Examining the Response of Desert Bighorn Sheep to Backcountry Visitor Use in the Pusch Ridge Wilderness Area

Abstract

Many prey species exhibit antipredator responses in the presence of humans. These responses may lead in turn to behavioral modification and spatiotemporal avoidance strategies that may have implications for long term population dynamics. Our research was developed to measure the potential effects of backcountry recreation on the behavior and distribution of desert bighorn sheep in the Pusch ridge Wilderness Area (PRWA), Arizona, USA. Human use of the PRWA was quantified across the study site using real time observer field counts and modeled use metrics derived from motion activated trail cameras (n=15) placed on six US Forest Service (USFS) trails. We conducted 113 behavioral observations at multiple spatial scales from February of 2015 through May of 2016 to quantify female bighorn activity budgets and responses to human interaction. Bighorn behavior was characterized in a generalized linear model (GLM) to examine how human use and environmental covariates affect changes in the frequency of behaviors within the bighorn activity budget. Our models indicate that interactions between bighorn and humans are complex. An increase in human activity in the PRWA correlates inversely with bighorn time spent grazing. As a potential trade off bighorn significantly increased the frequency of time bedded. These results suggest that bighorn behavioral responses to human activity may carry costs associated with avoidance, however, behavioral analysis alone is not enough to measure the extent of such costs. This research has management implications where multiple use and high levels of human activity have the potential to negatively influence the behavior of wildlife species.