Scat-based vs. Kill-site Predation Risk
We compared the predictions of total predation risk from all predators
(i.e. , sum of standardized predictions for each predator) based
on scat locations and contents to predation risk to predictions derived
at kill sites analysis at the known kill sites of collared and
uncollared elk killed by predators between 2002 and 2016 (Appendix S3,
Supporting Information). We derived kill-site models by comparing
features at 104 locations of elk kill sites (1) to 20 random points (0)
each using conditional logistic regression. Random points were generated
within 13.2 km of each kill site, to account for the largest average
movement per day of the predators (i.e. , cougar; Dickson et al.,
2005; Laundré, 2005). Landscape variables were the percentage or mean
value within a 250-m buffer around the kill sites or random location. We
used inverse frequency weighting to account for differences in number of
kills by each predator species. We evaluated models with
AICc (Appendix S4, Supporting Information) and used the
best-supported model to map predation risk to elk (Appendix S5,
Supporting Information), assuming that the sample of elk mortalities
reflected the relative predator-specific kill rates. We conducted
Spearman rank correlations between predictions from scat-based and
kill-site models at 1,000 random points, but graphically presented
smoothed graphs based on the mean risk value of 10 equal-area bins.