LIZARDS AND CHAMELEONS—TURNCOATS OF THE WOODS
Lizards (Lacertilia) are creatures of hot climates, and especially of deserts, and they exhibit an almost endless variety of shape, size, structure, and adaptations to their surroundings and a mode of life that is primarily dictated by their food. The majority are terrestrial, but some species are semiaquatic. There are climbing, swiftly running, and even flying forms, while others lead a subterranean life like earthworms. Most of them subsist on animal food, varying from tiny insects and worms to birds and mammals, while others live upon a vegetable diet.
Lizards, like snakes, have a scaly skin covered with a thin, horny pellicle which is shed from time to time, flaking off in pieces except in the wormlike species, where it is sloughed whole as by snakes. In most lizards the scales are well developed, and "shingle" the back and sides of the body, but in some they are like little tubercles, giving a granular appearance—a good example of which is the "Gila monster" of Arizona. Lizards are, as a rule, adaptively colored according to their habitat, so that browns and grays prevail in the sand-running species or those, like the monitors and iguanas, that are mostly aquatic; but brilliant hues in varied, even fantastic, patterns adorn many of the small, agile, tropical kinds, whose safety lies in their swiftness of movement and cleverness in hiding. This is supplemented in most species by the capability of changing color, a faculty that is most serviceable in the chameleons, by rendering them more or less invisible to the hawks and other animals that try to catch and eat them. Some of the more sluggish, earth-dwelling kinds are further protected by many spines sprouting from the skin, as is familiar in our western "horned toad," and in the fearsome-looking "moloch" of Australia; and the iguanas are provided with an erectile spiny crest along the ridge of their backs, most notable in the basilisks.
A strange characteristic of most lizards with slender tails is the power to part with them at a moment's notice. If an enemy seizes this appendage, which often is held temptingly aloft, it breaks off and its owner escapes before the would-be captor has had time to recover from his surprise. Within a short time a new tail is developed, but it is never so perfect as the original organ.
Most lizards lay eggs, few in number, and with shells hard in some families, parchmentlike in others, that are hidden in a hole in a dead stump or some similar place of concealment, and are left to be hatched by the warmth of the sun. Many lizards retain their eggs until nearly ready to hatch, and so are practically viviparous. The embryos have an "egg tooth," as do turtles and snakes.
The Lacertilia are naturally divisible into three sections, namely, geckos, typical lizards, and chameleons.
The geckos are a large and ancient family represented in all tropical countries, and some species are common along both shores of the Mediterranean, but none reach the United States. They are small, plump, flat-headed, and mostly somber in color, but this is changeable; the skin has a granular surface, but regular scales cover the desert-dwelling species. One peculiarity of the group is the adaptation of the foot to the habit of climbing about rocks and trees. The undersurface of the toes has a series of plates, which serve as adhesive pads wherewith the animal is enabled to climb not only trees and the smooth rocks, but a windowpane or to run along the ceiling with the ease of a fly. Another peculiarity is the fact that the eyeball is covered by a "watch glass" of transparent skin, under which the little animal rolls its eyes and stares at you with vigilant interest. Geckos are nocturnal in habit, and as evening approaches come out from their retreats and become active in hunting for insects, and in avoiding the other lizards, snakes, and so forth, that would like to seize and eat them; and it is then that are heard their low, two-syllabled, clucking calls that give them the name "gec-ko." These funny little lizards are utterly harmless, come into houses, and are easily tamed, yet are regarded in many countries with superstitious dread and that foolish fear of poison that is attached to most small lizards and newts. In the Orient several strangely modified forms exist.
The lizards proper (Lacertæ) number several hundred species classified in eighteen families, and differ vastly in size, shape, food, and place and manner of life. Some, like the degraded slowworms, are limbless, scaleless and in their serpentine form and underground life resemble worms more than anything else. Others, such as the "flying dragons" of Malayan forests, have developed great winglike expansions of the skin on the sides, folded close to the body as they climb about the trees, but capable of being spread as supports when they wish to take a long gliding leap to some distant perch; and an Australian species has similar skin expansions that can be raised into a broad ruff around the neck that gives the little animal a terrifying aspect. The many kinds that live in deserts have the dull hue of the ground, or may bristle with spines, of which the squat "horned toad" of California is an excellent example; while those that scamper about the trees and rocks of the equatorial region are often brilliantly striped or spotted in reds, greens and blues. Many are pugnacious and able to bite severely, but the only one whose bite is poisonous is the heloderma of the Mexican border. This is a fat, sluggish, black and yellow creature, about a foot in length, that inhabits the hot desert sands. Fortunately it is slow to anger, but when it does bite there flows into the wound a poison which has the same effect as the venom of the rattlesnake, although less copious and virulent. Severe illness, and in a few cases death, have resulted from the bite of this ugly creature, which is more commonly known as the "Gila monster," because it is prevalent in the valley of the Gila River in southern Arizona.
