Playing Deer Games

Tonight I was entertained for about a half hour watching deer frolic in my back yard. There were seven of them but only three were frolicing - playing deer games. The game involved rubbing heads. The deer would approach each other with the forehead pointing ahead and aiming at the other deer's head. They would grind the tops of their heads together and push against each other until one crumpled, turned or fell down. Sometimes all three deer would push their heads together forming a 12 legged tripod. Why would deer do this? They looked like they were playing. They would get all frisky like Rudolph and his friends in that Christmas special with the Burl Ives snowman riding on a electric razor, the abomidable snowman and the misfit dentist. Maybe it was a game. Maybe they had headaches and were trying to relieve them. Maybe they were marking each other as friends - rubbing the scent glands on each other like cats do to their favorite humans. I don't really understand what they were doing but it was fun to watch.