Most interesting of all was their method of hunting under water. They came swimming along with an erratic course, darting a foot or so forward very swiftly in a straight line, then starting to gyrate in looped turns at reduced speed. While swimming straight and swiftly their whiskers were, as far as I could see, laid flat against their head, but while circling they were erect and bristled out in all directions, as they sought contact with some prey. I have no reason to believe that vision plays any part in the water-shrew’s hunting, except perhaps in the activation of its tactile search. My shrews may have noticed visually the presence of the live tadpoles or little fishes which I put in the tank, but in the actual hunting of its prey the animal is exclusively guided by its sense of touch, located in the wide-spreading whiskers on its snout. Certain small free- swimming species of cat-fish find their prey by exactly the same method. When these fishes swim fast and straight, the long feelers on their snout are depressed but, like the shrew’s whiskers, are stiffly spread out when the fish becomes conscious of the proximity of potential prey; like the shrew, the fish then begins to gyrate blindly in order to establish contact with its prey. It may not even be necessary for the water-shrew actually to touch its prey with one of its whiskers. Perhaps, at very close range, the water vibration caused by the movements of a small fish, a tadpole or a water-insect is perceptible by those sensitive tactile organs. It is quite impossible to determine this question by mere observation, for the action is much too quick for the human eye. There is a quick turn and a snap and the shrew is already paddling shorewards with a wriggling creature in its maw.
In relation to its size, the water-shrew is perhaps the most terrible predator of all vertebrate animals, and it can even vie with the invertebrates, including the murderous Dytiscus larva described in the third chapter of this book. It has been reported by A. E. Brehm that water-shrews have killed fish more than sixty times heavier than themselves by biting out their eyes and brain. This happened only when the fish were confined in containers with no room for escape. The same story has been told to me by fishermen on Lake Neusiedel, who could not possibly have heard Brehm’s report. I once offered to my shrews a large edible frog. I never did it again, nor could I bear to see out to its end the cruel scene that ensued. One of the shrews encountered the frog in the basin and instantly gave chase, repeatedly seizing hold of the creature’s legs; although it was kicked off again it did not cease in its attack and finally, the frog, in desperation, jumped out of the water and on to one of the tables, where several shrews raced to the pursuer’s assistance and buried their teeth in the legs and hindquarters of the wretched frog. And now, horribly, they began to eat the frog alive, beginning just where each one of them happened to have hold of it; the poor frog croaked heartrendingly, as the jaws of the shrews munched audibly in chorus. I need hardly be blamed for bringing this experiment to an abrupt and agitated end and putting the lacerated frog out of its misery. I never offered the shrews large prey again but only such as would be killed at the first bite or two. Nature can be very cruel indeed; it is not out of pity that most of the larger predatory animals kill their prey quickly. The lion has to finish off a big antelope or a buffalo very quickly indeed in order not to get hurt itself, for a beast of prey which has to hunt daily cannot afford to receive even a harmless scratch in effecting a kill; such scratches would soon add up to such an extent as to put the killer out of action. The same reason has forced the python and other large snakes to evolve a quick and really humane method of killing the well-armed mammals that are their natural prey. But where there is no danger of the victim doing damage to the killer, the latter shows no pity whatsoever. The hedgehog which, by virtue of its armour, is quite immune to the bite of a snake, regularly proceeds to eat it, beginning at the tail or in the middle of its body, and in the same way the water-shrew treats its innocuous prey. But man should abstain from judging his innocently cruel fellow creatures, for even if nature sometimes “shrieks against his creed”, what pain does he himself not inflict upon the living creatures that he hunts for pleasure and not for food?
The mental qualities of the water-shrew cannot be rated very high. They were quite tame and fearless of me and never tried to bite when I took them in my hand, nor did they ever try to evade it, but, like little tame rodents, they tried to dig their way out if I held them for too long in the hollow of my closed fist. Even when I took them out of their container and put them on a table or on the floor, they were by no means thrown into a panic but were quite ready to take food out of my hand and even tried actively to creep into it if they felt a longing for cover. When, in such an unwonted environment, they were shown their nestbox, they plainly showed that they knew it by sight and instantly made for it, and even pursued it with upraised heads if I moved the box along above them, just out of their reach. All in all, I really may pride myself that I have tamed the shrew, or at least one member of that family.
In their accustomed surroundings, my shrews proved to be very strict creatures of habit. I have already mentioned the remarkable conservatism with which they persevered in their unpractical way of entering their nest-box by climbing on to its roof and then vaulting, with a half turn, in through the door. Something more must be said about the unchanging tenacity with which these animals cling to their habits once they have formed them. In the water-shrew, the path-habits, in particular, are of a really amazing immutability; I hardly know another instance to which the saying, “As the twig is bent, so the tree is inclined”, applies so literally.
