An impala herd consists of does and fawns and a dominant buck.  He's the one on the left with the long horns.  During the breeding season he's mighty busy protecting his ladies from the attentions of amorous bachelors.   Meanwhile, the bachelors practice sparring with each other, working toward the day when they feel prepared to challenge a dominant male's right to control the herd.  I was surprised to learn that baboons will sometimes infiltrate an impala herd and attempt to catch, kill and eat young impalas.