Diets of Desert Bighorn Sheep

One of the most essential elements to managing a species is understanding their dietary preferences.  This is especially true of desert bighorn sheep as recovery efforts begin to expand to other mountain ranges in west Texas.  Knowledge about dietary preferences can help scientists and managers monitor sheep populations and habitat to make scientifically based management decisions.  In a study on Elephant Mountain WMA we evaluated the diet of a successfully reintroduced bighorn population. 

Fecal samples were collected in order to determine differences between rams and ewes, seasons, and mountain ranges.  Diet composition was broken down by genus, species, and forage class.  From September 1998 through August 2000 432 fecal pellet groups (209 rams, 209 ewes, and 14 lambs) were collected.  Ninety-four plant species were identified in the diets.  Forage classes were broken down into browse, forbs, grasses, and succulents.  For both rams and ewes diets consisted of 50% browse, 35% forbs, 11% grasses, and 4% succulents.

Predominant plants based on frequency included globemallow, muhlys, wild buckwheat, fourwinged saltbush, trailing ratany, esperanza, goosefoot, ephedra , and honey mesquite.

Ram and ewe diets were very similar.  However, some seasonal differences did occur.  During winter rams consumed more forbs (35%) than ewes (20%).  Grasses made up only 6% of ram diets, while ewes consumed 28% grasses during winter.  Browse and forbs dominated lamb diets during spring and summer. 
Desert bighorn sheep are opportunistic, and able to adapt their diet depending on available forage.  However, a diversity of vegetation is important and helps provide suitable forage throughout the year.  Browse appears to be the most important forage class for desert bighorn sheep populations in west Texas.  Forbs also play an important role in bighorn sheep diets when available, and especially for lambs during spring and summer.

Desert bighorn sheep habitat is not exclusive to that of other ungulates including elk, aoudad, mule deer, and javelina.  Resource managers and landowners should be mindful of the potential for competition for forage that may exist between these species. 


bighorns

The diet of ewes differed slightly from rams where ewes consumed greater amounts of grasses.

 

diet

Percentage of each forage class in desert bighorn sheep diet at Elephant Mountain WMA, Sep 1998 – Aug 2000.