6 Analysis of Use vs Availability

At this point, you will have data on habitat available and habitat used. Now you must conduct quantitative analyses assessing selection or non-selection of specific vegetation types. There are many methods of analyzing selection *e.g., Jacob’s index (Jacobs 1974), compositional analysis (Aebischer et al. 1993)], and appropriate statistical methods may vary depending on data normality, sample size, or specific objectives. For example, we used a Jacob’s index (Jacobs 1974) to determine selection or non-selection of vegetation types according to the following formula:

[latex]D = (r – p) / (r – p + 2rp)[/latex]

where r is the proportional amount of a vegetation type used, and p is the proportional availability of the vegetation type. The resulting values range from -1 to + 1, where -1 indicates non-selection and +1 indicates selection. To determine significance, we used a Kruskal-Wallis non parametric test (because our data violated assumptions of normality.) A Wilcoxon Rank test, with a Holms adjustment was used when significance was detected.