Mountain sheep microsite habitat characteristics in western Arizona.

Abstract

I examined habitat use by desert bighorn sheep (Ovis canadensis medicana) in the Little Harquahala Mountains, Arizona from 1989 to 1992. I compared microsites used by male, female, and mixed-sex groups. I also compared use of microsites by sheep to random sites during the breeding and nonbreeding seasons. There were no differences in use of microsites between the breeding and nonbreeding seasons. However, microsites used by sheep had steeper slopes, more barrel cactus (Ferocactus wislizenii), higher topographic position, and more foothills palo verde (Cercidium microphyllum) than random sites. I examined seasonal diets. There were no seasonal differences between the diets of males and females. Brittle bush (Encelia farinosa), desert ironwood (Olneya tesota), fairy duster (Calliandra eriophylla), foothills palo verde, janusia (Janusia gracilis), Mormon tea (Ephedra torreyana), ratany (Krameria parvifolia), wild buckwheat (Eriogonum fasciculatum), grama grass (Bouteloua spp.), bedstraw (Galium spp.), borage (Borage spp.), and barrel cacti were present in diets all seasons. Barrel cactus is a seasonally important part of the diet, providing moisture during hot, dry periods. Forage selection is not a factor in the sexual segregation of desert bighorn sheep in the Little Harquahala Mountains. I examined habitat use by female sheep relative to the timing of parturition from 1989 to 1991. I compared range size and microsite habitat components of female sheep prior to and following parturition to random sites. Nineteen lambs were born to 10 females and 6 lambs survived $\ge$6 months. Lambs that died lived an average of 34 days. Five females did not raise any lambs that lived $\ge$6 months in any year. No female raised a lamb that lived $\ge$6 months 2 years consecutively. Females reduced their range sizes as lambing approached. Individual females used the same lambing areas repeatedly. Microsites used by female sheep were steeper and more rugged than random sites. Microsites used by females for 8 weeks after parturition had significantly less barrel cactus than was found at random sites. The traditional use of parturition sites in rugged terrain may outweigh the increased need for water by lactating females.