All dogs track scent, even without training. You will notice your dog on your walks with his nose to the ground or in the air, sniffing away, zigging and zagging back and forth, following his nose. But training your dog to follow a scent, to perform a task, requires some training and direction on your part. The key to following a scent as a useful behavior lies in teaching your dog to be focused on one scent and follow it to its conclusion. This means ignoring other competing scents and following the scent trail over various terrain, for a significant distance. This is useful in tracking game, locating people, or participating in sanctioned competitions, where dogs follow a scent while on a 30-foot lead with a harness and follow a scent trail from 440 to 800 yards long. Some dogs follow scent trails with their nose to the ground, others catch scent in the air, and may vary their distance from the trail itself. In competition, as long a the dog stays within 30 yards of the trail and is on task, he is considered to be following the scent. Following a scent trail can be done indoors or outdoors, and it is easy to make this into a fun game for your dog. Even young puppies can be started learning how to follow a scent trail, although their focus may be limited and focusing on longer more complex trials will need to wait until the dog is a little more mature, around 1 to 3 years of age.