Response of desert bighorn sheep in the Mojave National Preserve to respiratory disease.
January 2015 - September 2020
A recently discovered (May 2013) outbreak of epizootic pneumonia in the deserts of southeastern California caused a substantial die-off of desert bighorn sheep in the largest and most important population in the Mojave National Preserve (MOJA). This outbreak was likely caused by pathogens transmitted from domestic sheep or goats to which native bighorn sheep mostly lack natural resistance, and could lead to extirpation of the iconic species from the Preserve. MOJA and adjacent mountain ranges support a large meta-population of desert bighorn sheep, central to the most extensive array of naturally-persisting bighorn herds in North America. Until 2013, pneumonia epizootics in this region were unknown. This study is using both existing and new data to evaluate adult and juvenile survival over multiple years across populations where pneumonia is present, to establish the demographic consequences of the current disease outbreak, and determine how strong environmental stochasticity affects the persistence and impacts of the disease. We will also use recently updated genetic data and studies of seasonal movement patterns by male and female bighorn sheep to infer risk of disease spread among populations.