Resource Selection by an Endangered Ungulate: A Test of Predator-Induced Range Abandonment

Figure 5

Odds ratios (mean and 95% CI) from resource selection functions (RSFs) for Sierra Nevada bighorn sheep. Top: continuous predictor variables in best-fitting models of female (a) and male (b) bighorn sheep. Predictors included risk surface from locations of active mountain lions (LNRISK); potential relative radiation (PRR); terrain ruggedness over radii of 20 m (RUG20), 30 m (RUG30), 100 m (RUG100), and 150 m (RUG150); slope (degrees; SLOPE). Bottom: odds ratios for normalized difference snow index (NDSI) and binary variables in best-fitting models of female (c) and male (d) Sierra Nevada bighorn sheep. Predictors included convexity over radii of 15 m (CVX15), 100 m (CVX100), and 150 m (CVX150); rock cover (ROCK); and tree-shrub cover (TRESH), Sierra Nevada, California, USA, 2002–2007. Odds ratios represent the odds of use (where 1 represents 1 : 1 chance, i.e., no selection) for every one unit change in continuous predictors; LNRISK, SLOPE, and NDSI, and for each 100 unit change in rescaled variables PRR, RUG20, RUG30, RUG100, and RUG150. Odds ratios represent the odds of use, given the positive case for each binary predictor, relative to the absence of the binary predictor for, CVX15, CVX100, CVX150, ROCK, and TRESH.

(a) Female continuous

(b) Male continuous

(c) Female NDSI and binary

(d) Male NDSI and binary