The Sierra Nevada Bighorn Sheep - Keaton Bates

The Sierra Nevada Bighorn Sheep

March 6th 2018

 By Keaton Bates

Image: http://sanjoaquinsoundings.blogspot.com/2016/04/a-still-small-voice-and-holy-spirit-as.html

Species Description

The Sierra Nevada Bighorn sheep is a type of bighorn sheep that is solely found in the Sierra Nevada mountain range. The coloration of their fur varies from white to brown depending on the current season. They were once a species seen very often in the Sierra Nevada, an animal admired and written about by John Muir. He wrote about their beauty and perfect adaption to their environment. They possess sturdy hooves that are adhesive on the underside, making them ideal for steep, rocky terrains. They are typically found in groups of all the same gender, with the exception of mating season (Cassel). Interestingly enough, they typically stay with the same group their entire lives (typically 8-12 years). They are herbivores that prefer to graze on various kinds of grasses and vegetation depending on what the seasons provide. Typically lambs are born in late spring or early summer. Unfortunately, the Sierra Nevada Bighorn sheep is now listed as an endangered species and struggling to maintain a healthy population numbers for a couple reasons (Sierra Bighorn).

Geographic Population Ranges

Sierra Nevada Bighorns are usually spotted in open areas all throughout the Sierra Nevada including Yosemite National Park. They prefer rocky areas on steep inclines or canyons that offer great escape routes. Ideally, they will look for high elevation areas of this type so as to spot any danger from miles away and have time to escape to terrain too treacherous for predators. For this reason they are never seen in forested areas with high vegetation cover. During the winter months, some sheep climb to higher elevations while others descend below the snow line in search of more abundant food sources. The image on the left shows the populations of the all the recovery units of Sierra Nevada Bighorn Sheep. On the right, shows the disparity of the the Sierra Nevada Bighorn Sheep to the other two Bighorn species in California (the Peninsular Bighorn & the Desert Bighorn). Recently, the endangered species has experienced positive growth, with an estimated 500+ individuals (Matson).

Image (left): https://newsela-test-files-f331e.s3.amazonaws.com/article_media/extra/20140428_BIGHORN_SHEEP.jpg
Image (right): https://www.dfg.ca.gov/wildlife/Bighorn/images/bighorn_CA.gif

Listing Date and Type of Listing

The Sierra Nevada Bighorn was listed as a federally endangered species on January 3rd, in the year 2000. In 1995 the population hit an all-time low of roughly 100 individuals spread throughout the Sierra Nevada range. Fortunately since it's listing in 2000, the population increased steadily. Currently, their is an estimated 300 individuals. The main reasons for endangerment include disease, predation, unregulated hunting, and lack of available habitat due to fire suppression management that has separated many sheep, making it breeding more difficult and keep the genetic diversity high.  

Cause of Listing and Main Threats

Although heavy predation from Mountain Lions have caused significant reductions in the sheep's population size, disease is by far the biggest threat to the Sierra Nevada Bighorn. Ironically, domesticated sheep in the area are the main cause and spread of the disease. Domesticated sheep have transmitted a type of pneumonia that knocked out hundreds of Sierra Nevada Bighorn in the      1980's, reducing its population to an all-time low in '95. 
Image: http://www.dfg.ca.gov/snbs/NH_Survival.html

Biologists releasing Sierra Nevada Bighorn into the Cathedral Range

(2015)

The Recovery Plan

As of 1999, the lead group responsible for the recovery of the Sierra Nevada Sheep is the CDFW (California Department of Fish and Wildlife). In their Recovery Plan, they have outlined three immediate actions needed and two future actions. The immediate actions include(1) Protecting existing herds by maximizing population growth and limiting predation,(2) Trans-locating  herds during winter times to more optimal locations, and (3) preventing contact between domesticated sheep so as to reduce disease transmission (Benz et al). Future actions consist of introducing sheep to vacant herds for recovery and monitoring the genetic diversity of herds. The rough estimated cost of this recovery plan is $21,730,000 according to the CDFW. Everything going to plan, they estimate the recovery to take about a decade (Wehausen). 

image: https://www.nps.gov/yose/learn/nature/sheep-biology.htm

For the full recovery draft visit:https://ecos.fws.gov/docs/recovery_plan/080213_1.pdf

So...What Can you do to Help?

Unregulated hunting of the Sierra Nevada Sheep is another cause of endangerment. To begin with, not hunting this species is a direct way of helping with the recovery and restoration. In addition, contacting governmental officials to insure that the Sierra Nevada's continue to be public land is crucial to maintaining suitable habitats for the sheep. As private land owners, they are free to change their property as they please, which would most likely lead to the degradation of the the rocky, steep, open habitats that bighorns thrive in. In addition, foundations have been started to help with recovery. The primary one I found is called The Sierra Nevada Bighorn Foundation. Founded by two Ph.D wildlife ecologists, the foundations aims to create awareness for the species and offers memberships with proceeds going directly to recovery efforts. 

For more information visit: https://sierrabighorn.org/the-foundation

Resources and Links

Full Recovery Plan -
https://ecos.fws.gov/docs/recovery_plan/080213_1.pdf

Sierra Nevada Bighorn Foundation - 

https://sierrabighorn.org/the-foundation

National Park Service Article - 

https://www.nps.gov/yose/learn/nature/sheep-biology.htm 

History of Sierra Nevada Bighorn Sheep Recovery - 

https://www.nps.gov/yose/learn/nature/sheep-history.htm 

Works Cited (MLA) 

Matson, Dale. “Soundings.” A Still Small Voice And The Holy Spirit As Life Choreographer, 1 Jan. 1970, sanjoaquinsoundings.blogspot.com/2016/04/a-still-small-voice-and-holy-spirit-as.html. 

“Sierra Bighorn.” The California Department of Fish and Wildlife, The Fresno Bee, 2004, newsela-test-files-f331e.s3.amazonaws.com/article_media/extra/20140428_BIGHORN_SHEEP.jpg. 

“Recovery Program.” Calfornia Department of Fish and Wildlife, 2004, www.dfg.ca.gov/SNBS/RecoveryHome.html. 

California Department of Fish and Wildlife. “Sierra Nevada Bighorn Sheep.” Sierra Nevada Bighorn Sheep - Survival - California Department of Fish and Wildlife, www.dfg.ca.gov/snbs/NH_Survival.html.

Cassel , Bonnie. Sierra Nevada Bighorn Sheep Description and Biology. 3 Aug. 2017, www.nps.gov/yose/learn/nature/sheep-biology.htm++++.

 

Benz , Carl et. al. “Draft Final Recovery Plan - Sierra Nevada Bighorn Sheep.” California/Nevada Operations Office, 31 Aug. 2007, p. 199.

Wehausen, John D. “About The Foundation.” SierraBighorn.org, sierrabighorn.org/the-foundation.