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Reptiles and Amphibians
By Herbert S. Zim, Hobart M. Smith, James Gordon Irving
St. Martin's PressCopyright © 2001 St. Martin's Press
All rights reserved.
REPTILES (the class reptilia) found in North America are divided into three orders. Chelonia includes turtles and tortoises with their hard shells. Squamata contains lizards and snakes. Lizards are generally small and varied. Snakes are closely related, but have no limbs. Crocodilia includes alligators and crocodiles, which are generally the largest of the reptiles.
All reptiles, even aquatic species, have lungs and breathe air. Their skin is usually covered with scales or plates made out of a substance called keratin. Those species that have toes usually have claws. Most reptiles lay eggs. In a few species, the eggs develop inside the mother and the young are born alive. All young are miniature versions of their parents, although they may have different coloration. They are able to take care of themselves soon after birth or hatching.
Reptiles are said to be cold-blooded (ectothermic). This means their body temperature is the same as the temperature of their surroundings. Warm-blooded (endothermic) creatures use calories from food to regulate their body temperature. Instead, reptiles control their temperature through behavior. Many bask in the sun to warm up. Some cool themselves in water or avoid direct midday sun. During the hottest weather some reptiles become dormant (aestivate). In cooler regions they may also become dormant to avoid the cold (hibernate). In North America many hibernate from late fall to early spring under soil, rocks, or water.
Reptiles are not always easy to find. Some are small, many are nocturnal, and most have protective coloring. Almost all feed on rodents and insects and play an important role in controlling pests. Only a few snakes and lizards are venomous; the great majority are harmless.
TURTLES were long thought to be the oldest surviving group of reptiles. Their ancestors first appeared some 200 million years ago, during the time of the dinosaurs. Many of the living families of turtles have undergone little apparent structural change since then.
Turtles are easily recognized by their hard, armorlike shell. The top shell, or carapace, covers the turtle's back and sides. The lower shell, or plastron, protects its belly. On all turtles, the two parts are attached at the sides. A turtle's legs are connected within their shell. This allows them to retract their legs for protection. When startled, most turtles also withdraw their heads straight back into their shells, folding their neck into a tight S-shaped bend.
Turtles have no teeth, but their horny bill can slice through plant or animal food. A few species are largely herbivorous, but most eat insects, worms, grubs, shellfish, and fish. All turtles lay eggs and bury them on land. Most lay 6 to 12, but Sea Turtles lay many more. In many species, sex is determined by the temperature at which the eggs develop. After hatching it takes 5 or more years for young turtles to grow to maturity. Male turtles are generally smaller than females, but they have a longer tail and many have a concave plastron.
Turtles are found throughout the temperate and tropical world and in the open ocean. In colder areas, turtles hibernate through winter under soil or in the mud at the bottom of ponds. Some also become dormant in hot, dry weather.
Of the 270 or more known species of turtles, more than 100 are considered rare or threatened with extinction. Living turtles of North America and adjacent seas fit into seven families. Six are illustrated below by representative species. A member of the seventh family, land tortoises, is pictured here. This is the only group correctly called "tortoises."
SEA TURTLES are larger than, and different from, pond and land species. The limbs of marine turtles are modified into flippers — streamlined for swimming, clumsy for use on land. As a result, these turtles seldom come ashore, though the female does so to lay her large batch of eggs in late spring. The eggs are buried in the sand just past the high-water mark. Sea Turtles are found in warmer waters of both Atlantic and Pacific, and occasionally off northern shores in summer. Of five kinds, the Leatherback is largest. Specimens over 8 ft. long, close to 1,500 Ib., have been caught. The ridged, leathery back makes identification easy. The Hawksbill, smallest of the Sea Turtles, also is easy to recognize because of its overlapping scales. This is the species from which "tortoise shell" comes. The Green Turtle has four plates on each side between the top and the marginal plates. The Loggerhead and Ridleys (not illustrated; two species) have five to seven plates on each side. The Loggerhead is much larger than the Ridleys and usually has three scales at the sides of the plastron; the Ridleys have four.
MUSK TURTLES are aquatic species of ponds, slow streams, and rivers. They often sun themselves in shallow water, but seldom come ashore. The females do so to lay eggs. Note the narrow, high carapace, often covered with algae and water moss. The lower shell (plastron) is narrow and short, almost like that of Snapping Turtles. The Musk Turtle has a strong odor. Four species occur; the commonest, shown here, has two light stripes on each side of its head.
MUD TURTLES, five species of them, live about the same as Musk Turtles. They are aquatic, feeding on larvae of water insects and small water animals. Notice that the plastron is much wider in the Mud Turtle and is all scaly. Both ends are hinged, so that the Mud Turtle can pull the plastron in, giving head and limbs more protection. Mud Turtles have a musky odor, too. They are small, rarely over 4 in. long, and are more common in the Southeast.