In a territory unknown to it, the water-shrew will never run fast except under pressure of extreme fear, and then it will run blindly along, bumping into objects and usually getting caught in a blind alley. But, unless the little animal is severely frightened, it moves, in strange surroundings, only step by step, whiskering right and left all the time and following a path that is anything but straight. Its course is determined by a hundred fortuitous factors when it walks that way for the first time. But, after a few repetitions, it is evident that the shrew recognizes the locality in which it finds itself and that it repeats, with the utmost exactitude, the movements which it performed the previous time. At the same time, it is noticeable that the animal moves along much faster whenever it is repeating what it has already learned. When placed on a path which it has already traversed a few times, the shrew starts on its way slowly, carefully whiskering. Suddenly it finds known bearings, and now rushes forward a short distance, repeating exactly every step and turn which it executed on the last occasion. Then, when it comes to a spot where it ceases to know the way by heart, it is reduced to whiskering again and to feeling its way step by step. Soon, another burst of speed follows and the same thing is repeated, bursts of speed alternating with very slow progress. In the beginning of this process of learning their way, the shrews move along at an extremely slow average rate and the little bursts of speed are few and far between. But gradually the little laps of the course which have been “learned by heart” and which can be covered quickly begin to increase in length as well as in number until they fuse and the whole course can be completed in a fast, unbroken rush.
Often, when such a path-habit is almost completely formed, there still remains one particularly difficult place where the shrew always loses its bearings and has to resort to its senses of smell and touch, sniffing and whiskering vigorously to find out where the next reach of its path “joins on”. Once the shrew is well settled in its path-habits it is as strictly bound to them as a railway engine to its tracks and as unable to deviate from them by even a few centimetres. If it diverges from its path by so much as an inch, it is forced to stop abruptly, and laboriously regain its bearings. The same behaviour can be caused experimentally by changing some small detail in the customary path of the animal. Any major alteration in the habitual path threw the shrews into complete confusion. One of their paths ran along the wall adjoining the wooden table opposite to that on which the nest box was situated. This table was weighted with two stones lyin
g close to the panes of the tank, and the shrews, running along the wall, were accustomed to jump on and off the stones which lay right in their path. If I moved the stones out of the runway, placing both together in the middle of the table, the shrews would jump right up into the air in the place where the stone should have been; they came down with a jarring bump, were obviously disconcerted and started whiskering cautiously right and left, just as they behaved in an unknown environment. And then they did a most interesting thing: they went back the way they had come, carefully feeling their way until they had again got their bearings. Then, facing round again, they tried a second time with a rush and jumped and crashed down exactly as they had done a few seconds before. Only then did they seem to realize that the first fall had not been their own fault but was due to a change in the wonted pathway, and now they proceeded to explore the alteration, cautiously sniffing and be-whiskering the place where the stone ought to have been. This method of going back to the start, and trying again always reminded me of a small boy who, in reciting a poem, gets stuck and begins again at an earlier verse.
In rats, as in many small mammals, the process of forming a path-habit, for instance in learning a maze, is very similar to that just described; but a rat is far more adaptable in its behaviour and would not dream of trying to jump over a stone which was not there. The preponderance of motor habit over present perception is a most remarkable peculiarity of the water-shrew. One might say that the animal actually disbelieves its senses if they report a change of environment which necessitates a sudden alteration in its motor habits. In a new environment a water-shrew would be perfectly able to see a stone of that size and consequently to avoid it or to run over it in a manner well adapted to the spatial conditions; but once a habit is formed and has become ingrained, it supersedes all better knowledge. I know of no animal that is a slave to its habits in so literal a sense as the water-shrew. For this animal the geometric axiom that a straight line is the shortest distance between two points simply does not hold good. To them, the shortest line is always the accustomed path and, to a certain extent, they are justified in adhering to this principle: they run with amazing speed along their pathways and arrive at their destination much sooner than they would if, by whiskering and nosing, they tried to go straight. They will keep to the wonted path, even though it winds in such a way that it crosses and recrosses itself. A rat or mouse would be quick to discover that it was making an unnecessary detour, but the water-shrew is no more able to do so than is a toy train to turn off at right angles at a level crossing. In order to change its route, the water-shrew must change its whole path-habit, and this cannot be done at a moment’s notice but gradually, over a long period of time. An unnecessary, loop-shaped detour takes weeks and weeks to become a little shorter, and after months it is not even approximately straight. The biological advantage of such a path-habit is obvious: it compensates the shrew for being nearly blind and enables it to run exceedingly fast without wasting a minute on orientation. On the other hand it may, under unusual circumstances, lead the shrew to destruction. It has been reported, quite plausibly, that water-shrews have broken their necks by jumping into a pond which had been recently drained. In spite of the possibility of such mishaps, it would be short-sighted if one were simply to stigmatize the water-shrew as stupid because it solves the spatial problems of its daily life in quite a different way from man. On the contrary, if one thinks a little more deeply, it is very wonderful that the same result, namely a perfect orientation in space, can be brought about in two so widely divergent ways: by true observation, as we achieve it, or, as the water-shrew does, by learning by heart every possible spatial contingency that may arise in a given territory.