As the great family Agamidæ is confined to the Old World, so the Iguanidæ belongs to America, where several species are numerous in the tropics, and reach a size of three to five feet, much of which is tail. They live in trees, feed on vegetation, and haunt the banks of rivers into which they jump on the slightest alarm. One traveler relates that along the Mosquito Coast of Nicaragua, when a person is going in a canoe up some of the narrow, unfrequented creeks, he encounters quite a shower of iguanas, and runs some risk of getting his neck broken, for a big iguana will weigh twenty-five pounds or more. Their flesh, resembling that of chicken, is a favorite article of food and iguanas are constantly brought to rural markets. The family contains about 300 species. Among them is the common little "chameleon" (Anolis) of our Gulf States, so often sold to tourists as a curiosity, and brought north to die of cold and neglect. It is golden green on the upper surface, and white on the under, and the throat, when inflated, glows with vermilion; it is a harmless, active little tree dweller, and will change its colors to suit its surroundings with astonishing rapidity. In another genus (Sceloporus) is placed the blue-tailed, variable, "fence lizard," or "swift," which is known throughout the eastern United States; but the common small lizards of the Pacific slope belong to Gherronotus and other genera.
The largest lizards of all belong to the two families Varanidæ, the "monitors" of Africa and eastward to Australia, and Teidæ, the "tejus" of Central and South America. They are singularly alike in appearance and habits—long-tailed, slender, smooth-skinned, carnivorous creatures, living in all sorts of places, varying with the numerous species, and both hated and utilized by the natives of the various countries they inhabit. Some monitors are more than seven feet long. The American tejus, such as the big "teguexin" of Brazil, frequent forests and plantations, where their strength and speed enable them to catch all kinds of animals, from insects to worms, frogs, snakes, mice, and birds. "They take chickens and eggs from the farms, and they are frequently hunted down by dogs for the sake of their flesh, which is considered good to eat. They defend themselves with lashing strokes of their long tail and with their powerful jaws."
The chameleons differ so much from other lizards that they have been placed by some systemists in a different suborder. The chief differences are three. First, the feet, terminating rather long legs, have the fingers and toes so arranged that two digits oppose three as do our thumbs the palm of the hand, and the animal can grasp a branch just as we would, giving so firm a grip that chameleons are exceedingly agile climbers, and may take as many odd attitudes among the branches as would a monkey. Second, the eyes are very large, but the eyelids have grown together over them, leaving only a small hole out of which to look. The right and left eye roll about incessantly, and independently, giving a most comical squinting effect—but no lizard sees with both eyes at once! Third, the tongue has reached an extraordinary development. When the mouth is shut it is withdrawn into a tubular sheath at the back of the mouth; but when a fly is seen and wanted it is shot out like a released spring, seizes the fly in the flaps at its club-shaped extremity, and is quickly withdrawn. This tongue may be thrust out to a distance equal to the length of the body, less the long, tapering, prehensile tail, which is another important part of the equipment of these active tree dwellers. The skin is not scaly, but granular in appearance; and the skull is prolonged behind into a pointed helmetlike form that is distinctive of the group.
Chameleons are most celebrated, however, for their remarkable power of changing their color, but this is by no means always, or perhaps often in direct response to the hue of their immediate surroundings. Dr. Hans Gadow has made an extensive study of his captive specimens of the common chameleon of the Mediterranean region, and confesses himself baffled in the attempt to learn an explanation of the influences, external or mental, that causes the alterations of hue. One judges from his observations that they are mainly the expression of fleeting emotions—but who can read the emotions of a lizard?
