Social dominance and conflict reduction in rutting male Alpine ibex, Capra ibex

Abstract

In polygynous ungulates, male mortality is thought to be linked to high-energy expenditures during the rut. However, Alpine ibex (Capra ibex) adult males show an unusually high survival during this time. Male Alpine ibex live in social groups and thus, we assumed that they might reduce energy-intensive interactions during the rut by establishing, early on, strict dominance hierarchies. To evaluate this hypothesis, we studied social interactions and mating behavior in a population of Alpine ibex in the Swiss Alps. In accordance with our prediction, and in contrast to other polygynous ungulates, male Alpine ibex decreased time spent in agonistic interactions and the number of fights during the rut compared with the prerut, irrespective of their age. Changes between access-holding males always occurred without foregoing fights and were entirely based on preestablished and stable dominance relationships. Therefore, dominant males always gained and held access to receptive females and thus managed to adopt the tending tactic. Subordinate males either left the consort pair or they adopted the coursing tactic in order to achieve temporary access to estrous females. They behaved extremely reluctantly toward dominants, as they never made use of overt aggression to challenge them or to create actively transient mating opportunities. Our study supports the hypothesis that costly intramale interactions are reduced during the mating season in Alpine ibex by the adherence to preestablished and stable dominance relationships. Accordingly, male Alpine ibex appear to be able to cut down on energy expenditures, which in turn, likely contributes to their superior survival.