (2) translocations (augmentations and reintroductions) to increase bighorn numbers and their geographic distribution, (3) predator management to limit predation on bighorn sheep, and (4) monitoring and management of genetic variation. They have been exercised in the areas in the map above. With continued anthropogenic help, populations should continue a healthy increase within the next decade. It has been extremely successful so far. Along with that, there have also been reproduction programs to increase different heard sizes by taking female sheep from one group that has a surplus of females and implementing them into other groups that are lacking females and genetic diversity. 

               The way to sustain these populations so they may have a healthy future without the influence of humans is to limit the livestock entering their domain and spreading deadly diseases to the Bighorn Sheep. Now that there are tag limits for hunting, Bighorn Sheep are a lot less susceptible to becoming trophy ornaments. With time and spreading female sheep between herds, genetic diversity should naturally make these populations healthy and sustainable. Locals can also do their part by just staying away from these animals. Interaction with humans and outside species have taken drastic tolls on the Sierra Nevada Bighorn Sheep and if we are to see these populations thrive in the future, we need to let them grow once they become stable enough. 

Works Cited

"Recovery Program." Sierra Nevada Bighorn Sheep Facts - California Department of Fish and Wildlife. N.p., n.d. Web. 03 Dec. 2016.

"Recovery Plan for Sierra Nevada Bighorn Sheep." N.p., n.d. Web.

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