Read Ebook: The Girl's Own Paper Vol. VIII No. 355 October 16 1886 by Various Klickmann Flora Editor Peters Charles Active Editor

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Now, however, the Voles, as these creatures ought rightly to be called, are thought to be of sufficient importance to be placed by themselves, and separated from the true beavers.

The voles constitute quite a large group of rodents, including several animals which are popularly ranked among the mice.

One very remarkable characteristic of the voles is the structure of their molar teeth.

Being rodents, they can have but two incisor teeth in each jaw, these teeth being rootless, and so set in their sockets that they are incessantly worn away in front, and as incessantly grow from the base, take the curved form of their sockets, and act much like shears which have the inestimable property of self-sharpening when blunted, and self-renewal when chipped or actually broken off by coming against any hard substance. Were the teeth to be without this power, the animal would run a great risk of dying from hunger, the injured tooth not being able either to do its own work, or to aid its companion of the opposite jaw. Either tooth alone would be as useless as a single blade of a pair of scissors.

There is another notable characteristic of these incisor teeth. If you will examine the incisors of any rodent, whether it be a rat, a mouse, a rabbit, or a beaver, you will see that the tips are "bevelled" off just like the edge of a chisel. This shape is absolutely necessary to keep the tooth in working order. How is this object to be attained?

In the solution of this problem we may see one of the many links which connect art and nature.

Should our readers know anything of carpentering, let them examine the structure of their chisels. They are not made wholly of hard steel, as in that case they would be liable to snap, just as does the blade of a foil when undue pressure is brought to bear upon it. Moreover, the operation of sharpening would be extremely difficult.

So the blade of the chisel is merely faced with a thin plate of hardened steel, the remainder being of softer material.

Now, it is not at all likely that the unknown inventor of the modern chisel was aware of the analogy between art and nature, and would probably have been very much surprised if anyone had stated that he had borrowed his idea from the incisor teeth of the water-rat.

Yet he might have done so, for these teeth are almost wholly formed of ordinary tooth matter, and are faced with a thin plate of hard enamel, which exactly corresponds with the hardened steel facing of a chisel.

Any of my readers who possess skates will find, on examination, that the greater part of the blade is, in reality, soft iron, the steel, which comes upon the ice, being scarcely a fifth of an inch in length. The hardened steel allows the blade to take the necessary edge, while the soft iron preserves the steel from snapping.

Should the skate have been neglected and allowed to become a little rusty, the line of demarcation between the steel and the iron can be distinctly seen. Similarly, in the beaver and the water-rat, the orange-yellow colour of the enamel facing causes it to be easily distinguished from the rest of the tooth. In most of the rodents the enamel is white, and the line of demarcation is scarcely visible.

Now we have to treat of a question of mechanics.

If two substances of different degrees of hardness be subjected to the same amount of friction, it follows that the softer will be worn away long before the harder. It is owing to this principle that the edges of the rodent teeth preserve their chisel-like form. Being continually employed in nibbling, the softer backing of the teeth is rapidly worn away, while the hard plate of enamel upon the front of the tooth is but slightly worn, the result being the bevelled shape which is so characteristic of these teeth.

As all know, who have kept rabbits or white mice, the animals are always engaged in gnawing anything which will yield to their teeth, and unless the edges of their feeding troughs be protected by metal, will nibble them to pieces in a few days. Indeed, so strong is this instinct, that the health of the animals is greatly improved by putting pieces of wood into their cages, merely for the purpose of allowing them to exercise their chisel-edged teeth. Even when they have nothing to gnaw, the animals will move their jaws incessantly, just as if they were eating, a movement which gave rise to the idea that they chewed the cud.

It is worthy of remark that other animals, which, though not rodents, need to possess chisel-edged incisor teeth, have a similar habit. Such is the hippopotamus, and such is the hyrax, the remarkable rock-haunting animal, which in the authorised translation of the Scriptures is called the "coney," and which in the Revised Version is allowed in the margin to retain its Hebrew name, "shaphan."

The enamel also has an important part to play in the structure of the molar teeth. Each tooth is surrounded with the enamel plate, which is so intricately folded that the tooth looks as if it were made of a series of enamel triangles, each enclosing the tooth matter.

