Horns and Fighting in Male Spanish Ibex, Capra pyrenaica

Abstract

As adult body mass is reached fighting force is greater, consequently horn growth in male Spanish ibex ( Capra pyrenaica ) must compensate to minimize breakage. This is done by increasing the value of the second moment of the area at the base of horns, which keeps the maximum horn-bending stress low. Transverse horn ridges are apparently involved in helping to control the length of the lever arm, hence the bending moment, thus helping to minimize bending stress and torques about the occiput. In the rear-clash type of fight, the probability of horn breakage is highest, but horn-bending stress is minimized by clashing against the basal sections of horns. I hypothesize that the most frequent, and harmless, types of conventional fighting serve as reliable tests of the fighting ability of an animal. Contenders resist dangerous rear clashes by their body mass and absorb the energy of fighting and prevent skull rotation by contraction of their neck muscles.