Popular Science Monthly/Volume 42/February 1893/Habits of the Garter Snake
|HABITS OF THE GARTER SNAKE.|
AMONG those many creatures which know our fields and forests for their homes, is the little garter snake; or, as naturalists would have us dub him, Eutænia sirtalis. If one will but overcome a deep-rooted antipathy to crawling things, and will exchange the city's heat and turmoil for a few weeks of outing in the pure air of our sweet-scented fields, and make our little friend's acquaintance, much that the observer will not willingly forget will be his reward. When the snake is full grown, it is usually a little less than three feet long. The color is very variable, the usual body hues being brownish olive, sometimes with darker patches upon the sides, and generally there is a lighter yellowish streak down the middle of the back.
The belly plates are greenish blue or yellow, and the tongue is bright red, tipped with jet black. When angry, the snake spreads out its easily movable ribs, so as to make itself as broad and ugly as possible, and then one sees patches of white flecks between the scales on the sides. The general effect of the markings is so much like that of the ground upon which the reptile is crawling that even an observant naturalist rarely sees anything of his snakeship until he finds him almost under foot. All snakes crawl by side twists, and not by up and down undulations. They move themselves along by taking advantage of the friction between the sharp edges of the abdominal plates and the ground. The numerous ribs which can be moved forward and backward, as well as up and down, aid them greatly in their progress; and all the movements are performed with such gliding grace that one imagines the serpent to be impelled onward by some hidden, mysterious force. Place the Fig. 1.—Head of Garter Snake. snake upon a smooth glass surface, however, and it writhes and squirms in a helpless fashion. The garter snake is an excellent swimmer, making rapid progress through the water by means of a rhythmical sinusoidal movement of the submerged body, the little head being always just above the surface. It is a lazy creature, possessed of little desire to see the world, for it rarely wanders far from the place of its birth, as long as food remains abundant. It loves the sunny borders of swamps and ponds, where frogs and earthworms abound, and where it may bask exposed to the hot glare of the noonday sun, or seek a safe retreat beneath fallen logs or among the crevices of rocks. Its one idea is to warm up its cold blood by heat borrowed from the sun, and its life is one of apathetic indolence, except when in search of prey. Then the serpent steals stealthily through the grass; every now and again its slender neck elevates, and the cold, stony eyesFig. 2.—Skull of Garter Snake. dart a hasty glance to right and left. The red tongue flashes forth two or three times and it renews the search. And now, down beside the mossy bank of the brook, it espies a luckless frog, unconscious of the gliding foe behind. The snake half coils, then springs, and seizes its victim in a viselike grip. Struggles only serve to drive in the little needlelike teeth deeper and deeper, for they are all pointed backward, as one may see by looking at the picture of the skull (Fig. 2). The serpent recoils, dragging the resisting prey more and more hopelessly away from its watery retreat. The method of swallowing is a very simple one, although, if the frog be large, more than half an hour may be consumed in the process. The two bones of the lower jaw are separate and capable of independent movement; so the reptile loosens its hold upon one side of its jaw, and, pushing that side forward as far as possible, it drives the teeth in again, and then draws the jaw back to its original position. The result is that the prey is drawn down by the movement. The process is then repeated by the other half of the jaw, thus inevitably forcing the victim inward. The snake's skin stretches enormously, and the jaw is, of course, dislocated, but the extensible ligaments hold the bones together. The disproportion between the diameter of the frog and the serpent's slender neck is indeed marvelous, and snakes have been observed to split themselves open by attempting too ambitious a mouthful. After perhaps half an hour of laborious contortions, all that is seen of the poor frog is a great swelling that the contracting muscles are rapidly forcing down the reptile's neck. If one liberates the captured frog before it is too late, the wretched animal often seems so overcome by fear, or perhaps stupefied by the serpent's saliva, that it will not leap, but crawls in a painful manner. We must not allow ourselves to be duped into a mistaken sympathy, however, for such is the poetic justice of the case. Large frogs esteem small snakes a particular delicacy. After such a dinner as the above, the snake seeks some safe retreat and there