Mountain sheep (Ovis canadensis mexicana) in the Pusch Ridge Wilderness (PRW), Santa Catalina Mountains, Arizona have abandoned historic habitat and now occupy 44 km². I used univariate analyses to quantify differences of physiographic and vegetational variables between abandoned habitat and habitat that is still used by mountain sheep. A discriminant function model characterized the magnitude of the differences between the 2 habitats. Habitat that supports mountain sheep has less human disturbance and is more open with more side oats grama (Bouteloua curtipendula), red brome (Bromus rubens), brittle bush (Encelia farinosa), and forb cover, but less ground cover, bush muhly (Muhlenbergia porteri), and turpentine bush (Haplopappus laricifolius) than habitat that was abandoned by mountain sheep. Fire is important in still used habitat because it reduces tall plants that obstruct mountain sheep vision. Human disturbances should be minimized in mountain sheep habitat.

The number of desert bighorn sheep (Ovis canadensis mexicana) in Pusch Ridge Wilderness (PRW), Santa Catalina Mountains, Arizona has declined to between 50 and 100 animals. Sheep have restricted movements to the southwest corner of PRW. I developed a model based on nitrogen (N) content of forage and forage quantity to measure seasonal changes in nutritional carrying capacity of sheep use areas in PRW. Forage based estimates of animals numbers were greater for April to September than for October to March. My study suggests that forage is not limiting desert bighorn sheep in PRW and illustrates the potential to support more desert bighorn sheep in PRW than the current population. Seasonal fluctuations in range productivity should be examined in relation to human disturbances proximal to desert bighorn sheep habitat and fire management programs for PRW.

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The interaction between Xylocopa californica and Chilopsis linearis was used to test the hypothesis that nectar robbing is costly to plants. No evidence for these costs, either in terms of decreased pollination or increased energy demands, was found. In fact, the mean number of seeds per fruit and the mean individual weight of seeds per fruit was higher from fruits that developed from robbed flowers than from fruits that developed from unrobbed flowers, indicating that the presence of Xylocopa californica enhanced pollination. Chilopsis linearis pollen was isolated from the tips of the abdomens of robbing Xylocopa californica and it was determined that these bees could be transferring pollen from flower to flower as they position themselves to rob. This association was found to be one of mutual benefit rather than one of exploitation.

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