Department of Wildland Resources, Utah State University, Utah, United States
Background/Question/Methods
As anthropogenic activity increases worldwide, many ecologists have focused on how linear features (LF) such as roads and fences impact and disrupt animal space-use behavior and how this disruption could potentially affect viability. The size and position of an animal’s Utilization Distribution (UD), in both environmental and geographical spaces, are aspects of space-use that may provide good indicators of LF impacts. How does LF density affect the size and shape of animal UDs? Does LF density affect habitat use and how the animal selects for other habitat attributes within their UD? To gain a holistic understanding of how LFs affect UD shape, size, and selection characteristics, we focused on the space-use patterns of two large ungulate species found in western North America: mule deer (Odocoileus hemionus) and pronghorn (Antilocapra americana). We constructed seasonal UDs using GPS locations from 3183 mule deer that were tracked from 2012-2021, and 325 pronghorn that were tracked from 2018-2021 within the state of Utah, USA. We then calculated the UD-weighted average of 10 environmental attributes (including LF densities), and contrasted those with their average availability within a 100 km2 reference area centered at each UD.
Results/Conclusions
We have constructed 5850, 3734, 524, and 299 UDs for deer-winter, deer-summer, pronghorn-winter, and pronghorn-summer (respectively). Across both species, sexes, seasons, and years, some individual selection ratios indicated LF avoidance (< 1) while others indicated selection ( > 1). At the population level (on average), deer neither selected nor avoided LFs, regardless of season, sex, or age class. Deer UD size, however, was negatively correlated with increasing road density across season, sex, and age class. Pronghorn, in contrast, showed a distinct population-level avoidance of both roads and fences, with these effects being stronger in the winter compared to the summer. Pronghorn is a rangeland species that rely on open landscapes to watch for and run from predators. LFs can compromise this anti-predation strategy, particularly fences as pronghorn tend to crawl under rather than jump over fences. Furthermore, pronghorn are more sensitive to cold temperatures and snow depth than other ungulates, placing confounding constraints on their space use. Mule deer, on the other hand, rely on grouping as their anti-predation strategy and are thus less impacted by LFs. In my presentation, I will demonstrate how we decomposed the variation of behavioral responses to LFs and how these responses impacted seasonal UDs.
