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| Author Dan Ellison with Hunter after a successful shoot |
By Dan Ellison, former narcotics dog handler, California.
IT is early morning on the first day of duck season, May 1, and the temperature is a cool 6degC. You pack up a lunch and water for you and your dog because you know that by noon you will be looking for the nearest rest area.
The wind soon blows a little faster than it has in past weeks and you wonder why your dog is working so poorly on retrieving the ducks that have fallen. You have kept him in great shape and he receives only the best food and training ... what is the problem?
The answer is - his tracking ability.
Tracking the scent of an evasive prey can be a difficult and trying endeavour at times. We wonder why sometimes our dog tracks its prey well and at other times it seems he doesn't even know another animal has been in the area.
The dog's ability to find a scent is 10 to 20 times greater than ours, which sounds like a case of the blind leading the seeing during hunting trips. With his sense of smell being so much greater than ours it's a wonder we don't make more mistakes with our dogs when we, as those without scenting ability, presume to train those who have all the ability.
If you follow some basic rules of scent, the wondering and guesswork can be reduced. The first rule of thumb is that scent is greatly reduced by sunlight. Scent that is laid in direct sunlight will last only about two to five hours. Sunlight deodorises scent with its ultra-violet rays. It also increases the Earth's temperature causing the Earth to exhale. When Earth exhales (heat rises) the scent is lifted to such a degree that it rises off the face of the earth and is then airborne.
Compare this scent to the one laid at night. It is known that a scent laid at night will be detectable for 10 times the amount of time as that laid in sunlight. Not only are there no ultra-violet rays at night for obvious reasons, but the Earth is also cooler than during the day, causing it to inhale scent which keeps it on or near the ground. There are other factors that greatly reduce the amount of detectable scent. With any change in the climate, you get more dust flying and a dissipated scent trail.
Experiments have proved that the Earth breathes. When it is hot the Earth exhales and when it is cold the Earth inhales. An example of the Earth exhaling is seen very readily when we drive down the street on a summer day. When we look ahead we think we see water on the road but it is commonly known as a mirage. The Earth is exhaling and along with its gasses and air is moisture from the ground. Moisture is the number one best conductor of scent.
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| Californian hunting dogs Aaron (right) and Angel (NZ-bred) with their trainer. |
Moisture holds scent like a battery holds an electric charge. Without water the quality of scent is lost very quickly ... as happened on that first windy day of the duck season.
Television has often misled the public with its stories incorporating prisoners escaping from the bloodhounds after breaking out of prison. The first mistake the convict usually makes is to jump into a stream and run down it in the hope of throwing the dogs off his scent.
Water retains scent. The scent from the man could possibly dissipate in the water, depending upon how fast the stream was moving, but as with strong winds the scent would spread out along the banks of the stream, clinging there until the sun came out and deodorised it. No dog, including the bloodhound, can track a man after five hours of direct sunlight unless he has learned to follow the track of crushed foliage or other additional scents independent of the natural and distinctive order of the quarry (object of the chase).
The scent of foliage is not greatly affected by sunlight. But hard, falling rain will obliterate this scent. All considered, the ideal conditions for a prison break would be during heavy rain with high winds, or alternatively a very hot day with dry soil and high winds.
A high wind causes eddy-currents and makes scent conditions uncertain at times. The high winds dissipate the scent just like moving water can. A good narcotics dog handler knows to turn off the fans of a room before he does his search, to reduce the amount of dissipating scent throughout the room. The best conditions to track a pig or deer are up-wind, when the Earth is warm and the air is cool, and a little dew on the ground wouldn't hurt either.
Scent oil from an animal is the main chemical that the dog is detecting. The oil derives its individual odour from the body's fatty acids of which isovalerianic and propanoic give out the most lasting smells. Sweat consists of about 99 percent water and one percent fatty acids containing the scent. Remember that this combination of water and fatty acid will evaporate after only five hours of exposure to sunlight.
Most animals (including man) lose up to one kilogram of sweat every 24 hours. Some of this scent is caught in our clothes and some drops to the ground along with skin cells, hair and other body matter. These scents are then taken into the nose and enter the openings in the olfactory gland.
There are two theories regarding the way the gland sends message to the brain about a specific scent. One is that each opening in the gland is only large enough to allow entry of a certain sized molecule, which translates in the brain to a specific scent; and the other theory is that the openings in the glands allow a series of molecules into several openings at the same time, collecting many pieces of information about a certain scent to be sent to the brain and collated for evaluation and conclusion.
It is possible for the olfactory gland to become over-saturated with a scent so that the brain does not detect any scent at all. This is commonly known as nasal fatigue. It is possible to have so much of one scent that the dog does not detect what he has been trained to detect. I don't know if this has ever happened in the field, or if hunters would keep a record of the event if it did happen, but if you do come across it ... it IS possible. As a narcotics dog handler I have personally experienced this with one of my own dogs in a room full of marijuana.
I hope that by understanding how scent works we, as dog trainers and hunters with dogs, will be able to break down our training areas so that the dog can best be evaluated according to ability, and so that we know enough to make allowances where unusual conditions may be affecting a good tracking dog's ability. A bad day's hunting may simply be caused by Mother Nature's routine cleansing of her world.
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