“Houzeau relates that, while crossing a wide and arid plain in Texas, his two dogs suffered greatly from thirst, and that between thirty and forty times they rushed down the hollows to search for water. These hollows were not valleys, and there were no trees in them, or any other difference in the vegetation; and as they were absolutely dry, there could have been no smell of damp earth. The dogs behaved as if they knew that a dip in the ground offered them the best chance of finding water, and Houzeau has often witnessed the same behaviour in other animals.”
I have myself frequently observed this association of ideas between hollow ground and probability of finding water in the case of setter-dogs, which require much water while working; and it is evident that the ideas associated are of a character highly generic.
Further, Mr. Darwin writes:—“I have seen, as I dare say have others, that when a small object is thrown on the ground beyond the reach of one of the elephants in the Zoological Gardens, he blows through his trunk on the ground beyond the object, so that the current reflected on all sides may drive the object within his reach. Again, a well-known ethnologist, Mr. Westropp, informs me that he observed in Vienna a bear deliberately making with his paw a current in some water, which was close to the bars of his cage, so as to draw a piece of floating bread within his reach.”[38]
In Animal Intelligence it will be seen that both these observations are independently confirmed by letters which I have received from correspondents; so that the facts must be accepted. And they imply a faculty of forming generic ideas of a high order of complexity. Indeed, these are not unlike the generic ideas of intelligent water-dogs with reference to water-currents, which induce the animals to make allowance for the force of the current by running in the opposite direction to its flow before entering the water. Dogs accustomed to tidal rivers, or to swimming in the sea, acquire a still further generic idea of uncertainty as to the direction of the flow at any given time; and therefore some of the more intelligent of these dogs first ascertain the direction in which the tide is running by placing their fore-paws in the stream, and then proceed to make their allowance for driftway accordingly.[39]
Lastly, Mr. Darwin writes:—“When I say to my terrier in an eager voice (and I have made the trial many times), ‘Hi, hi, where is it?’ she at once takes it as a sign that something is to be hunted, and generally first looks quickly all around, and then rushes into the nearest thicket, to scout for any game, but finding nothing, she looks up into any neighbouring tree for a squirrel. Now, do not these actions clearly show that she had in her mind a general idea, or concept, that some animal is to be discovered and hunted?”[40]
From the many instances which I have already given in Animal Intelligence of the high receptual capabilities of ants, it will here be sufficient to re-state the following, which is quoted from Mr. Belt, whose competency as an observer no one can dispute.
“A nest was made near one of our tramways, and to get to the trees the ants had to cross the rails, over which the waggons were continually passing and re-passing. Every time they came along a number of ants were crushed to death. They persevered in crossing for some time, but at last set to work and tunnelled underneath each rail. One day, when the waggons were not running, I stopped up the tunnels with stones; but although great numbers carrying leaves were thus cut off from the nest, they would not cross the rails, but set to work making fresh tunnels underneath them.”
These facts cannot be ascribed to “instinct,” seeing that tram-cars could not have been objects of previous experience to the ancestors of the ants; and therefore the degree of receptual intelligence, or “practical inference,” which was displayed is highly remarkable. Clearly, the insects must have appreciated the nature of these repeated catastrophes, and correctly reasoned out the only way by which they could be avoided.
As this is an important branch of my subject, I will add a few more illustrations drawn from vertebrated animals, beginning with some from the writings of Leroy, who had more opportunity than most men of studying the habits of animals in a state of nature.[41]