Glass a lean deer with a thin neck and long legs, and you can bet he's a yearling or a 2½-year-old. Whitetails age like we do. The older they get, the thicker they get. As a buck turns 3½ and especially 4½ or 5½, his chest and sides bulk up and out and his neck swells and blends into his body. He looks like one of those blocky, muscle-bound lifters at your gym. If a deer is fortunate enough to survive to 6½ or 7½, he might get a sway back and lose his hips, just like an old horse.