IUCN / SSC Cat Specialist Group - Digital Cat Library |
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| Chadwick, C.L.; Springate, D.A.; Rees, P.A.; Armitage, R.P.; O'Hara, S.J. | |
| Calculating association indices in captive animals: controlling for enclosure size and shape | |
| 2015 Applied Animal Behaviour Science (169): 100-106 | |
Indices of association are used to quantify and evaluate social affiliation among animals living in groups.Association models assume that physical proximity is an indication of social affiliation; however, indi-viduals seen associating might simply be together by chance. This problem is particularly pronouncedin studies of captive animals, whose movements are sometimes severely spatially restricted relative tothe wild. Few attempts have been made to estimate - and thus control for - chance encounters based onenclosure size and shape. Using geometric probability and Geographic Information Systems, we investi-gated the likely effect of chance encounters on association indices within dyads (pairs of animals), whendifferent distance criteria for defining associations are used in shapes of a given area. We developed asimple R script, which can be used to provide a robust estimate of the probability of a chance encounter ina square of any area. We used Monte Carlo methods to determine that this provided acceptable estimatesof the probability of chance encounters in rectangular shapes and the shapes of six actual zoo enclosures,and we present an example of its use to correct observed indices of association. Applying this correctioncontrols for differences in enclosure size and shape, and allows association indices between dyads housedin different enclosures to be compared. |
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