The Animal World, A Book of Natural History Part 43

RATTLESNAKES

Several different species of rattlesnakes are scattered over the United States, and in some places, as on the hot dry plains of the Southwest, and in the arid mountains of Utah and California, are numerous enough to be troublesome. The cutting away of forests, draining of swamps, and cultivation of prairies, soon destroy these pests in thickly settled regions; but where rocky hills occur they linger for a long time, because the breaks and little caves among the ledges offer them secure retreats, winter homes where they sleep in safety, and proper nurseries for the young, which are not produced from eggs, as in the coluber family, but are born alive.

The rattles from which these serpents take their name, are a number of hollow, h.o.r.n.y, b.u.t.ton-like structures at the tip of the tail, which rattle together, with a peculiar humming sound, when the creature shakes its tail, as it is sure to do when disturbed or angry. It thus gives a warning to the man who might not have noticed the sluggish creature in his path in time to jump aside. Not all of the tribe have a rattle, however; and one of the reasons why our water-moccasin and copperhead are so much dreaded is that they possess no rattle, and therefore sound no "keep-off" warning.

All our American venomous snakes are too heavy and slow to climb trees.

They get their prey--mice, gophers, snakes, etc.--by going to a place where it is likely to be running about, and then patiently waiting until something comes within striking distance.

CHAPTER XXIX

AMPHIBIANS

You will remember that the amphibians are distinguished from the true reptiles by having to pa.s.s through a tadpole stage before they obtain their perfect form. A good example is the frog, which in one kind or another exists in all parts of the earth except the very coldest. No doubt, you have often seen great ma.s.ses of its jelly-like sp.a.w.n floating on the surface of ponds early in the spring; and you must have wondered how such small creatures as frogs could possibly lay such enormous batches of eggs.

But the fact is that when these eggs are first laid they are very tiny.

Each egg is only about as big as a small pin's head. Instead of having sh.e.l.ls, however, they are covered with a very elastic skin, while at the same time they soak up water. So, as soon as they pa.s.s into the pond they begin to swell, and very soon each egg is as big as a good-sized pea.

TADPOLE AND FROG

In the middle of each egg is a round black spot, which increases in size every day. This is the future tadpole, and after a time the egg-skin splits, and out it tumbles into the water.

It is an odd-looking creature--just a big round head with a tiny pair of gills and a little wavy tail, and nothing else at all. But it manages to swim by wagging its tail, and it feeds on the tiny sc.r.a.ps of decaying matter which are always floating about in the water of the pond. Before long a little pair of legs begin to show themselves just at the base of the tail. A few days later another pair begin to grow in front of them.

Then, by slow degrees, the tail pa.s.ses back into the substance of the body, and so do the gills, while lungs are developed and nostrils are opened. And by the time that all these changes have taken place the tadpole has ceased to be a tadpole and has turned into a frog.

It leaves the water now and lives upon land, feeding upon small insects, which it catches in a most curious way. Its tongue is turned, as it were, the wrong way round; for the root is just inside the lips, while the tip is down the throat. Besides this, the tongue is very elastic and very sticky. So the animal catches its victims just as the chameleon does, flicking out its tongue at them and just touching them with the tip, to which they adhere. And as the tongue is drawn back into the mouth it pokes them down the throat; so that frogs do not even have to take the trouble of swallowing their dinner.

If you look at a frog's hind feet, you will notice that the toes are joined together by webbing. This allows them to be used in the water as well as upon dry land. It is generally said that frogs swim. But if you watch them in the water you will see at once that they do not really swim at all, but leap along, just as they leap along the ground. And each leap carries them through the water for some little distance.

TOADS

In some ways toads are like frogs; but you can tell them at once by their rough, dry skins, which are covered with warts like glands. And they crawl over the ground, instead of leaping as frogs do. They are very common almost everywhere, and you may often find them hiding under logs or large stones during the daytime.

Toads do not lay their eggs in great ma.s.ses, as frogs do, but arrange them in strings about four feet long and an eighth of an inch wide. Each of these strings consists of two rows of eggs fastened side by side together. The tadpoles are very much like those of the frog, the chief difference being that they are rather smaller and blacker.

NEWTS

All through their lives newts keep their tails, instead of losing them when they cease to be tadpoles.

