I have done some research, but I can’t find an answer to a basic question.
Let’s say I am wanted by the police, and they know that I headed into the woods at a certain point less than 24 hours ago. I am fully dressed, including gloves, and since I know they are looking for me I decide to zig zag my way deep into the woods in hopes of not being found.
The police show up with their dogs, and let’s say they even have some clothing I have worn recently. The dogs sniff the clothing and off they go looking for my ‘trail’. That’s where I don’t understand. A human can observe the surroundings and determine where I went perhaps based on footprints, broken branches etc. But the dogs are apparently able to follow my scent for miles.
I realize that dogs have incredible noses and can smell things far better than we can, but our eyesight is better and we understand clues that dogs can’t comprehend.
So what exactly am I leaving a trail of as I walk through the woods? Is it my smell or the disturbance of the dirt? Do my shoes give off a powerful smell that a dog can easily pick up? Does a foot print leave that scent with every step I take? I know that one way to trick a dog is to walk in a stream since they obviously loose the scent in the water.
So what is it exactly that the dogs are tracking as I walk through the woods?
Dog’s mostly don’t follow the smell of your footprints.
You are constantly shedding body dander, hairs, and your breath and sweat condense or are absorbed on stuff around you. This leaves a trail that the dog’s nose can follow. If you are in a narrow stream, it is likely that you will leave enough of this on the banks for a dog with a good nose to track you.
You know when you enter a hotel room if it was recently, or even not so recently, smoked in. You might be able to tell if it was cigarette of pipe/cigar smoke. For a dog, they know if a person was in the room, and any of them were one who’s smell they know. Like the smoker, our smelly stuff is spewing off constantly, and landing on anything nearby.
Also the surface of the ground gets sort of a crust where all the smelly stuff mostly cooks off. When you disturb the ground, you are leaving a trail of smells from deeper in the ground. So even if you are wearing a bio-hazard suit, there is a chance of you being tracked by your stir-trail.
Is there currently any way to collect DNA from any of this? Let’s say we know you went into the woods at point X twenty-two hours ago, but we don’t know your identity. Can dogs point out individual human hairs to us, or in some way indicate to us that “some shed epithelial tissue landed on this leaf right here. Get it to the lab”?
I get it that if you occupy a room for a longish period of time that your body dander, dead skin cells and hair are left around and would provide clues to a dog that you were there. It’s a confined space. But if I am running through the forest the amount of ‘residue’ I am shedding would be relatively small, and fleeting, since the wind and moisture in the air would tend to distribute it over a fairly wide area. For a dog to stay on my trail they would have to detect extremely small amounts of residue over a large area.
Obviously dogs can do it, it just seems incredibly hard and untrustworthy…
Human trackers skilled enough to follow someones trail are hard to come by, and depending on the terrain and conditions it may impossible to pick up and clear signs that a person has passed through. It’s even worse in some place where people frequent, there will be footprints, and broken branches everywhere. But dogs bred to track will do a fantastic job picking up your scent. They can pick it up off the ground where you’ve stepped, off anything you touch, and out of the air if you’ve got a few dead skin cells still floating around. Dogs aren’t perfect, but a far sight better than most any human.
I had a trial where my client was tracked by a police dog, so I learned a bit about it. Apparently, a dog can smell 10,000 times better than a human. And a scared fleeing human will generate a bit more of “extremely small amounts of residue.” The fact that the dog found a particular person wouldn’t be evidence, necessarily. Often, they know who they are looking for, and just need the dog to track you down. (it might be probable cause to detain and question you). They would still need non-canine evidence to actually convict you. In other words, a guy shoots his family and runs into the woods behind the house. The police know he’s hiding there somewhere. The dog finds him.
I had heard <no cite> that a dogs sense of smell is as powerful a tool as our sight. That they can discriminate smells like we can colors. To a dog, tracking is like us being able to keep our car between the lines as we drive. Some roads have very faded lines but we can still make a “best guess” about where the lanes are by other clues. Even without a road we recognize 2 lines of missing vegetation as the path many vehicles have taken before.
I have volunteered to be a “victim” for search and rescue K-9 training and believe me, what dogs do with their noses is hard for humans to grasp. They can easily find you if you are buried deep in rubble, or covered with brush and leaves. They barely seem to need to look for you.
