Is horn length crucial for Alpine chamois?

Animal weapons are one of the most studied morphological traits, particularly in Artiodactyla. Since in polygynous species males with larger weapons tend to be more successful in gaining access to females, researchers have traditionally focused on horn size. However, in species with limited horn size, weapon size has been assumed to have a reduced or null effect on life history traits. We examined the effect of intrinsic and extrinsic factors on the length of the second and third segments of Alpine chamois horns (Rupicapra rupicapra) in a population living in a poor environment. Our aim was to test how environmental conditions affected weapon growth and whether compensatory growth occurred. We showed that horn length was isometric to body size, although male horns grew more quickly. Ecological factors such as snow and forage availability affected weapon length, though mildly. No sign of compensatory growth was detected. We inferred that chamois mainly use horns as armament in intrasexual interactions. However, horn length was not a key element since horn growth remained isometric, at least under suboptimal ecological conditions. In species without extreme weapons, the handicap caused by longer horns is likely not compensated by an increase in individual fitness.