You can find newts in plenty all through spring and summer by fis.h.i.+ng with a small net in any weedy pond; but you will find that they are not all alike. Some have wavy crests running all along their backs; others have none; and some are brightly colored while others are plain olive green all over. Often in the woods in certain parts of the United States you will meet with little newts traveling about on the damp old leaves; and they are very conspicuous because of their brilliant vermilion color. These are young green newts which come out of the water, live ash.o.r.e for a year or so in the red suit, and then go back to the water and a green coat.

Newts lay their eggs in a very curious manner. They do not fasten them together in great batches, like the frog, or in long, narrow strings, like the toad. They lay them one by one. And the mother newt takes each egg as she lays it, places it in the middle of the narrow leaf of some water-plant, and then twists the leaf neatly round it with her little fore feet, so as to wrap it up in a kind of parcel! The tadpole which hatches out of this egg is very much like that of a toad or a frog; but the front legs are the first to appear, instead of the hind legs, while the tail, of course, does not pa.s.s back into the substance of the body.

Newts swim with their tails, and very pretty and graceful they look as they move through the water. When they cease to be tadpoles, of course, they breathe air, just as toads and frogs do, and have to come up to the surface every two or three minutes to obtain it. And as long as they live in the pond they feed upon grubs and worms and tiny water-insects.

SALAMANDERS

The curious creatures known as salamanders are related to the newts, and begin their lives in just the same way. But after they have ceased to be tadpoles they only visit the water for two or three weeks in the spring.

The most celebrated member of this group is the spotted salamander, which is found in Central and Southern Europe, and also in Algeria and Syria. When fully grown it is about eight inches long, and may be known at once by the two rows of large yellow blotches which run down from the back of its head, right along its body, to the very tip of its tail.

In days of old it was thought that the salamander had the power of walking through fire without being burnt! And it was also supposed, if it were attacked, to spring upon its enemy, bite out a piece of his flesh, and then spit fire into the wound! As a matter of fact it is almost harmless, and may be picked up and handled without the slightest danger. But the glands on its skin, like those on the toad's head and back, contain a rather poisonous fluid, which is squirted out if they are squeezed. So that if a dog were to pick up a salamander he would be quite sure to drop it again very quickly, and would most likely foam at the mouth for some little time.

Salamanders are very slow and timid creatures, and generally spend the whole of the day concealed in some crevice, or in the hollow trunk of a tree, or perhaps under a large stone. They feed upon slugs and small insects.

There are several kinds in North America, some of which, as the h.e.l.lbender, are a foot or more in length.

The giant salamander, which is sometimes nearly a yard long, is found in the rivers of China and j.a.pan, and spends the whole of its life in the water. It feeds chiefly upon fishes.

THE AXOLOTL

This is one of the most singular of all the amphibians. It is found in North America. Sometimes it develops into its perfect form, and sometimes it remains a tadpole all its life, and yet lays eggs just as though it were adult!

In the lakes of the southern Rocky Mountains the life of this creature is just like that of any other batrachian. That is, it is hatched out of the egg as a tadpole, grows first one pair of legs and then another, loses its gills by degrees, and at last appears in a lizard-like form, leaving the water and living upon dry land. But in the lake which surrounds the city of Mexico it never becomes anything more than a big tadpole, keeps its gills throughout its life, and does not leave the water at all.

THE OLM

The olm, or proteus, is found only in the underground lakes of Carniola and one or two other parts of Central Europe. It is about a foot long when fully grown, and has a slender, snake-like body, with a pair of tiny legs just behind the head, and another pair at the base of the tail. It is perfectly blind, the eyes being hidden under the skin, and yet cannot bear light. For if it is kept in captivity it will always hide in the darkest corner that it can find. And it has been known to live in confinement for five years without once taking any food.

What the habits of this extraordinary animal are in nature no one knows, as it has never been found except in these underground lakes.

In color the olm is pinkish gray, with bright-red gills, and there are from twenty-four to twenty-seven grooves upon either side of its body.

FISHES

CHAPTER x.x.x

FRESH-WATER FISHES

The lowest cla.s.s of the vertebrate animals consists of the fishes. These are easily distinguished. Some of the reptiles, it is true, are very fish-like. But then they have three chambers in their hearts, while the true fishes only have two. Then fishes never have limbs, the place of which is taken by fins; and further, they breathe water by means of gills. There are other differences as well; but these are quite sufficient to show us that reptiles and fishes cannot possibly be mistaken for one another.

Between the two, however, come several very curious creatures, which seem to be partly reptiles and partly fishes; for they have four slender members which hardly seem to be legs, though they cannot possibly be described as fins, while they possess not only gills but lungs as well.