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• and the irrlex increase both as the number of species increases and as the <br />individuals aze distributed more and more equitably strong species already <br />present. The general formula for this index is as follows: <br />H = -E pi ~e pi <br />where: pi =decimal fraction of total individuals belonging to the ith <br />species. <br />This index varies from a value of 0 for habitats containing a single <br />species to values of 4 or 5 for ~matnities ccntaining many species, each <br />with a small number of individuals. The Shannon-Weiner species diversity <br />index rosy be used to octtpare carnrntnity oot~osition data from a variety <br />of sources. Differences in diversity may be expected for canmmities at <br />different stages of succession, in different habitats or at different <br />times of the year. <br />Habitat Affinities. Nbst animal species depend upon their ittmeiiate <br />• surroundings to provide basic requiranents far food, shelter and water. <br />Determinaticm of habitat affinities within the normal range of a species <br />may indicate its particular needs for survival and continued growth and <br />reproduction. In general, an animal's habitat may be characterized by <br />the predominant vegetation. The structural diversity of the vegetative <br />mtntomity is also important to wildlife diversity within that c~m~ty <br />(e.g. , caatamities supporting grass-forb, shrub and tree strata provide <br />greater Dover aryl feeding opportunities) . ~traluation of distribution <br />abLinrla.x~o patterns of different an;,TM,t species within and between vegetation <br />types provides a measure of habitat affinity. <br />If all animal species in an area were randomly distributed with respect to <br />vegetation distribution (no habitat affinities), then the proportion of <br />individuals of a species encountered in a particular vegetation type would <br />correspond to the proportion of the sampling effort demoted to that vegeta- <br />tion type. For example, if 30B of the small mammsl live traps were <br />established in upland sagebrush, then 30~ of the total number of individuals <br />• of all species captured over all sampling transacts would have been caught <br />-17- <br />