But if we do not know the why, the how of these fluctuations of color is well understood, and is briefly stated by Prof. Pycraft:
"The horny outermost layer of the skin is colorless; in the layer beneath this are embedded iridescent cells with striated surfaces. Below this, in the deepest layer of the skin, cutis, are a large number of cells filled with refractive granules, chiefly guanin crystals. These cause white color by diffuse reflection of direct light. Nearer the surface are cells filled with oil drops, and these give a yellow color. In the granular mass are embedded numerous color-bearing granular sacs or chromatophores, containing for the most part blackish brown or reddish pigment. The branches of these sacs being contractile, the contained granules of color are drawn away from or toward the surface of the skin, and thus, combining with the stationary color, effect a corresponding change in the coloration of the animal."
The chameleons are an African family, but a few of the fifty or so species belong also to the western coast of India and Ceylon, and one is a resident of southern Spain. They vary in size from that of a mouse to a species in Madagascar two feet long.
The lizards and snakes are the most recent developments of the reptilian line of vertebrate evolution. No undoubted lizard remains have been discovered antedating the end of the Cretaceous epoch; and no fossil evidences of snakes are much older than the mid-Tertiary, yet these are surprisingly similar to existing forms. The affinities of both groups seem to be with Pythonomorpha.
[CHAPTER XXI]
SERPENTS, GOOD AND BAD
Snakes (Ophidia) are the newest and most flourishing branch on the reptilian family tree, whose trunk and lower limbs are dead or dying. They differ from lizards mainly in their elongated and limbless form (which, however, had been foreshadowed by certain lizards) and more particularly in the formation of the mouth. Instead of a solid union of the bones of the skull, many of the bones, especially about the mouth, are connected by an elastic ligament, allowing the snakes to open their mouths widely enough to swallow larger prey than otherwise would be possible. The palatal bones, as well as the jaws, bear small, solid, recurved and pointed teeth, replaced by others from the same root pulp when lost; they have little chewing power, but are useful to seize and hold food which is then slowly swallowed by the snake gradually working its jaws ahead and over the object, until the muscles of the throat can grip it and slowly work it downward into the tubelike stomach. Serpents strive to turn their prey and swallow it headfirst.
The tongue in all serpents is a slender, extensible organ, forked at the tip, usually black, and always seen protruded and waving about when a snake is disturbed. Uninformed people call it a "stinger," but it is merely the animal's tongue and used as such. It serves the additional purpose of an instrument of investigation, the serpent informing itself by touching with its tongue as to the nature of many things with which it comes in contact. It has, however, no stinging or other harmful purpose or power whatever. A rattlesnake's tongue would harm you no more than one of the little love licks that you get from your favorite puppy.
The eyes, which may be rudimentary in the burrowing species, or large in those of nocturnal habits, have no eyelids, and are covered with a transparent film of skin that is sloughed off whenever the skin is shed, which happens frequently in young, growing individuals, but only annually in adults, as a rule; and for a day or two snakes are blinded by the loosening of this covering. No snake has ear openings, and their hearing is dull. The sense of smell, however, is well developed, and it is probable that these animals obtain much food by its aid, even following a trail by the nose.
Serpents travel on their bellies, moving their bodies in lateral undulations, and often running with amazing swiftness. Every pair of ribs is connected at their lower ends with one of the large abdominal scales, or "scutes," and it is generally believed that the creature moves by the pressure and pushing of these scutes and rib points on the ground; but Boulenger, a leading authority, thinks that their importance has been somewhat exaggerated, although of undoubted use for the purpose of climbing, at which some species are remarkably adept.
Some snakes lay eggs with a tough, parchmentlike shell; others retain them within the body until the young are fully developed.
Snakes do not migrate nor wander far from their birthplace in search of food. Desert dwellers burrow under the sand for protection from the heat, and go abroad at night, as is the habit of many snakes. In the colder climates the serpents hibernate, collecting in companies tangled together like a ball in some animal's burrow, or in a den among the rocks, the hardier ones occasionally appearing on warm days in winter. When they come out in spring they are likely to make their way to wet lowlands, in search of frogs, toads and mice.
The order is divided into nine families, which will now be considered in the order arranged by G. A. Boulenger of the Zoölogical Society of London. The first four families are small, wormlike, burrowing creatures, with a large number of species distributed in warm countries throughout the world, and regarded as relics of an ancient type. The beautiful coral snake of South America, which grows to a yard in length and is only partly subterranean in habit, leads from these to the great family of boas and pythons (Boidæ) which contains the biggest serpents that exist, or so far as we know, ever have existed. The members of this family have vestiges of pelvis and hind limbs, appearing externally as clawlike spurs. The Boidæ comprise sixty or seventy species and the range of the family is world-wide. They mostly prefer wooded districts, climbing trees, assisted by the short and partly prehensile tail. Some are semiaquatic. All are rapacious, and feed by preference on warm-blooded creatures.
