Bighorn Use of Escape Cover

One of the most critical elements of desert bighorn sheep habitat is cover.  Rugged topography or escape terrain provides areas for predator avoidance, lambing, bedding, and is considered to be one of the most important aspects in desert bighorn sheep habitat.

At Elephant Mountain WMA radiocollared bighorn sheep were monitored to determine habitat use.  Habitat variables considered included percent slope, elevation, aspect, habitat classification, distance to permanent water, and distance to escape terrain.

Most of the habitat use differentiation between ewes and rams appear to be related with the lambing season.  During this period ewes and rams segregate.  While ewes appear to use areas that minimize risk of predation to offspring, rams may exploit areas that offer better nutrition needed after the stressful breeding season.  This segregation may also help reduce intraspecific competition.

Overall, ewes remained within 250 yards of escape terrain, while rams generally stay within 300 yards of escape terrain.  Both ewes and rams preferred the steepest slopes available (40-79%).  However, when ewes and rams segregated, rams used a wider range of slopes (20-79%) to exploit areas with better forage.  Both ewes and rams preferred elevations from 4,500 to 5,100 feet.  Lower elevations were avoided because they lacked sufficient escape terrain. 

Desert bighorn also avoided thick brush cover.   Because bighorns rely on visual detection of predators, areas that offer ambush by predators are generally avoided. 

escape cover

Although rams used a wider range of slopes, desert bighorn sheep typically prefer steeper slopes like these that are approximately 60%.

 

escpape cover use

Seasonal distance from escape cover for ewes and rams at Elephant Mountain WMA.  Ewes remained closer to escape cover  than rams in spring and summer, coinciding with lambing season.