Resource Selection by an Endangered Ungulate: A Test of Predator-Induced Range Abandonment
Table 1
Hypotheses and corollary predictions regarding the influence of direct and indirect predation risk, forage availability, and tradeoff of forage at low versus high elevation on habitat selection. For each of three general hypotheses, the prediction of selection for a corollary predictor is denoted (+), and avoidance denoted (−), where relevant, for female and male Sierra Nevada bighorn sheep in the Sierra Nevada, California, USA, 2002–2007.
Hypothesis and corollaries
Hypothesis supported
(I) Habitat selection influenced by risk of predation
(A) Direct predation risk; surfaces generated from probability density functions of
Yes
No
Active mountain lions
(−)
(+)
Locations where bighorn sheep were killed and cached by mountain lions
(−)
(+)
(B) Indirect (habitat-mediated) predation risk
Yes
No
Elevation
(+)
(−)
Slope
(+)
(−)
Terrain ruggedness (all radii)
(+)
(−)
Convexity at location (15–30 m radius)
(+)
(−)
Convexity within flight distance (100–150 m radius)
(−)
n/a
Rock cover
(+)
(−)
Tree cover
(−)
(+)
(II) Habitat selection influenced by forage availability
Yes
No
Snow cover
(−)
(+)
Solar radiation
(+)
(−)
Vegetation index
(+)
(−)
(III) Tradeoff of forage versus risk of predation reduced during drought
Yes
No
NDVI low elevation minus NDVI high elevation, above average annual precipitation
(+)
n/a
NDVI low elevation minus NDVI high elevation, below average annual precipitation
