But now there is a new kind of job that dogs do, and it is called Historical Human Remains Detection (HHRD). This job is so new and so specialized that only about 18 dogs in the whole world have been certified so far to do it. The difference between an HRD dog and an HHRD dog is that the first kind of dog is looking for residual scent, small scent sources, and old cases where maybe a body has been buried or hidden for a few months or years. The HRD dogs learn to ignore any kind of fresh human scent or any animal scent.
The historical human remains detection dog, however, is trying to find where human bodies decomposed a really long time ago, like 100 years or even more. Another name for these dogs is historical grave detection dogs. Sometimes the grave is so old that there are only tiny fragments of the body, but what the dog is detecting is the odor of decomposition that was left in the soil when a body used to be there.
I would just like to mention, at this point, that the human nose has about 5 million olfactory cells, and the canine nose has about 220 million. Also, almost one-eighth of the brain of a dog is devoted to processing olfactory input. Everyone, dog and human, should remember this very important information because it explains why dogs are able to do some of the spectacular things they do, such as finding 100-year old grave sites.
Dogs can be trained to do different types of scent work, but they work in different ways according to the job they are doing. A dog who is sniffing the air for the scent of a live human will hold his head up. But a dog who is looking for old graves, old bone, and teeth will work slowly, with its nose close to the ground because these types of scents tend to be found only on the surface of ground and not in the air.
The best conditions for working a detection dog are temperatures between 40ºF and 75ºF, with moist ground, high humidity, and a light breeze. Dogs can work in more extreme conditions such as high heat or snow, but the working time will be decreased. Prehistoric graves are the most fragile and difficult scents for dogs to find, so the dogs need frequent rest and water breaks.
|Legend, a Belgian Malinois trained as an HHRD dog.|
It can take as long as two or three years to train dogs for this type of work. Many of them start training as puppies, imprinting on the scent of human bones at a very young age. The best dogs for the job seem to be those with longer noses, because that means they have lots of smell receptors. Also, they have to have a strong work ethic and a huge desire to please. The Institute for Canine Forensics, in Woodside, California, trains many dogs for HHRD work.
Detection dogs are trained by rewarding them for finding the right types of remains. They learn to "alert" by sitting or lying down when they find the scent. They are taught to ignore anything else, such as animal remains. As training goes on, the job of finding the human remains is made more difficult until the dog alerts even on very small amounts or fragments, such as a tooth or bit of bone. The HHRD dogs, just like HRD dogs, are taught never to pick up or dig up the remains. Everything has to be preserved just the way it was found.
HHRD dogs learn to work an area with a handler, in a methodic grid pattern. Humans sometimes think that remains and artifacts must be in a certain location, but dogs don't know that, so they are free to figure out where these items really are, just by using their sense of smell.
So once again, dogs have proven themselves to be extremely clever and useful to people. Probably, we will see more and more HHRD dogs in use in the future. However, we will probably not see chihuahuas doing this job because (1) a lot of chihuahuas have short noses, and (2) not many chis are so eager to please that they will go out in all kinds of weather to sniff around all over the ground for people who have been dead for centuries already!