This structure is common to all the members of the group to which the water-rat belongs. It is the more remarkable because we find a somewhat similar structure in the molar teeth of the elephants, which, like the rodents, have the incisor teeth largely developed and widely separated from the molars.

There is nothing in the appearance of the water-rat which gives any indication of its aquatic habits.

For example, we naturally expect to find that the feet of swimming animals are webbed. The water-loving capybara of South America, the largest existing rodent, has its hoof-like toes partially united by webs, so that its aquatic habits might easily be inferred even by those who were unacquainted with the animal. Even the otter, which propels itself through the water mostly by means of its long and powerful tail, has the feet furnished with webs. So has the aquatic Yapock opossum of Australia, while the feet of the duck-bill are even more boldly webbed than those of the bird from which it takes its popular name. The water-shrews are furnished with a fringe of stiff hair round the toes which answers the same purpose as the web.

But the structure of the water-rat gives no indication of its habits, so that no one who was unacquainted with the animal would even suspect its swimming and diving powers. Watch it as long as you like, and I do not believe that you will see it eating anything of an animal nature.

I mention this fact because it is often held up to blame as a mischievous animal, especially deserving the wrath of anglers by devouring the eggs and young of fish.

As is often the case in the life-history of animals as well as of men, the blame is laid on the wrong shoulders. If the destruction of fish be a crime, there are many criminals, the worst and most persistent of which are the fish themselves, which not only eat the eggs and young of other fish, but, Saturn-like, have not the least scruple in devouring their own offspring.

Scarcely less destructive in its own insidious way is the common house-rat, which eats everything which according to our ideas is edible, and a good many which we might think incapable of affording sustenance even to a rat. In the summer time it often abandons for a time the house, the farm, the barn, and seeks for a change of diet by the brook. These water-haunting creatures are naturally mistaken for the vegetable-feeding water-vole, and so the latter has to bear the blame of their misdoings.

There are lesser inhabitants of the brook which are injurious both to the eggs and young of fish. Among them are several of the larger water-beetles, some of which are so large and powerful that, when placed in an aquarium with golden carp, they have made havoc among the fish, always attacking them from below. Although they cannot kill and devour the fish at once, they inflict such serious injuries that the creature is sure to die shortly.

I do not mean to assert that the water-vole is never injurious to man. Civilisation disturbs for a time the balance of Nature, and when man ploughs or digs the ground which had previously been untouched by plough or spade, and sows the seeds of herbs and cereals in land which has previously produced nothing but wild plants, he must expect that the animals to whom the soil had been hitherto left will fail to understand that they can no more consider themselves as the owners, and will in consequence do some damage to the crops.

Moreover, even putting their food aside, their habits often render them obnoxious to civilised man. The mole, for example, useful as it really is in a field, does very great harm in a garden or lawn, although it eats none of the produce.

The water-vole, however, is doubly injurious when the field or garden happens to be near the water-side. It is a mighty burrower, driving its tunnels to great distances. Sometimes it manages to burrow into a kitchen-garden, and feeds quite impartially on the different crops. It has even been seen to venture to a considerable distance from water, crossing a large field, making its way into a garden, and carrying off several pods of the French bean.

In the winter time, when other food fails, the water-vole, like the hare and rabbit, will eat turnips, mangold-wurzel, the bark of young trees, and similar food. Its natural food, however, is to be found among the various aquatic plants, as I have often seen, and the harm which it does to the crops is so infinitesimally small when compared with the area of cultivated ground, that it is not worthy of notice.

Still, although the harm which it does to civilised man in the aggregate is but small, even its most friendly advocate cannot deny that there are cases where it has been extremely troublesome to the individual cultivator, especially if he be an amateur.

There are many hard men of business, who are obliged to spend the greater part of the day in their London offices, and who find their best relaxation in amateur gardening; those who grow vegetables, regarding their peas, beans, potatoes, and celery with as much affection as is felt by floriculturists for their roses or tulips.

Nothing is more annoying to such men than to find, when the toils of business are over, and they have settled themselves comfortably into their gardening suits, that some marauder has carried off the very vegetables on which they had prided themselves.

