634 Scenting Signs
The scenting powers of dog have long attracted the attention of the scientists; Droscher in 1971 found that a barefooted man leaves roughly four billionths of a gram of "odorous sweat substance" with each step he takes. Budgett in 1933 found that water formed 99% of such a gram in the first place. In locating this minute sweat sample, the tracking dog has to overlook the accompanying, conflicting and much more powerful surrounding smells - animal, vegetable and mineral...and most men on the run wear shoes! The experiments of the Russian psychiatrists Klosovsky and Kosmarskaya on puppies led them to believe that the senses of smell and taste were so interconnected that they were virtually acting as one, and, could in general, act interchangeably.
I have noticed when using dogs on a trail that the dog's head is carried higher during morning tracking, perhaps because the air is rising bringing the scent with it. It is also noticeable that scenting ability varies from individual to individual dog within a pack, within a breed. The speed of a hound on a trail varies similarly, with accuracy not always sacrificed for pace. I suspect too that it is the determination and sheer persistence of the Bloodhound which makes it so effective at following cold trails, just as much as its scenting powers. Using Labradors, as tracker-dogs in the Malayan emergency, showed me that scenting prowess isn't enough by itself; you need a fanatical obsessive like a Bloodhound for really testing trails.
A dog's sense of smell is many many hundred times as powerful as ours. The reason for this lying in the fact that the areas inside a dog's nose which detect smells are roughly fourteen times larger than the equivalent areas in man. But a detector needs to be matched by a comparable performance in a receiver; the part of the dog's brain dealing with smell is proportionally larger and better developed than the human equivalent. One estimation gives a figure of forty times as many brain cells connected with the detection and perception of smell in the dog as in the human brain. The sheer sensitivity of the nose of dog allows it to specialise in hunting deer or fox, otter or hare, man or truffles and to locate avalanche victims, drugs, the wounded on the battlefield, explosives, temporary graves, dry rot, melanomas, the onset of epilepsy...even "moonshine" in America.
A German trainer of dogs for the police and then the army, Konrad Most, conducted experiments in the 1920s to determine whether dogs were using ground scents or individual scents on the trail. In one such test the tracklayer walked on foot for a while and was then carried roughly three feet above the ground for the remainder of the trail, on a suspended cable. Four highly experienced tracker dogs then attempted to track this trail. All four quite separately failed to track their quarry past the point where he left the ground. This, and other tests, supported the theory that dogs follow a scent based on disturbed ground scents. Different scents too initiate different resonses in individual dogs, not surprisingly. The ability to detect pheromones (chemicals produced by an individual that signal members of the same species) varies markedly too from one animal to another.
On the question of hounds hunting more than one quarry, as opposed to pursuing one scent only, Newton Rycroft wrote on this a few years ago. He argued that hounds will always have a favourite quarry, which may not be the huntsman's favourite quarry at any given moment. He recalled Ivester Lloyd's words on how in the old days the Welsh Foxhounds of the Ynysfor used to hunt fox, otter, hare and pine marten. But Rycroft himself preferred to use French hounds of wolf-hunting ancestry, believing that their skilful nose on the cold drag of a wolf would assist their descendants on a fox which had a long start before them, as can occur in Forest hunting. He pointed out, with characteristic good sense however, that "I cannot see what it profits a hound or pack of hounds to have inherited good noses if their huntsman has not the time, patience nor the sensitivity to allow them to develop these good noses to the full". Scenting skills need support! In Bloodhound trials it has been noted that the most successful hounds are those handled with the greatest rapport.
The tracking ability of the dog has been used to show that identical twins produce an identical odour. A dog can follow the trail of either twin after smelling an article belonging to one of them, although cases have been recorded of a gifted dog actually differentiating between the two. This tracking ability can be impaired by temperature change, rain, humidity, frost, wind, competing odours and the sheer passage of time. But no human or machine produced by man would get on such a trail in the first place. This tracking skill backed by dog's response to training is a valuable element in the unique man-dog partnership. Pigs employed to locate truffles usually eat them!
But to limit scenting powers just to the nose is not entirely correct. In his informative "The Mind of the Dog" (1958), RH Smythe recorded this information: "Now, odours, scents or smells represent the delights of paradise to every dog...it is well known that delicate smells make the mouth water. Saliva dissolves the scent-bearing vapours and so the dog not only smells them but also tastes them. It is believed that hounds use both smell and taste, especially when the scent becomes strong, and it is believed by many that when hounds 'give tongue' they are actually savouring the delightful odour as it dissolves in their saliva." In pursuit of this belief our ancestors utilised the "shallow flew'd hound" to hunt by sight and scent, in that order, as a "fleethound" and the "deep-mouthed hound" as a specialist scenthound.
There is a link too between well-developed sinuses and the ability to track. The best trailers have the skull-conformation to allow good sinus development, adequate width of nostril and good length of foreface so that there is sufficient surface between the nostrils to house the smell-sensitive lining membrane. Scenthounds, gundogs and other hunting dogs depend on the shape of their skulls for their acute smell-discrimination. In pedigree breeds, the wording of the description of the skull in the breed standard can therefore directly influence the scenting prowess of the dog. The narrower skull of the terrier leads it to prefer to hunt by sight, show less interest in following a trail of scent yet, through selective breeding, show enormous interest in scent coming from below ground.
No scientist has ever been able to explain satisfactorily the mysteries of scent in the hunting field. Scent is variously affected by the direction of the wind, heavy rain, freezing fog, high humidity, different crops, baking heat and the ground temperature. But no one has confidently stipulated the conditions needed for good scenting. Alington once observed that 'scent is almost certain to be good between 3.30 and 4.30 after a warm October day, when the thermometer suddenly drops to near freezing point.' He then hastened to add: 'Under no other conditions would the writer care to back his opinion that scent will be good'! Not a lot of value there then! No wonder the scientists stay away.