Sierra Nevada Bighorn Sheep

By Cory Kasbergen

Source(https://cdfgnews.wordpress.com)

The Sierra Nevada Bighorn sheep is in big trouble. These majestic animals are listed as endangered by the United States Fish and Wildlife Service. They were listed as federally endangered on January 3, 2000 although there were emergency listed in 1999. (US Fish and Wildlife) Their ecosystem is being destroyed around them causing the Bighorn Sheep to decline drastically. This combined with a few other threats makes life difficult for these large animals. Luckily this animal has a recovery plan that will hopefully bring them away from the brink of extinction.

Source (granitechief.com)

Sierra Nevada Bighorn Sheep as their name suggests live in the mountains of the Sierra Nevada. It is a completely different sub-species to the other Desert Bighorn Sheep. These sheep live on the steep rocky slopes of the mountains to stay away from predators. However, Bighorn Sheep must go down to the meadows of the Sierra Nevada to eat grass. The meadow has to be near an escape route that allows the Bighorn Sheep to out climb their predator. The main predator to Bighorn Sheep are mountain lions which usually only are a threat to the young and diseased. Sierra Nevada Bighorn sheep are about three foot tall at the shoulders and the females usually weigh 140lb while the males weigh about 220lb. They are a K-selected species having only one lamb per year. This contributes to their listing because they have a hard time replacing individuals that are lost.

The Sierra Nevada Bighorn sheep are currently endangered from a few different factors that manage to decimate the population. The first die off occurred during the gold rush era of California. The miners would kill the bighorn sheep for a hearty meal. The largest factor to their endangerment are disease carrying sheep. One nose to nose contact is enough to spread deadly disease that easily kill bighorn sheep. In the 1980s and 90s 60% of Sierra Nevada Bighorn sheep were killed by diseases carried by domestic sheep. A big part of the recovery plan for this subspecies of bighorn sheep is keeping other sheep away from them. Like most species bighorn sheep have suffered from habitat degradation. The largest offender are highways and roads. They physically separate the different herds and make it much easier for each herd to go extinct locally. Another threat to Sierra Nevada Bighorn Sheep are mountain lions. Mountain lions prey on the younger bighorn sheep and bring down the overall population. They also seem to make the Bighorn sheep stay out of the fertile valleys where the grass is and stay on the mountain tops to stay away from the mountain lions. This causes the Bighorn sheep’s fitness to go down. For this problem unfortunately nothing can be done as mountain lions are a protected species.

  Source(https://www.wildlife.ca.gov/Keep-Me-Wild/Lion)

Source (www.Flickriver.com)

Sierra Nevada Bighorn sheep were listed as endangered by the US Fish and Wildlife service on April 20,1999. The recovery plan hopes to bring these large mammals back from endangered and hopefully have a stable population. The recovery plan includes trying to obtain private lands from landowners where it is deemed an important habitat for bighorn sheep. Trans locations from one herd to another are also used to keep herd sizes up. When a herd size is too small or does not have enough females researchers will take females from other herds to keep every herd alive and well. A captive breeding program is also part of the program to aid in translocations. Another part of the plan is to keep domesticated sheep and goats away from Bighorn Sheep. This will prevent inter mating that produces hybrids and the diseases that domesticated sheep have. The recovery plan also has a team ready for a pneumonia outbreak that could potential wipe out the remaining Bighorn Sheep. Under this plan wildlife researchers will also manage human contact and activities that can potential harm the Bighorn Sheep. Since the population is low genetic diversity is also low. The captive breeding program hopes to bring in more diversity so that the species is not as susceptible to disease and extinction. Lastly the recovery plan also pays for an educational aspect for the general public. This mostly occurs in Yosemite National Park where visitors are taught the dire straights that Sierra Nevada Bighorn Sheep find themselves in.

 Source (California Department of Fish and Wildlife)

Figure One Population of Bighorn Sheep 

                                                             Source (ESAsuccess.info)

The population of the Sierra Nevada bighorn sheep was believed to be numbered in the thousands before the California gold rush. As shown in figure one the population started to decline from 300 bighorn sheep in 1990 to under a 100 in 1999. As already explained this was mostly due to disease and predation by mountain lions. Luckily after being emergency listed in 1999 the population slowly started to climb to a more stable herd number of over 400. Now with the recovery plan the population is mostly stable. The population is trending upward and hopefully stays that way. Thank you for reading this blog and now you know the plight that Sierra Nevada Bighorn Sheep find themselves in. 

References

Recovery Plan for the Sierra Nevada Bighorn Sheep. Rep. Sacramento: California/Nevada Office of                    t                  the U.S. Fish and Wildlife Service, 2007. Web. 29 Nov. 2015.

"Sierra Nevada Bighorn Sheep." National Park Service,. Yosemite National Park, n.d. Web. 28 Nov.             2                 2015.