THE RECOVERY OF THE PENINSULAR BIGHORN SHEEP

PRESENTED BY: PAIGE GILL

March 18, 1998 was a pivotal day for the population of bighorn sheep occupying the Peninsular Ranges of Southern California.  On that date, this population was listed as

Photo Courtesy of Jeff Young

endangered by the US Fish and Wildlife Service due to factors including, but not limited to, habitat loss, declining population, and low recruitment associated with disease and high predation.  Peninsular bighorn sheep have a recovery priority of 3C, illustrating the fact that although they face a high degree of threat, their potential for recovery is high.  Peninsular bighorn sheep belong to the Bovidae family and are designated as a distinct population subspecies of Ovis canadensis nelsoni.

Source: California Department of Fish & Wildlife

As a diurnal species, bighorn sheep are mostly active during the day and tend to stick close to their native home range.  Females, called ewes, stick together in smaller groups to take advantage of of group alertness and decrease the risk of predation.  On the contrary, rams tend to have a wider range, moving between ewe groups.  Bighorn sheep are rarely able to outrun predators, therefore they require a habitat that offers escape terrain which is generally steep, rugged areas where they can utilize their climbing skills.  Peninsular bighorn sheep differ from other subspecies in that their habitat is generally below elevations of 4,600 feet due to the dense vegetation found at higher elevations that decreases the visibility used in avoiding predators.

Although the range for Peninsular bighorn sheep encompasses the Peninsular Ranges of Southern California and crosses the US/Mexico international border, only the populations

Source: California Department of Fish & Game

located in California are listed as endangered.  The recovery area for Peninsular bighorn sheep is divided into nine subpopulations that encompass Riverside, San Diego, and Imperial Counties.  The map for the recovery areas (shown to the left) can be found by clicking here. According to the data provided in the 5 year review conducted by the US Fish and Wildlife Service, the population of the Peninsular Bighorn Sheep has increased from an estimated 335 adults in 1998 to an estimated 955 adults in 2010.  This represents an impressive 185% increase in the adult population over a 12 year period.  The subpopulation area showing the most increase was area 9: Carrizo Canyon, Tierra Blanca Mountains, Coyote Mountain area, which went from an estimated 28 adults in 1998 to an estimated 232 adults in 2010.  This is an astounding 729% estimated population increase for this area, which shows that recovery efforts have been successful.  A full version of the 5 year review can be found by clicking here.

The recovery plan outlined in 1998 by the US Fish & Wildlife Service describes three main strategies to aid in the recovery of the Peninsular bighorn sheep.  Below is an outline of the main strategies listed in the recovery plan along with examples of action items associated with each strategy:

Promote Increase in Population & Protection of Habitat

Protect, improve, restore and acquire habitat necessary for the growth of the Peninsular bighorn sheep population

Initiate or Continue Research Programs Necessary to Monitor and Guide Recovery Efforts
Monitoring abundance
Development of population models
Conduct research on the relationship between bighorn sheep, mountain lions, mule deer, and the habitat 

Create and Initiate Education and Public Awareness Programs
Distribution of information related to recovery efforts
Development of additional education programs related to the recovery effort

Although significant improvements have been made in the recovery efforts for Peninsular bighorn sheep, the 5-year review conducted in 2008 by the US Fish & Wildlife Service

Source: 5-Year Review conducted by the US Fish & Wildlife Service

shows that there are still significant threats to the growth in population.  Factors of major consideration are: urbanization, road and highway use, invasive non-native plants, and drought and climate change.  The road to recovery for the Peninsular bighorn sheep has been long, but significant improvements have been made.  As threats to their continued population growth are managed, the populations of these great animals will continue to increase.

Sources:

https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=43873&inline=true

http://ecos.fws.gov/docs/recovery_plan/001025.pdf

https://www.dfg.ca.gov/wildlife/Bighorn/Desert/Peninsular/Images/Maps/phs_recovery_region_map_6-2011_draft.pdf 

http://ecos.fws.gov/tess_public/pub/speciesRecovery.jsp?sort=1 

https://www.dfg.ca.gov/wildlife/Bighorn/Desert/Peninsular/Conservation.html