Thesis

Food habits of Bighorn sheep (Ovis Canadensis Nelsoni) in the San Gabriel mountains

A study was conducted in the San Gabriel Mountains of Southern California during 1979-81 to obtain quantitative data on food habits, diet quality, and preference of bighorn sheep (Ovis canadensis nelsoni). Utilizing a microhistological analysis of fecal pellets, a total of 19 forage taxa were identified. Browse species made up the majority of the diet, both on a monthly and a seasonal basis; the dominant species were Cercocarpus betuloides, Salvia apiana, Eriogonum fasciculatum, Garrya veatchi i, and Prunus ilicifolia. Grasses were eaten year-round, but were taken in significantly greater amounts in the spring. Forbs, the smallest fraction of the diet, were taken when available. Crude protein analysis of the fecal pellets showed both a monthly and seasonal variation with a high of 18.33% in the spring and a low of 10.50% in the fall. Comparing vegetation data with dietary data, the sheep showed a preference for Cercocarpus betuloides in all seasons. Salvia apiana and Eriogonum fasciculatum were preferentially selected during the winter and spring but avoided in the summer and fall. Plants which occurred commonly in the area but were avoided totally included Adenostoma fasciculatum, Eriodictyon trichocalyx, Arctostaphylos sp., and Ceanothus crassifolius.

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