How We're Helping to Save the Peninsular Bighorn Sheep

Conservation Status: U.S. Fish and Wildlife Service – Endangered

Threats to Survival: Habitat loss and fragmentation; poaching; disease

Cross-border Landscape Connectivity

The peninsular bighorn sheep is distributed along the Peninsular Ranges stretching from the San Jacinto Mountains in Southern California to the Sierra de la Laguna at the tip of Baja California Sur. Habitat along this range is fragmented connectivity is compromised by development, international border demarcation, infrastructure projects, and roads. Together with our partners, our Population Sustainability researchers are studying bighorn sheep in the Sierra Juarez just south of the US-Mexico border to evaluate connectivity between populations in the two countries. A population survey we carried out in 2012 showed that the bighorn sheep population in the Sierra Juarez was much larger than expected, and we found bighorn sheep to be regularly using the border region. Through GPS telemetry, we are collecting detailed data on movement patterns and habitat use that will indicate the most important movement corridors and habitat features that need to be protected for bighorn sheep populations.

Population Genetics Across the Border

Our Conservation Genetics team developed a non-invasive sampling method for extracting DNA from fecal pellets from wild bighorn sheep. Fecal DNA was used to obtain genetic profiles for population genetic analysis. Using this method, we documented the population structure of bighorn sheep in the Sierra Juarez and examined connectivity with populations in southern California. We identified a genetic cluster in Mexico that is distinct from the populations further north. Although there is gene flow between the populations, the region surrounding Highway 2 in Mexico seems to coincide with the genetic break between the populations. We are planning to expand this study further south into Baja California to give us a better idea of the population structure in the southern part of the Peninsular Ranges.

Combatting Disease

Infectious diseases, particularly a disease complex affecting the respiratory tract, have caused rapid population declines in bighorn sheep in several parts of the Peninsular Ranges. Our Disease Investigations team is investigating the health status of bighorn sheep in the Sierra Juarez. We are screening biological samples for the presence of various pathogens and testing them for antibodies to detect past exposure.

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