by Susan Ewing
When some people think of spring, they think of gardening and flowers. I think of getting lost in the woods and waiting for a Bloodhound to find me. I don’t really get lost, but I do wander into the woods of Allegany State Park, acting as a runner for participants in the National Police Bloodhound Association spring training seminar.
These week-long seminars offer handlers and their dogs the opportunity to sharpen their skills. The practice trails help the dog be a success so that he is always eager to search, even if the trail becomes difficult.
I go prepared, making the drive to the park with several socks stuffed into the waistband of my slacks, so that the dogs will have something to sniff before they find the trail.
The last time I acted as a runner, I did three different types of trail. First was a trail for Lula, a Bloodhound puppy. I took a clean sock from my waistband and shook it near Lulu’s nose, all the while talking to her in a happy voice. Then I dropped the sock and went a short way into the woods, making one sharp turn, and hiding behind a tree. It didn’t take Lulu long to find me, and I gave her a handful of treats as a reward, along with lots of praise.
Next I went out with another runner to lay a double trail. The two of us walked together, then split up. The dog would need to make the correct choice of which trail to follow. One dog was given my scent, and a second dog was given the scent of the other runner.
I wasn’t that far from the start of the trail and I could hear the dogs begin to bay as their harnesses were put on, the signal that they were going to work. A Bloodhound named Zoey soon found me and accepted several hot dog pieces and a scratch behind the ears.
The third trail I laid was for Missy, a young dog from Florida. Since this trail would be a bit more erratic, the instructor gave me a handful of blaze orange clothespins to clip to random branches. This would let the handlers know whether or not they were on the right trail. Soon enough Missy tracked me down, ending a successful exercise.
All these dogs were following “scent rafts” that drifted down from my body. Dying cells are shed from a human at an average of about 40,000 cells per minute. What a hound smells is the gas given off as bacteria work to decompose these cells. The rafts are carried down and out by the layer of air that surrounds every human.
This air is warmer and less dense than surrounding air and it creates a current that travels up the body from the feet, ending about 18 inches above the head. As the current rises, it picks up rafts of dead cells and releases them above the head. The rafts drift back and away and fall to the ground Bacteria work on these rafts, producing a scent trail. The speed at which the bacteria will act on the cells is affected by temperature, humidity and wind. It is harder for a hound to follow a trail on a hot, dry, windy day than on a cooler day with a light rain falling. Moisture is needed for the bacterial action.
That moisture component is one of the things that makes Bloodhounds so efficient. They drool. All that saliva helps activate the scent. The tips of their ears are generally also wet from the saliva, and as they frame the face, they help funnel the scent towards the nose. All that loose skin tends to fall forward as a dog trails, and that, too, helps gather the scent and push it toward the dog’s sensitive nose.
Dog noses are built to gather and identify different scents. Dogs don’t get “scent fatigue”. A scent is just as strong for a dog an hour later as it was when it first smelled it. The human nose tends to “get tired.” A scent we find strong and noticeable at first tends to be less evident the more we smell it.
Then there are the cilia, the tiny hair-like extensions in the lining of the nose. These gather the scent. There are 6 to 8 cilia per inch in humans and 100 to 150 per inch in dogs. The more air breathed in, the more scent gathered. Humans take in about 1.6 cubic inches of air in a breath; dogs take in 6 cubic inches or more.
Dogs also beat humans in the count of scent receptors per square inch in the nose. There are 5 to 20 million scent receptors per square inch in man, and 220 million per square inch on average in dogs.
It’s winter now, but I look forward to getting lost again this spring.