Large-Scale Fence Modifications Increase Nest Survival in Sage-Grouse

Livestock grazing is the most common land-use practice in aridland ecosystems of the American West. Widespread and long-term declines of greater sage-grouse (Centrocercus urophasianus), an umbrella species for other sagebrush-associated vertebrates, has challenged land managers to find solutions to help bolster populations. Human infrastructure among western rangelands (e.g. fences) are one potential negative factor on sage-grouse populations, as nest survival – a key demographic vital rate for sage-grouse ­– can be 4x higher when placed >100 m away from the nearest fence. We implemented the first-ever, large-scale (>70 km), controlled experiment designed to evaluate changes in nest survival related to fence modifications in southwest Montana, USA. Fence modification included perch deterrents placed atop fence posts, and raised bottom fence wires (> 45 cm from the ground) intended to reduce the search efficiency of avian and ground-dwelling nest predators. We found that fence modifications increased 28-day nest survival within 100 m of mitigated fences by an average of 11.4% (90% CRI: 3.2%, 20.0%) using a Bayesian framework. The difference in survival between fence types was greater for modified fences in both low elevations and in areas with higher moisture potential. Our findings suggest that modifying fences designed to reduce the search efficiency of avian and ground-dwelling predators will likely benefit nest survival in sage-grouse across the sagebrush biome. This fence modification technique offers practitioners a tool to advance grazing practices, while reducing conflict between human infrastructure and wildlife conservation.