Tracking is a technique in which dogs are trained to locate certain objects by using the object's scent, for a variety of purposes. Tracking has always been an essential skill for dogs to survive in the wild, through hunting and tracking down potential prey. One of the main disciplines used in Working Trials. Primarily, dogs use their sense of smell, to find and follow a track. Dogs have a highly sensitive olfactory system superior to humans and are able to discriminate between different human's scents amongst the ground disturbance. There are several uses for tracking. Several examples include: Tracking in police work as Police dogs. Tracking tasks may include tracking down alive and dead individuals, recovering evidence from a crime scene, finding explosives, drugs, and in arson investigations. Tracking for search and rescuing as search and rescue dogs. Tracking dogs are used to find individuals trapped in avalanches or disaster zones. Tracking in hunting to recover animals shot down by hunters. Tracking as a dog sport, such as in tracking competitions using tracking trails.