COS 281-1 - Divergent population parameters signal losses in resilience from global change drivers in pronghorn

Abstract: Conservation is increasingly focused on preventing species’ population losses before they occur. This requires understanding changes in the resilience, the amount of disturbance a population can endure while continuing to persist within its current state, of populations in response to global change drivers before drastic population declines occur. We used population productivity (late summer juveniles per 100 females) as an indicator of population resilience to global change drivers in 40 pronghorn (Antilocapra americana) populations across sagebrush steppe in Wyoming. Pronghorn are an iconic rangeland species that have been exposed to increasing levels of anthropogenic, climatic, and land-cover change. We (1) assessed long-term signals of population resilience and compared these to changes in population size, (2) identified patterns in large-scale global change drivers (i.e., climate, land cover change) across pronghorn habitat, and (3) determined the relationship between global change drivers and population productivity over a 35-year (1984-2019) period. We found that while Wyoming hosts some of the most abundant populations of pronghorn in North America, many herds are experiencing long-term declines in productivity, signaling potential losses in population resilience. Long-term declines in productivity were associated with increases in oil and gas development and woody encroachment. Although increasing across almost all herds, woody vegetation cover remains at low levels, suggesting that pre-emptive management may help to prevent drastic impacts to pronghorn populations. Our findings highlight the value of utilising trends in population demographics as an indicator of changing population resilience to support preventative conservation efforts in the face of rapid global change.