Dog teams have a very special role in the world of search and rescue. The dogs' ultra-sensitive hearing, night vision, endurance and keen sense of smell have continually proven to be invaluable in the effort to locate missing persons. Because of their extraordinary abilities, dogs are often able to reduce the time spent searching, thereby increasing the chances that the mission persons will be found alive. A search dog's success stems from the fact that every human being has a smell -- not detectable by human beings, but discernible by animals -- which is caused by the constant stream of skin rafts and bacteria shed from the human body. How this scent is detected by the animals is dependent upon the training they have had in trailing or air scenting techniques. In both cases, the search dogs are able to locate missing persons even if they are hidden from view. Experts estimate that a single dog team can be as effective as 20 to 30 trained human searchers in locating a missing person in a given period of time.