Female cougars seek out denning sites within their home range. Russell (1978) identified typical denning sites as caves, space beneath uprooted trees, rocky depressions, or dense thickets.
Home ranges include hunting areas, water resources, resting areas, lookouts, and denning sites. Male home ranges vary from 40 - 800km2; females from 13 - 650km2 (Hansen, 1992). For a viable population confined to a single area with no possibility of immigration to persist for 100 years, the minimum patch size must be 1000 - 2220km2 (Beier, 1995).
The area of cougar habitat will remain relatively unchanged in Plans Build-Out because of the existing protection afforded by public lands management and rough terrain, as seen in figures 82 and 83. The anticipated decline in mule deer density with Plans Build-Out could stress existing cougar populations by reducing the food supply. The cougar however, faces a more serious problem. Interstate-15 has fragmented the regional habitat of the species, making it difficult for cougars in the two existing sub-populations to interbreed. Currently, several cougars die each year on the highway. Male cougars must cross Interstate-15 to sustain genetic diversity within the Santa Ana population; without this, inbreeding will lead to regional extinction in a few generations. A proposal to enable wildlife movement across Interstate-15 will be seen later in this report. This proposal is not assumed in Plans Build-Out.