SNAPPING TURTLE and its giant relative Alligator Snapping Turtle are dangerous. Their long necks, powerful jaws, and vicious tempers make them unsafe to handle. Experts carry them by the tail, well away from the body. Snappers are aquatic, preferring quiet, muddy water. They eat fish and sometimes waterfowl. Note sharply toothed rear edge of the rough carapace, often coated with green algae. Plastron is small. Adults, to 18 in. or more, weigh 20 to 62 lb (86 in captivity).
ALLIGATOR SNAPPING TURTLE is the largest fresh water turtle, reaching a length of 30 in. and a weight of close to 235 lbs. Entirely aquatic, it lies on the muddy bottom, its huge mouth agape, wiggling a pink, wormlike growth on its tongue to attract unwary fish. Its powerful jaws can maim a hand or foot. It differs from Common Snapper in having three high ridges or keels on its back. Specimens are reported to have lived 75 years and more in zoos.
SOFTSHELLS have, in fact, a hard shell, but it is soft-edged and lacks horny scales. These turtles pull in their head and limbs for protection nevertheless. Of three species, two have small bumps or tubercles along the front edge of the carapace; the other does not. All have long necks, sharp beaks, vicious tempers. Handle them by rear of shell. These turtles grow to a length of about 20 in. and weigh up to 35 lbs. All species are aquatic, although they often bask on the shore.
TORTOISES are land turtles with blunt, club-shaped feet very different from the webbed feet of aquatic species. Their diet includes much plant material as well as insects and small animals. Our three species differ externally in minor ways but are placed in two genera. Their family includes the Giant Tortoises of the Galapagos Islands, largest of land turtles. The high, arched carapace and the habit of burrowing are characteristic except in the Texas species.
SLIDERS are a common group of six species. The carapace is usually smooth and fairly flat, the rear edge roughly toothed. The carapace of the Florida and Alabama species arches higher than the carapace of others. The olive-brown shells and skins of Sliders are splotched with red and yellow. The Red-eared Slider has a distinctive dash of red behind the eye. The males, much darker than females, were once mistaken for different species. During courtship they seem to tickle or gently scratch the female's head with the extra-long toenails on their front feet. The female later digs a hole and deposits about 10 eggs, which she covers with dirt.
On warm days Sliders sun themselves on logs or debris. They often stack themselves two or three turtles high, but the whole pile will plunge into the water if frightened. Sliders eat mostly vegetation. They live more than 30 years, growing to about 1 ft., and are the most common turtles in the South.
COOTERS have a dark, flattened carapace, marked with yellow. Their plastron is yellow with dark markings. One species has been named the Hieroglyphic River Cooter because the markings on its shell and skin resemble ancient writing. Cooters grow to 10 to 12 in. long; females are larger than males. Cooters feed on water plants, small water animals, insects, and even dead fish. They often bask.
CHICKEN TURTLE is small (5 to 8 in.) with an exceptionally long neck and a pattern of narrow yellow lines on its brownish carapace. Its shell is higher and narrower than a slider's, and it has a smooth rear edge. A Chicken Turtle has yellow stripes on its legs, head, and neck, and its plastron is yellow. It prefers the still waters of ditches and ponds and often hibernates on land.
PAINTED TURTLES are perhaps the most common and widespread of turtles. They are found wherever there are ponds, swamps, ditches, or slow streams. These small (5 to 6 in.) turtles spend much of their time in or near water, feeding on water plants, insects, and other small animals. They are also scavengers. In summer, Painted Turtles gather together, and if one approaches quietly, they may be seen sunning on logs, rocks, or even floating water plants. Males are similar to the females but smaller, with the same long nails on their forefeet that Sliders have. Females lay 6 to 12 white eggs in a hole dug laboriously with their hind legs in the soil. The eggs may hatch in two or three months, though some young do not emerge till the following spring. Painted Turtles may be easily identified by their broad, dark, flattened, smooth-edged shells. The margin of the carapace is marked with red; so is the yellow-streaked skin, especially on the head and limbs. The plastron is yellow, sometimes tinted with red. In all four subspecies of Painted Turtles the upper jaw is notched in front. The notch has a small projection on each side. Markings and details of carapace and plastron differ from subspecies to subspecies. Painted Turtles are shy and are not easily captured. Hardy and adaptable, they survive well even in urban areas and in harsh cold. Though frantic when first captured, the turtles are not aggressive.