I’ve observed my own dogs strike a scent, cast around, and in a few seconds they will figure the direction of the animal’s path – I believe this is based on the age of the scent – each footprint has a different age to it. Some talented dogs can track car tires this way, although it is much harder.
I have one dog who, on the command “Find it!” will begin to cast around for a trail, and will find and bring back anything with my scent on it, or with some “out of place” feeling to it (i.e. someone else’s lost hat). If I say “Look back”, which is the traditional herding command for what is called a ‘blind gather’, she will scent for lost or hidden livestock, find them, and bring them to me. Believe me I do not know how she does this, but she is quite reliable, and it is not a particularly unusual skill in herding-bred dogs.
This same dog, when she was about a year old, rescued us on a hiking trip in the Sierras when we were crossing a bare granite slab some acreage in extent and lost the path entirely – it was marked by little cairns but once you were off the trail they all just looked like random rocks. We looked for the trail for more than an hour and finally I said wearily, not even meaning anything by it, Oh, Bonnie, please, let’s go home. She immediately ran across the granite to the beginning of the trail back to base camp through the woods and looked back at me, like “why didn’t you tell what you were looking for?” For her, the whole path across the granite slab, invisible to human beings, was probably like neon paint.
Yep. If I come into work 10 minutes after a gal wearing too much perfume arrived I can track the scent through the halls all the way to her desk.
If dogs can do this x10,000 they should have no problem hours later outdoors.
Reminds me also of a time I was deer hunting. I walked a straight line path to my tree and climbed up onto the tree stand. A couple hours later a deer came strolling by and stopped on a dime when she hit the line I had walked 2 hours previous. Head went down and ears perked up immediately.
And the same is also true for dolphins, and what they can do with their bio-sonar. It’s said that a dolphin can find a dime buried in the mud. IIRC, I read this in Lads Before The Wind by Karen Pryor, her memoir of her years as a dolphin trainer at Sea Life Park, Hawaii. They did research there as well as public entertainment dolphin shows, and they used trained dolphins as assistants in some underwater open-ocean work.
Just recently watched a show on cable (Mexican Drug Wars, I think) in which a trained ‘drug’ dog sniffed out a load of drugs that was sealed inside of a metal container that was then sealed inside of a fuel tank full of fuel. Supposedly, the dog was able to smell the scent of the drugs even though they were sealed inside of a container that was immersed in fuel. I guess it’s possible that there were trace amounts of the drugs scent on the outside of the container, but it was still an impressive display of a dogs sense of smell.
The dog probably detected poor quality control on the smugglers part rather than the smell of the drugs coming through the fuel. The guys putting the drugs in the first container had residue on their hands and clothes and general environment and contaminated the outer container. It is really difficult to get things clean to the point that a trained dog cannot detect them.
I’ve read that they can identify different kinds of materials using only sonar.
Yes, I believe they perceive scent not only as identity and direction, but time. A dog knows not only who the scent belongs to, and what direction that person went, but also how long ago, and other things that happened before or after that. Not to mention having some clue as to the target person’s emotional state, and maybe even their health.
A huge area of a dog’s brain is dedicated to scent interpretation; they don’t just detect it, they analyze it. They also have a “vomeronasal organ,” a scent-analyzing organ (probably for pheromones) that humans are not believed to share. It’s hard to imagine what their perceptual world must be like.
There are a number of books going into depth about (our best understanding of) how dogs perceive the world. This was one of the most surprising things I recall from one of them - when confronted with a scent trail, they can tell which direction is older, therby telling which direction to follow.
An analogy - as others have suggested - is to think of their sense of smell as important to them as our vision is to us.
I recall the one book going into considerable length about what factors affect a dog’s ability to track. I seem to recall rain significantly decreases the time in which a trail becomes untrackable. There are a number of amazing instances, but in the more run-of-the-mill situations, there are significant limits affecting success.
With drug dogs, there is also the considerable likelihood of false positives - responding to handlers’ cues or for other reasons. Saw a cop taking a dog around a stopped car a week or so ago. That guy was doing all kinds of things to get that dog to respond, but to the dog’s credit he wouldn’t. (No, I’m not a fan of current stop and search laws/practice in the US.)
Just my opinion, but I found that one of the least satisfying of the several books on the subject I have read. It was far lighter on the science than I had expected from the reviews I had read. This author’s tone was more emotional/subjective than I expercted/desired, often coming close to eulogizing and anthropomorphizing dogs she had known and loved in the past.
