Internal architecture of pampas deer antlers differs in males allocated with and without females

Bone mineralization of antlers and the depth of the antler seal (the basal surface of the cast antlers) are positively related to testosterone concentrations. Pampas deer males that are in permanent contact with females have greater, heavier, and darker antlers than males that are isolated from them. The objectives were to determine if antler compact/spongy bone ratio, antler seal depth, and compact bone darkness are greater in pampas deer males permanently allocated with females than those in males isolated from them. Antlers from males permanently allocated with or without females were cut transversally in seven points and scanned, and the compact/spongy ratio was calculated. The pixel intensity of each image was determined with a software for image analysis. The coronet of the antler was cut longitudinally, and the height of the most prominent protrusion was measured. The compact/spongy ratio was greater in antlers from males that were in contact with females in the second tine (P?=?0.02) and tended to be great in the two other tines (P?=?0.06 and P?=?0.1, respectively). Compact bone pixel color was darker in males in contact with females than that in males isolated from females in two points (P?=?0.02 and P?=?0.05, respectively) and tended to do so in two more (P?=?0.055 and P?=?0.1, respectively). Antler seal convexity was also greater in antlers from males in contact with females (P?=?0.006). We concluded that permanent contact with females stimulated pampas deer males increasing compact bone portion of the antler tines, the seal depth size, and the darkness of the compact bone.