Minimizing the Risk of Human and Bighorn Sheep Mortality Along Roadways in Southern California

Focus Area

Wildlife & Ecosystems


Natural Resources




Under $99k


1-2 years

Research Idea Scope

In 1998, the Peninsular bighorn sheep (PBS) was federally listed as endangered throughout its distribution in the Peninsular Ranges of California. As identified by the PBS Recovery Plan (USFWS 2000), one identified threat of mortality to individual sheep is vehicle strikes on roadways. In addition to vehicular damage, collisions between vehicles and PBS also have the potential to cause human injuries and fatalities. Although vehicular collisions are a concern throughout the full range of PBS, specific (sections of) roads and highways have been identified (e.g., Highway 74, Highway 78, Interstate 8, S-22) as having a higher conservation risk, due to documented collisions or the high potential for loss of human life. In some PBS recovery regions, collisions have been documented as the highest human-caused, direct effect on PBS mortality (along with ingestion of toxic landscaping plants, such as oleander). Beginning in Autumn 2014, several wildlife agencies and conservation groups are set to undertake a two-year effort to capture and radio-collar PBS for basic monitoring and research purposes (e.g., movement and habitat use). When fully implemented, approximately one-third of all PBS will be fitted with GPS pods and VHF radio-collars (already purchased). We currently seek funding to upgrade the technology of our current collars, in order to undertake a collision minimization strategy in high-risk areas. As called for by the PBS Recovery Plan, all areas of PBS concentration near roadways or areas of movement and crossing should be signposted to warn motorists. Although the signs have been erected on some sections of roadways, PBS injuries and deaths due to vehicular collisions are still documented each year. Our minimization strategy involves erecting warning signs with the capability to receive telemetry signals (within an approximate 400 meter radius) from all telemetered bighorn sheep. In addition to containing informational warnings for motorists, these ‘receiver signs’ would utilize color-coded lights, based on the proximity of telemetered PBS. For example, no lights would flash if PBS are not detected (or detected more than 150 meters away), yellow lights would slowly flash if PBS are detected 50-150 meters away, and red lights would flash quickly if PBS are detected within 50 meters. Two costs are associated with our funding request: 1) Battery powered, solar charging warning signs (up to 15 @ $2,500) = $37,500 2) Upgrade to solar GPS Pod: UHF data transmission, sign trigger device, and geofence capability (up to 50 @ $250 each) = $12,500

Urgency and Payoff

Results from planned analyses of movement and habitat use data collected from GPS collars will help to inform future management actions related to PBS, such as the location of barrier fencing or wildlife overpasses. Additional work associated with our proposal will help to minimize future PBS and human mortality due to collisions with automobiles. Both sets of research and work will address specific local, state, and federal recovery goals and objectives, will aid in the long term adaptive management of PBS, and is an important step in the recovery process for this species.

Suggested By

Chris Gregory, PhD US Fish and Wildlife Service, Palm Springs 760-322-2070

[email protected]