Social hierarchy determination in rams: A comparison of different methods

The objectives were to determine whether, in a group of adult rams: 1) the dominance index (DI) differs when calculated using absolute vs relative values using different approaches (competition for food (F), estrous females (EF) or recording of spontaneous agonistic interaction (AI)), 2) there is a consistent relationship between DI values calculated using absolute values when rams compete for F, for an EF or display spontaneous AI, and 3) there is concordance between individual hierarchical positions calculated from results of F, EF competition tests, or spontaneous AI. Twelve rams were used, and the DI was calculated using three methods: competition for food, competition for an estrous female, and spontaneous AI, in all cases assigning absolute or relative values. There was a positive correlation between the individual DI values calculated from absolute and relative measures using the food competition test, estrous female, or spontaneous AI. There was no correlation between the individual DI values obtained from the F and the EF competition tests, or from spontaneous AI. There was a positive concordance between individual hierarchical positions calculated from the F and EF competitions and those obtained using spontaneous AI. Although different methods provided differences on individual DI, the assigned value did not successfully predict the hierarchical position.