Among themselves, my water-shrews were surprisingly good-natured. Although, in their play, they would often chase each other, twittering with a great show of excitement, I never saw a serious fight between them until an unfortunate accident occurred: one morning, I forgot to reopen the little door of the nest-box after cleaning out their tank. When at last I remembered, three hours had elapsed—a very long time for the swift metabolism of such small insectivores. Upon the opening of the door, all the shrews rushed out and made a dash for the food tray. In their haste to get out, not only did they soil themselves all over but they apparently discharged, in their excitement, some sort of glandular secretion, for a strong, musk-like odour accompanied their exit from the box. Since they appeared to have incurred no damage by their three hours’ fasting, I turned away from the box to occupy myself with other things. However, on nearing the container soon afterwards, I heard an unusually loud, sharp twittering and, on my hurried approach, found my eight shrews locked in deadly battle. Two were even then dying and, though I consigned them at once to separate cages, two more died in the course of the day. The real cause of this sudden and terrible battle is hard to ascertain but I cannot help suspecting that the shrews, owing to the sudden change in the usual odour, had failed to recognize each other and had fallen upon each other as they would have done upon strangers. The four survivors quietened down after a certain time and I was able to reunite them in the original container without fear of further mishap.
I kept those four remaining shrews in good health for nearly seven months and would probably have had them much longer if the assistant whom I had engaged to feed them had not forgotten to do so. I had been obliged to go to Vienna and, on my return in the late afternoon, was met by that usually reliable fellow who turned pale when he saw me, thereupon remembering that he had forgotten to feed the shrews. All four of them were alive but very weak; they ate greedily when we fed them but died none the less within a few hours. In other words, they showed exactly the same symptoms as the shrews which I had formerly tried to keep; this confirmed my opinion that the latter were already dying of hunger when they came into my possession.
To any advanced animal keeper who is able to set up a large tank, preferably with running water, and who can obtain a sufficient supply of small fish, tadpoles and the like, I can recommend the water-shrew as one of the most gratifying, charming and interesting objects of care. Of course it is a somewhat exacting charge. It will eat raw chopped heart (the customary substitute for small live prey) only in the absence of something better and it cannot be fed exclusively on this diet for long periods. Moreover, really clean water is indispensable. But if these clear-cut requirements be fulfilled, the water-shrew will not merely remain alive but will really thrive, nor do I exclude the possibility that it might even breed in captivity.
10
THE COVENANT
Four-feet trotting behind.
Rudyard Kipling
At the dawn of the later stone age, there appears, as the first domestic animal, a small semi-domesticated dog, certainly descended from the golden jackal (Canis aureus). At this time, in north-west Europe, where skeletons of these dogs have been found, there were probably no more jackals, but there is every reason to believe that the turf dog already lived as a true house dog and that the lake dwellers had brought it with them to the shores of the Baltic sea.
But how did stone-age man come by his dog? Very probably without intending it. Whole packs of jackals must have followed in the train of the wandering, hunting hordes of early stone-age man and surrounded his settlements just as the pariah dogs of the East do to-day, of whom no one knows exactly whether they are housedogs run wild, or wild dogs that have taken the first steps towards domestication. And our forefathers took just as few measures against these scavengers, as the Oriental, in his happy-go-lucky way, does to-day. Indeed, the stone-age hunters, for whom the large beasts of prey were still a serious menace, must have found it quite agreeable to know that their camp was watched by a broad circle of jackals which, at the approach of a sabre-toothed tiger or a marauding cave-bear, gave tongue in the wildest tones.
Then, some time or other, to the function of the sentry was added that of a helper in the hunting field. Some time or other, the pack of jackals which used to follow the hunter
in the hope of receiving the entrails of his prey, took to running before instead of behind the hunter; it began to track game and even to bring it to bay. It is very easy to imagine how these pre-historic dogs developed a new type of interest in the larger game animals. Originally, a jackal would show no interest in the trail of a stag or wild horse, since by himself he could not hope to kill and eat it, but it is not too much to assume that, after having repeatedly received entrails or other refuse from that kind of beast, he might have found inducement to follow a trail which, by its scent, reminded him of a good meal. He might even, by a stroke of canine genius, have “conceived the idea” of calling the hunter’s attention to the track. It is remarkable how quickly dogs realize when they can rely on the help of a strong friend. Even my rather cowardly miniature French bulldog would, if accompanied by his friend, a huge Newfoundland, recklessly attack any dog he met. I am not, therefore, crediting the primitive jackal-dogs with too much intelligence when I surmise that, without being consciously trained by man, they learned to track and bring to bay large game animals.
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