Popular Science Monthly/Volume 38/November 1890/Habits of the Box Tortoise
|HABITS OF THE BOX TORTOISE.|
By ALFRED GOLDSBOROUGH MAYER, M. E.
WITH DRAWINGS BY THE AUTHOR.
WHO has not been charmed by the many quaint and interesting narratives of the habits of animals, left to us by that father of English natural history Gilbert White? The philosopher vicar, far from the troubled world, among the peaceful beauties of Selborne, devoted a long life to the study of nature. Among his favorite pets was "the old tortoise" named Timothy; and many a letter to the Honorable Daines Barrington gives minute and careful descriptions of its peculiar actions and intelligence. There is a joyful ring in the old gentleman's tone when he finds the tortoise "distinguishes the hand that feeds it, and is touched with the feelings of gratitude"; again, we find him lost in wonder at its extreme old age; or marveling that an animal so completely protected should have such fear of rain as to crowd against the stone wall and close itself up. Then the vicar's head bows sadly, with the air of a melancholy Jacques, as he watches his pet's amorous wanderings in early summer.
Fig. 1.—The Box Tortoise. (Side view.)
In America we also have a land tortoise, whose ways and modes of life are quite as interesting as those of White's Timothy. It is a little creature not more than five and a half inches long when full grown. No two individuals are marked alike. Before the attainment of full growth the shell is corrugated by numerous concentric ridges. As a new one is formed every year, the age of the tortoise may be obtained by counting these ridges, provided it be not full grown; for in old age the shell becomes smooth and polished. Some are of a brownish horn color streaked with rich yellow, others are black covered with oval yellow spots. The color of the legs and head varies from dark brown to bright yellow. Frequently the old males have blood-red eyes, which give them a ferocious appearance.
The box tortoise is most commonly to be met with in shady places, near the borders of woods; or near damp or marshy ground, where worms and insects abound. The tortoise has quite an aversion for wet places, and, although it is a fairly good swimmer, and can remain for over twelve hours beneath the surface without once coming out to breathe, it is rarely to be found in the water. In May and early summer it deserts the shade of the woods where it has spent the winter, and moves into the open meadows, where the fresh young grass is becoming thick and high, myriads of insects are waking into life, and the wild strawberries are beginning to redden. After the pastures are mowed in July the tortoises scatter, some remaining in the meadows, others taking again to the woods. For this reason the animal is much more, rarely met with in August than in June.
Owing to the extreme slowness and deliberation of all its movements, it seems wonderful that it can obtain enough to eat. Often it will hesitate for a full minute, on finding an insect, before summoning up enough resolution to seize it. The neck is slowly stretched forward, the jaws open and close upon the victim, and the head is immediately snapped back as though frightened at what it had done. Deglutition is accomplished by a series of gulping movements, which often cause a squealing sound. Its food consists of crickets, grasshoppers, caterpillars, worms, and, in fact, almost any luckless insect which it may find. It is very partial to wild strawberries, tomatoes, and many fungi. There can be no doubt that it greatly aids the farmer by destroying the larvæ of injurious insects. In seeking its food the tortoise wanders about in the most zigzag courses imaginable. A whole day's wanderings, of over half a mile, may not cover more than a quarter of an acre. Our little friend rarely wanders far from the place of his birth. In the month of May, 1880, a dozen tortoises found in a three-acre pasture were marked by the writer. Every year they return to the same meadow, so that in 1889 eight of them were identified. The most erratic individual was found half a mile from the meadow, six years after being marked. The tortoise is very generally distributed over the United States east of the Mississippi, but its local distribution is variable. In some sections it is very common, in others extremely rare. On the approach of the frost, about the middle of October, the tortoise burrows about a foot beneath the fallen leaves of the woods, or into soft, marshy ground, and there passes the winter in a torpid state. About the middle of April it digs its way upward again, and may be seen crawling slowly about, covered with caked and frozen mud.
But the most remarkable ability of the little reptile is his power to entirely withdraw himself within his shell, and then to close up the openings. Observing the approach of an enemy, he rapidly draws in his head, legs, and tail, giving expression to his displeasure by a sharp hiss; then, folding up the two flaps of the lower shell until they fit accurately into the cup-shaped edge of the upper, he becomes as unopenable as an oyster. In most cases the fit of the carapace and plastron is so perfect that it would be difficult to insert the head of a pin into any crack, and the muscles are so powerful as to render it well-nigh impossible to force an opening. Yet the jaguar of South America has been seen to tear open the shells of similarly protected tortoises. We may feel assured that the protection is a needed one, for it is very rare to find an old box tortoise whose shell does not show marks of rough usage.
There is a well-grounded popular belief that our tortoise lives to a vast age, and numerous cases of turtles bearing dates over a century old have been cited. There was, until 1886, in the neighborhood of the writer's home in New Jersey, an old tortoise which had been marked by Mr. Cyrus Durand, the inventor of the geometric lathe It bore the inscription "C. D. 1838," clearly cut with a graver, on its under shell. As the tortoise had been observed from year to year since the time of its marking by the most trustworthy witnesses, there can be no doubt that the date was genuine. This tortoise has not been seen since 1886, so it has probably died. Another, which has been observed for the past nine years, was marked with the inscription "C. B., 1849"; as the letters and date were so much worn as to be but faintly discernible, they were doubtless reliable. This old animal was found for the last time, dead, in the summer of 1889. Another, bearing the date 1851, is still alive. Assuming that the tortoises were full grown, or about twenty years old when marked, we are safe in stating the period of their lives as from sixty to seventy years. No doubt some individuals may reach a century or over. Unfortunately for science, it is a common sport for the country urchin to engrave tortoises with dates varying from forty to fifty years before the artist's birth. This, however, can almost always be detected, for the inscription becomes very faint after thirty years of rubbing over the ground. In fact, it would seem impossible that an inscription could last for a hundred years, as the growth of the shell and the constant friction would probably obliterate it.