The water-vole has been detected in the act of climbing up a ladder which had been left standing against a plum tree, and attacking the fruit. Bunches of grapes on outdoor vines are sometimes nipped off the branches by the teeth of the water-vole, and the animal has been seen to climb beans and peas, split the pods, and devour the contents.

Although not a hibernating animal, it lays up a store of food in the autumn. Mr. Groom Napier has the following description of the contents of a water-rat's storehouse:--

"Early in the spring of 1855, I dug out the burrow of a water-vole, and was surprised to find at the further extremity a cavity of about a foot in diameter, containing a quantity of fragments of carrots and potatoes, sufficient to fill a peck measure. This was undoubtedly a part of its winter store of provisions. This food had been gathered from a large potato and carrot bed in the vicinity.

"On pointing out my discovery to the owner of the garden, he said that his losses had been very serious that winter owing to the ravages of these animals, and said that he had brought both dogs and cats down to the stream to hunt for them; but they were too wary to be often caught."

I do not think that the owner of the garden knew very much about the characters either of the cat or water-vole.

Every one who is practically acquainted with cats knows that it is next to impossible to point out an object to a cat as we can to a dog. She looks at your finger, but can never direct her gaze to the object at which you are pointing. In fact, I believe that pussy's eyes are not made for detecting objects at a distance.

If we throw a piece of biscuit to a dog, and he does not see where it has fallen, we can direct him by means of voice and finger. But, if a piece of meat should fall only a foot or two from a cat, all the pointing in the world will not enable her to discover it, and it is necessary to pick her up and put her nose close to the meat before she can find it.

So, even, if a water-vole should be seen by the master, the attention of the cat could not be directed to it, her instinct teaching her to take prey in quite a different manner.

The dogs, supposing that they happened to be of the right breed, would have a better chance of securing the robber, providing that they intercepted its retreat to the water. But if the water-vole should succeed in gaining its burrow, or in plunging into the stream, I doubt whether any dog would be able to catch it.

Moreover, the water-vole is so clever in tunnelling, that when it drives its burrows into cultivated ground, it almost invariably conceals the entrance under a heap of stones, a wood pile, or some similar object.

How it is enabled to direct the course of its burrow we cannot even conjecture, except by attributing the faculty to that "most excellent gift" which we call by the convenient name of "instinct."

Man has no such power, but when he wishes to drive a tunnel in any given direction he is obliged to avail himself of levels, compasses, plumb-lines, and all the paraphernalia of the engineer. Yet, with nothing to direct it except instinct, the water-vole can, though working in darkness, drive its burrow in any direction and emerge from the ground exactly at the spot which it has selected.

The mole can do the same, and by means equally mysterious.

I may casually mention that the water-vole is one of the aquatic animals which, when zoological knowledge was not so universal as it is at the present day, were reckoned as fish, and might be eaten on fast days. I believe that in some parts of France this idea still prevails.

With all its wariness, the water-vole is a strangely nervous creature, being for a time almost paralysed by a sudden shock. This trait of character I discovered quite unexpectedly.

Many, many years ago, when I was a young lad, and consequently of a destructive nature, I possessed a pistol, of which I was rather proud. It certainly was an excellent weapon, and I thought myself tolerably certain of hitting a small apple at twelve yards distance.

One day, while walking along the bank of the Cherwell River, I saw a water-vole on the opposite bank. The animal was sitting on a small stump close to the water's edge. Having, of course, the pistol with me, and wanting to dissect a water-vole, I proceeded to aim at the animal. This was not so easy as it looked. A water-vole crouching upon a stump presents no point at which to aim, the brown fur of the animal and the brown surface of the old weather-beaten stump seeming to form a single object without any distinct outline; moreover, it is very difficult to calculate distances over water. However, I fired, and missed.

I naturally expected the animal to plunge into the river and escape. To my astonishment, it remained in the same position. Finding that it did not stir, I reloaded, and again fired and missed. Four times did I fire at that water-vole, and after the last shot the animal slowly crawled off the stump, slid into the river, and made off.

Now in those days revolvers and breech-loaders did not exist, so that the process of loading a pistol with ball was rather a long and complicated one.

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