lapses into a more or less quiescent state for about a week, at the end of which time it is ready to add another victim to its list. Frogs are not, however, the only food of the garter snakes; they will also feed upon newts or toads, they are very partial to earthworms, and in rare instances will resort to cannibalism. They never feed upon insects, and as far as my observation goes will not attack birds or mice. There is a great difference between the arrangement of the teeth in harmless and venomous snakes. The harmless garter snake, for example, possesses four rows of little needlelike teeth upon its upper jaw. All these teeth are of about the same size, and are pointed backward. A bite from such a snake would leave an impression similar to that shown in A, Fig. 3, where the dots represent the perforations made by the teeth. Venomous snakes, on the other hand, possess much fewer teeth, and in the outer rows we find several large fangs. An impression from a snake of this sort is shown in Fig. 3, B. Several times during the summer the garter snake molts. Almost a week before this takes place, the horny layer of the old epidermis begins to separate from the underlying skin. This separation is caused by numerous little hairlike structures, called lifting hairs, which develop uniformly all over the underlying epidermis and push the old skin away from it, so that it hangs loosely all over the body. The snake becomes torpid and irritable. The eyes lose their luster and become milky in appearance, for the cuticula overFig. 3.—Forms of Snake-bites. the eyes is shed also. Finally, the skin breaks around the lips and the serpent proceeds to cast it off, which it usually accomplishes in about an hour by writhing slowly through the grass, so that the whole skin is turned inside out, and pulled off backward like the finger of a glove.
The mating season of the garter snake comes about the middle of April, very soon after it awakens from the winter's hibernation. The males possess the mysterious power of tracking the females through the grass, and will follow after all the sinuosities of their paths with the greatest certainty. At this season both sexes emit a very rank and disgusting odor, especially when irritated.
During the months of June and July the females may be observed basking themselves in the hottest sun. They are very easily angered at this time, and generally make a bold front, snapping viciously at the intruder. They refuse to eat in captivity for about a month before the birth of the young, which usually occurs during the latter half of August. The young snakes are born alive, or rather break through their egg membranes immediately upon being born. The number of young produced by a single full-grown snake is usually about fifty, although, according to the observations of Mr. C. Tew Seiss, it may vary from thirteen to eighty. To give an idea of the enormous dangers which threaten the lives of the little snakes, it isFig. 4.-Young Garter Snake, One Day Old.
Natural size. easily calculated that if the garter snake arrive at maturity at the end of three years, and then produces an average of forty young at a birth, a single pair of mature snakes will have become the progenitors of over one hundred and seventy thousand at the end of the eighth year.
The young serpents are usually about five and a half inches long; they are lively, active little fellows, colored very much like their parents, and have large, bright eyes, which give them a staring, surprised look, for snakes have no eyelids and can, therefore, never vary their expression. At the end of two or three days they grow hungry enough to eat, and will pounce upon and devour earthworms with much avidity. Very amusing indeed is it when two little snakes seize upon opposite ends of the same worm, for the fight only ends when one of the serpents attempts to swallow his brother, worm and all. Earthworms, however, can not be their only food, for the garter snake is exceedingly abundant where earthworms are very rare, as in the Canada woods. I have never observed the mother snake guard her progeny, and believe that the little ones scatter immediately to seek their fortunes.
Early in October the garter snakes huddle together in convenient crevices where they hibernate for the winter. As the food of the garter snake consists very largely of frogs and toads, it is probably an enemy to the agriculturist. If we examine carefully the leaves of our trees in late August it will be found that a perfect leaf is indeed rare; very few have escaped the ravages of numerous insect enemies. In this fact we find but another example of the great law of interdependence of organisms. The greatest enemies of the leaves are the insects; frogs and toads depend upon insects for their food, and snakes, in their turn, feed upon frogs and toads. So that we see that the more snakes the more insects, and the fewer perfect leaves will we find in late summer.