Not all SAR dogs perform the same type of search. Some dogs are tracking (or trailing) dogs, and others are air-scent (or area-search) dogs. The types overlap, but the distinction between the two guides are the training process and how the dog participates in missions. Tracking dogs work with their nose to the ground. They follow a trail of human scent -- typically heavy skin particles that fall quickly to the ground or onto bushes -- through any type of terrain. These dogs are not searching, they're following: Tracking dogs need a "last seen" starting point, an article with the person's scent on it to work from and an uncontaminated trail.
For tracking, time is an issue. If a child disappears from a school playground or a inmate escapes from a prison, a tracking dog might be called in to follow the person's scent immediately after the disappearance, before other search groups and law-enforcement personnel contaminate the scent trail.
Air-scent dogs, on the other hand, work with their nose in the air. They pick up human scent anywhere in the vicinity -- they don't need a "last seen" starting point, an article to work from or a scent trail, and time is not an issue. Whereas tracking dogs follow a particular scent trail, air-scent dogs pick up a scent carried in air currents and seek out its origin -- the point of greatest concentration.
Air-scent dogs might be called in to find a missing hiker located "somewhere in a national park," an avalanche victim beneath 15 feet of snow or people buried under a collapsed building. Air-scenters might specialize in a particular type of search, such as:
- Cadaver - Dogs specifically search for the scent of human remains, detecting the smell of human decomposition gasses in addition to skin rafts. Cadaver dogs can find something as small as a human tooth or a single drop of blood.
- Water - Dogs search for drowning victims by boat. When a body is under water, skin particles and gases rise to the surface, so dogs can smell a body even when it's completely immersed. Due to the movement of water currents, dogs can seldom pinpoint the exact location of the body. Typically, more than one SAR team searches the area of interest, and divers use each dog's alert point, along with water-current analysis, to estimate the most likely location of the body.
- Avalanche - Dogs search for the scent of human beings buried beneath up to 15 feet of snow. Photo courtesy 911BC K9 Search and Rescue
- Urban disaster - The most difficult SAR specialty, urban disaster dogs search for human survivors in collapsed buildings. They must navigate dangerous, unstable terrain.
- Wilderness - Dogs search for human scent in a wilderness setting.
- Evidence/article - Dogs search for items that have human scent on them.
Cadaver and water-search dogs are the only types specifically trained to scent for human remains, although all SAR dogs will alert to remains if they find them. In major disasters like the Oklahoma City bombing in 1995, the collapse of the World Trade Center in 2001 and the 2005 earthquake in Pakistan, air-scent dogs in all specialty areas assisted in the search for survivors. This actually led to problems for some of the dogs, because SAR dogs trained to find living people can become discouraged when they find only dead bodies. The dogs understand that live finds are preferable, partly due to their training, partly due to the reactions of their handler and partly because live people can usually give some form of feedback -- and the dogs crave feedback. At Oklahoma City and Ground Zero, handlers and firefighters hid in the rubble to give the dogs a living person to find so they could feel successful and get their reward.
In urban disasters, where people are trapped beneath precarious piles of debris, a dog's strength, confidence and agility are key. Even more important, though, is obedience: An out-of-control dog is a liability in search situations. This is where SAR standards come in.