Sierra Nevada Bighorn Sheep Progress Towards Recovery

Sierra Nevada bighorn sheep are an endangered species under Federal and California law. There is a real opportunity to recover Sierra bighorn because their habitat is intact and there is broad public and agency support for the effort. Sierra bighorn are one of only two only federal endangered species in Yosemite National Park and Sequoia-Kings Canyon National Parks (along with the mountain yellow-legged frog); these parks are excited to see this iconic mammal restored as part of the native fauna within their boundaries. Down-listing goals can be met in the next decade if recovery actions are implemented. Translocations to augment newly created herd units are still needed while the existing herds that serve as translocation stock must be protected. Recovery goals are outlined in the Sierra Nevada Bighorn Sheep Recovery Plan (PDF).

Population Growth for Each Herd Unit (Ewes)

In bighorn sheep, the number of adult ewes determines how quickly a population can grow or recover from losses. Because of this, the health of a population is often gauged by the number of ewes present. This graph shows population trajectories for adult and yearling females from 1999-2020 based on a combination of population estimates (marked resight and minimum count) for 6 herds in the Sierra with annual population data.

The number of Sierra bighorn ewes has fluctuated from 1999-2020 in 6 herds that were counted annually.

 

Numerical Recovery Goals

The population goal for downlisting to threatened status is 305 females (for >1 year).

Sierra bighorn recovery progress. All of the required herd units for delisting are occupied for each of the four recovery units.

The population must be distributed among 12 of 16 herd units within the 4 recovery units. For delisting the required number of bighorn sheep must persist for a minimum of 7 years without management intervention. Currently, all 12 of the 12 required units have bighorn sheep, as do 2 of the non-required herd units.

Sierra bighorn progress towards recovery. Southern and Central recovery have mets goals; Kern and Northern have not.

The numerical and herd unit / recovery unit occupation is tabularly summarized below. Achieving final recovery goals will require additional translocations and augmentations. These ewes will likely be supplied by the Mt. Baxter, Sawmill Canyon and Wheeler Ridge herds. Therefore, surplus animals must be available for removal from these herds (see map of herds).

Recovery Unit Herd Unit Downlisting / Delisting
Criteria
Recovery Unit #Ewes
Current Population
Recovery Unit
(2020)
Current Population
Herd Unit
(2020)
Plan to Achieve
Numerical Goals
Kern Laurel Creek* 50 15 2 Translocation
Big Arroyo* 13 Translocation
Southern Olancha Peak* 155 169 30 Natural growth
Mt. Langley* 17 Natural growth
Mt. Willamson* 13 Natural growth
Bubbs Creek** 14 Natural growth
Mt. Baxter* 56 Natural growth
Sawmill Canyon* 35 Natural growth
Taboose Creek* 4 Natural growth
Black Divide 0 Translocation
Coyote Ridge 0 Translocation
Central Wheeler Ridge* 50 50 44 Natural growth
Convict Creek* 6 Natural growth
Northern Mt.Gibbs* 50 31 22 Natural growth
Mt. Warren* 7 Natural growth
Green Creek 0  
Twin Lakes 0  
Cathedral Range** 2 Translocation


Key

  *         Required, currently occupied
  **       Not Required, currently occupied