The greyhound courses by sight, but all other dogs hunt by scent, and the speed and certainty of foxhounds in full cry bear a new significance when we recollect that it is scent that is directing them. Could vision be any more swift and sure?
We may heartily wish, as a child once remarked to a friend of mine, that Rover had a prettier way of saying “How d’ye do?” to his canine friends. But that and other even more objectionable habits do not prevent his entrée into the most exclusive circles of human society. He is taken at his own valuation, and that, to be sure, is considerable. But the minute, the meticulous, olfactory scrutiny he makes of other dogs is but one more example of the predominance of this sense in his brain. (See also later.)
When you take him for a walk also, how busy his nose makes him! Burrowing here and there among the grass and undergrowth, picking up an interesting trail that leads him a little way, until it crosses another, fresher, perhaps, or more interesting, that has to be taken up—here a cat’s, there a rat’s, further on a rabbit’s, and then, with short squeals, scrapings in the ground, and buryings of his muzzle, a weasel’s!—the whole intermixed and intermingled with whiffs of something like old decayed bones, or of another and an unfriendly dog, or of some ardent lady-love who has passed this way but shortly since!—is not this a richer, a fuller, a more attractive, world than ours, with its fickle sunlight, its pallid greys, its mournful purples, its unattainable horizon-blue? For our life is primarily one of vision.
I am sure his dreams, also, are compounded of the gorgeous odours of some other world, such odours as even our woods in autumn know nothing of.
But we must return again to science and Fabre. This time we shall accompany him on an excursion with the wonderful dog who is trained to discover for the gourmet the truffles that are growing deep in the soil.
Left to his own devices, we learn, the truffle-hunting dog indicates the position not only of truffles, but also of all manner of hypogean (underground) fungi, “the large and the small, the fresh and the putrid, the scented and the unscented, the fragrant and the stinking.” Only, he never at any time indicates the presence of the ordinary mushroom, not even while it is still underground, before it sprouts up as the fungus we know. And yet to our nostrils the mushroom has the same smell as many of the hypogean fungi he does indicate. Consequently, therefore, the dog is not guided to the deep fungi by what may be called the general odour common to all fungi. He must be able, that is to say, to distinguish the hypogean varieties by some quality which is not odour, or, at least, not odour as we understand it.
There is, as it happens, something like a truffle-hunter among the insects also, what is known as the Bolboceros beetle. This little creature feeds on the hydnocystis arenaria, a hypogean fungus. Fabre, having captured some of these insects, placed them on earth in which he had buried the fungus at depths of six or seven inches. It was found that the beetles, without making any trial bores, sank vertical shafts through the soil direct to their food.
We may insert here also, as bearing upon the problem which is now emerging into clearness, an observation and a suggestion similar, as we shall see, to that of Fabre, on the badger by Mr. Douglas Gordon (Spectator, August 6th, 1921):
“The real damage wrought by the badger is microscopic. His diet mainly consists of roots, green herbs, mice, frogs, and insects. Like the fox, he has a great partiality for whorts and blackberries when in season, and he is particularly fond of grubs. For the sake of these he will dig out every wasp’s nest he can find. A considerable number of rabbit ‘stops’ also fall to his share, and in unearthing the latter he practises a somewhat remarkable piece of woodcraft. The hole which contains the nest may run to the depth of several feet, and the nest itself be situated ten feet from any entrance, but this does not trouble the badger. He makes no attempt to follow the tortuous passage, as a man when digging would be obliged to do. His unerring nose locates the exact spot where the young rabbits lie, and from the most convenient point he bores for them. Should it be a ‘ground-burrow,’ he sinks a vertical shaft. In the case of a steep bank he drives a horizontal tunnel, and, shallow or deep, with unvarying accuracy.
“Not long ago I saw a striking case of this on Haldon Hill, near Exeter. The burrow opened on to a little gully, and ran back some distance under the heath. At least five paces from the nearest hole was the badger’s freshly cut shaft, about three feet deep, and around it were littered the ruins of the nest—the little tale of bloodstained fur so eloquent of tragedy. There on the earth drawn from the shaft the raider’s spoor was plain enough, but no imprint of his pads could I find upon the impressionable mould anywhere near the holes. This meant that he must have found the nest while traversing the heather—sensed it beneath him, in fact. And here an interesting point arises. What sense did he employ? Could he possibly ‘smell’ the rabbits through three feet of packed mould? Earth is a potent deodoriser. Do certain animals possess a sixth sense—a sympathy something akin to that of the divining rod? If so, this goes farther to explain the much-discussed principle of scent than anything yet suggested.”
Is this sense, then, as we see it in operation in the badger, in the truffle-hunting dog, in the Bolboceros beetle, and still more wonderfully in the Peacock and Banded Monk moths, drawn to their mates “from the edge of the horizon,” and, it may be, against the wind—is this sense the same as our own sense of olfaction, only much more acute? Fabre finds some difficulty in believing that it can really be the same. “Odour,” he argues, “is molecular diffusion.” But nothing material, nothing our senses can perceive, is emitted by these moths, and yet they can summon their mates from relatively enormous distances. However fine may be the divisibility of matter, Fabre’s mind refuses to entertain the suggestion that this far-flung summons is addressed to a sense of smell of the same nature as ours. It would be tantamount, he says, “to reddening a lake with an atom of carmine, to filling immensity with nothing.”