The tenacity of life in all tortoises is remarkable The heart will continue to pulsate for over three quarters of an hour after being cut out of the body, and the animal is said to have lived for several months after the brain had been removed. There seems to be fully as much fat about the muscles of tortoises which have just awakened from the winter's sleep as there was in the preceding autumn. Doubtless they could remain torpid for over a twelvemonth, and then recover.
The mating season of our box tortoise occurs during the first three weeks in May. The males are unusually active during this period, and will fight savagely among themselves. The author was once fortunate enough to witness one of these combats. Two old males were facing one another; using the front flaps of their plastrons for shields, they would charge, snapping viciously, and whenever one obtained a grip he would hang on with bull-dog tenacity. The noise made by their shells knocking together could be heard two hundred feet away. After an hour or more the smaller male began to show signs of exhaustion, his charges became weaker and weaker, until finally he closed his shell tightly and refused to fight. The victor, after snapping at the unresponsive shell for a few moments, crawled deliberately over the back of his shut-up adversary. It was found upon examination that neither of the combatants had received any visible injury, so well did their armor of shells and scales protect them.
All turtles are oviparous, depositing their eggs in the ground and leaving them to be hatched by the heat of the sun. The laying period of our box tortoise extends from the 7th to the 20th of June. A few females lay in the autumn, but this seems to be a perverted instinct, and not a regular habit of the species. They always lay at night, and deposit all their eggs in a single nest. As soon as the sun goes down the female sets about her maternal duties. She wanders over the fields with restless activity until she finds a locality suitable for the formation of the nest. Stubble-fields, or those which, having been recently under cultivation, are covered with a thin growth of grass, are preferred. She then begins to scratch up the earth with her hind feet, using first one
Fig. 3.—Old Males fighting. Showing extreme variation in the coloring of the species. (From a sketch made at the time.)
and then the other. After about three hours of patient labor, a small hole about four inches in depth and two inches in diameter, a little wider at the bottom than at the top, has been excavated. An egg is then dropped into the cavity and carefully pushed against the side by the hind foot of the mother; another is then laid and placed in position as before, until from four to six eggs are ranged side by side in the bottom of the nest. The earth is then carefully scraped back by the hind feet, and finally the grass and leaves are scratched over the opening and pressed down so skillfully that the ground appears as though it had never been broken. By this time it is past midnight It is remarkable that the females do not seem to fear the presence of the observer, but continue their labors, although he may be but a foot or two away. When once started digging the nest they rarely abandon the work. We have observed a tortoise of another species (Nanemys guttata) which dug all night, and finally completed its nest on the noon of the day following.
The eggs are covered with a soft white calcareous shell. They are of an oval shape, 1·28 inch long and ·91 inch in diameter. When carefully blown they will retain their form. The shell is very hydroscopic, and, if the eggs be placed in alcohol or glycerin, they soon shrivel, owing to the abstraction of water from the interior. The young hatch late in October, just in time to move into winter quarters.
The disposition of our box tortoise is timid and gentle. If kept for a pet, it soon becomes very tame, and will eat from the hand of its master, whom it may even grow to recognize. In captivity it displays a great variety of tastes, and will readily take to cooked meat, vegetables, or bread.
Of all the lower vertebrates the tortoises exhibit, perhaps, the most marvelous regularity in their habits.
Thus the duration of the laying period is a very short time, usually in June, and rarely extending over two weeks for each species. It seems to be independent of the severity or mildness of the season, but occurs with wonderful regularity year after year. The same rule seems to apply to the time of hibernation. Seven young tortoises of various species, which were kept in an aquarium in a warm room, simultaneously refused to eat on the 5th of October, and went into hibernation just as they would have done if in the open air. They remained buried in the mud beneath the water, or huddled up asleep upon the land, and touched no food for over two months. Sometimes, when the aquarium was exposed to the full heat of the sun, one or two would awaken and crawl slowly about, but it was extremely difficult to induce them to eat.
A turtle's heart consists of two auricles and only one ventricle; so, the blood is never completely aerated and is therefore, comparatively speaking, "cold." This is the reason that tortoises, especially those species which inhabit our rivers and ponds, delight to bask for hours, exposed to the full glare of the hottest sun.
Millions of years ago, when marshes covered the greater part of the face of the earth, the reptiles were of huge size and strength. The turtles of to-day are but the pygmy descendants of these giant ancestors. Protected by their bony coverings, or relying upon their knife-like jaws and savage dispositions, they have survived in stunted form until to-day. Now, in this age of man, many species bid fair to outlive the wanton destruction which is fast depriving our woods and meadows of the wild creatures which once knew them as a safe retreat. The beaver, the gray squirrel, the wild pigeon, will soon be no more; but the lover of nature may still find our tortoise for his study and amusement.