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Digiroo2: An application programming interface for generating null models of social contacts based on individuals' space use

Digiroo2 is an R package developed by researchers at the University of Queensland to investigate association patterns and social structure in wild animal populations. Proximity between individuals is generally considered to be an appropriate proxy for associations and pairwise association indices are the most widely used technique for analysing animal social structure. However, little attention is given to identifying how patterns of spatial overlap affect these association patterns. For example, do individuals associate randomly with others with whom they share home ranges, or do some individuals go out of their way to associate with or avoid particular individuals? This program builds a null model of random associations based on an individual's space use determined using home range methodologies. Random points may be generated within a specified home range contour or according to the Utilization Distribution (UD). Expected associations of individuals are extracted based on probability of occurrence and the proximity between home range weighted random points. Association matrices can be generated from multiple permutations for analysis using SOCPROG 2.4 (Whitehead 2009) to create 'expected' pairwise half-weight association indices (HWIs). These may be compared with the 'observed' HWIs from field observations to reveal whether pairs of animals associate more (= attraction) or less (= avoidance) than expected by chance.