MAP TURTLES are aquatic turtles often found in large numbers in ponds, swamps, and quiet streams. They are even more timid than Painted Turtles. Differences between the sexes are more extreme than in other turtles, females reaching nearly 13 in., males less than half that. Females develop a grotesquely broad head with massive crushing jaws, adapted for feeding on hard-shelled clams and snails. Males and juveniles feed on soft-bodied insects and other aquatic animals. Males seek shallow, debris-laden waters, often sunning themselves; females remain mostly in open, deep, muddy-bottomed waters and seldom sun themselves. The female, coming ashore briefly in early summer to lay 10 to 16 eggs, returns to the water as soon as the eggs are buried. Map Turtles (ten species) are named for the faint yellow pattern on the carapace. Lines are brighter on head and limbs. The keeled carapace and its roughly toothed rear edge are identification marks.
BLANDING'S TURTLE with its hinged plastron somewhat resembles the Box Turtle, but cannot close its shell tightly. It has webbed feet and lacks the hooked bill of the Box Turtle. The plastron is notched at the back. Reaches a length of 10 ¼ in., but is commonly 7 to 8 in. Prefers quiet waters, but also lives in marshes, where it feeds almost entirely on crayfish and insects. Yellow and black markings make this shy species especially attractive. It is becoming rare.
DIAMONDBACK TERRAPIN gets its name from the intricate pattern of markings and rings on its carapace. The plastron can be yellow, mottled, or dark, and its head and legs are usually spotted. Terrapins are found in the brackish water of coastal marshes and tidewater streams. They feed on small shellfish, crabs, worms, and plants. Females are larger than males, growing from 6 to 9 in. long.
BOX TURTLES are land species, occasionally found in or near water, though they are well adapted for life on land. They prefer moist, open woods or swamps and feed on insects, earthworms, snails, fruits, and berries. Box Turtles have a hinged plastron which they pull tight against the carapace for complete protection when they are frightened. The carapace, 4 to 5 in. long, is highly arched. Of the two species of Box Turtles, Eastern and Ornate, the former is divided into four subspecies, the latter into two, distinguished by the shape and markings on the shells and by the number of toes (three or four) on the hind feet. The plastron of the female is usually flat; that of the male, curved inward. Males have longer tails, and their eyes are usually bright red. The female has dark reddish or brown eyes. In early summer the female buries four or five round, white eggs in a sunny spot. These hatch in about three months. The young may hibernate soon after, without feeding. Young Box Turtles grow ½ to ¾ in. yearly for five or six years; then they grow more slowly — about ¼ in. a year. At 5 years they mate and lay eggs; at 20 they are fullgrown, and they may live to be as old as 40. Box Turtles have been reported living 25 years and more in captivity. Though seemingly docile, some bite unpredictably. They eat poisonous mushrooms without harm, but the poison is stored in their flesh, which when eaten by other animals (including humans) can cause death.
SPOTTED TURTLE is a small (3 to 5 in.) common spring turtle with round orange or yellow spots on its smooth, black carapace. The head is colored similarly. The young have but one spot on each scale, or none. Living in quiet fresh water, this turtle feeds on aquatic insects, tadpoles, and dead fish, but eats only when in water. The tail of the male is about twice as long as the female's. Usually three eggs are laid in June.
WESTERN POND TURTLE is related and similar to the eastern Spotted Turtle, but larger — 6 to 7 in. The yellow dots and streaks on the carapace are faint. The plastron, concave on the male, is yellow with dark patches at the edges. This is the only freshwater turtle of the far West. Living in mountain lakes, marshes, and in slow stretches of streams with abundant aquatic vegetation, Western Pond Turtles feed on small water life, including some plants.
BOG TURTLE, smallest in the world, is quickly identified by large orange spot on each side of head. Dark carapace is short (3 to 4 in.) and narrow, marked with concentric rings. This turtle is semiaquatic, living in mud-bottomed bogs, swamps, and slow streams, feeding omnivorously. In June-July, three to five eggs are laid. As its habitat has been drained and developed, the Bog Turtle has become rare or absent from much of its range. It is federally protected.
WOOD TURTLE is easily recognized by its deeply grooved, rough shell, which has earned it the nickname "sculptured turtle." It is also called "redleg" because of its orange-red skin. Wood turtles spend much time on dry land, especially in moist woods. They move to open land to feed and to swamps, ponds, and slow streams when the weather is dry. They are omnivorous, nest in May to June, and lay 4 to 12 eggs. Adults are 7 to 9 in. long.
LIZARDS are generally small and very diverse. They are found mainly in the warmer parts of the world, although a few species live as far north as Canada and Finland. Lizard fossils have been found in rocks formed during the period when dinosaurs were common. Today over 5,000 species are known, outnumbering all other reptiles. They are grouped into about 26 families, 11 of which occur in the United States. More than 400 species are found in North America, of which more than 120 live within the boundaries of the United States, most in the South or West.
Excerpted from Reptiles and Amphibians by Herbert S. Zim, Hobart M. Smith, James Gordon Irving. Copyright © 2001 St. Martin's Press. Excerpted by permission of St. Martin's Press.
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