I've recently spent some time in Zambia around a great number of this species of hartebeest. Upon my observations I found one bull in particular that really stood out to me. He was the only one with this dark strip down his face and he had heavy and worn horns as well as a big knot on his forehead... all others I have seen in the field and mounted in taxidermy shops did not. Is this an uncommon trait or an indication of age? He was with a small group but tended to hang by himself on the outskirts of the small group.