The family is divided into two subfamilies, Pythoninæ and Boinæ, but the difference between them is confined mainly to certain bones in the skull. The pythons belong entirely to the tropics of the Old World, except a single species in southern Mexico; and number about twenty species. The Boinæ are chiefly American. None is venomous.
A famous python is the six-foot, tree-dwelling carpet snake of Australia, black, beautifully marked with a pattern of yellow dots. A very large species is the reticulated python of Indo-China and the Malayan region, having an arrangement of dark lozenges on a lighter ground. India has a similar species, reaching a length of thirty feet, marked with reddish brown patches on a yellowish ground. This (Python molurus) is the one most often seen in zoölogical collections on account of its hardiness; but it is a savage creature, almost untamable. Like others of these big serpents it is able to make very long fasts; indeed their life, in this respect, seems to consist of gorges, followed by long periods—sometimes several months—of fasting and repose, entirely voluntary. It appears from observation of captive specimens that they have individual preferences for a certain kind of food, and perhaps wait for it; thus one in the Jardin des Plantes, Paris, refused various toothsome animals for months until a goose was offered, which it seized hungrily, and then sulked through long weeks until another goose was given.
Africa has two pythons, one (P. regius) confined to West Africa, the other (P. sebæ), common from the Sudan to the Cape. "The latter," William C. Scully says, "is the largest of African snakes, occasionally attaining a length of more than twenty feet, with a circumference of eighteen inches. One is recorded of twenty-five feet. It principally frequents rocky chasms in moist, warm forests. It is not dangerous to man, being quite nonvenomous, but it will fight fiercely if attacked, and the long, sharp, teeth may inflict a severe bite. The python usually preys upon small animals, such as minor antelopes, monkeys, conies, and birds. Sometimes this snake coils itself at the bottom of a stream and lies with its nose just emerging. When a small buck comes to drink, the snake seizes it by the nose, the recurved teeth taking an inextricable grip. After the buck has been drowned the python coils itself around the body and crushes it for convenience in the process of swallowing.... The python does not regard the horns, which sometimes may be seen sticking out through the abdomen. These wounds quickly heal, the snake apparently being none the worse for the perforations.
"So far as I know the python is the only snake which incubates its eggs. Such, numbering from thirty to fifty at a brood, and weighing about five and a half ounces each, are usually laid in a deep rock crevice or in the deserted burrow of an ant bear or hyena. The mother coils herself over and around them."
Let us turn now to the boas. Popularly the whole tribe is frequently spoken of as "boa constrictors," but that is the scientific name of only one among several species, the Boa constrictor of the West Indies and tropical South America. It is the one most common and best known, and, as it is easily tamed, is the one often seen in the hands of performers with serpents in circuses, and exhibited in menageries. In many places in South America the natives, according to Leo Miller, keep them running at large about their huts to catch rats. In forested regions they spend most of their time in trees, but in an open country lie about on the ground, retreating when alarmed into some hole, as of a viscacha—their favorite prey on the plains.
Far greater and much more dreaded by the natives is the great water boa, or anaconda (B. murinus), of the Amazonian region, which is the longest of American snakes, and the worst foe of such river-loving creatures as capybaras and iguanas. The color scheme of the anaconda is greenish yellow above, with a single, or two alternating series, of large, blackish transverse spots, and one or two lateral series of blackish eyespots with white centers. The lower parts are whitish, spotted with black. The anaconda is very aquatic, and is usually found submerged close to the banks of the river, on the lookout for its prey. Although mammals and crocodiles are occasionally eaten by this snake, it prefers birds, these being constricted and eaten under water. Only a single instance of an anaconda having attacked a man is on record. Although it grows to a length of over thirty feet, it is sexually mature when about half that length.
Various very slender and agile species, the tree boas, belong to the tropical American forests, one of which is called the "rainbow" boa because of its marvelous iridescence in the sunlight. Another large species inhabits Central America and Mexico; and two small, brown secretive snakes, the "rubber" boas, more commonly known as "double-enders," because their blunt tails closely resemble their heads, are found in California and northward to British Columbia. The remainder of the family are scattered from Africa to the South Sea Islands.