Getting to Know Reptiles

REPTILES

Snakes, crocodiles and alligators, lizards, and turtles might not look alike at first glance, but they all share certain features. These animals, plus the tuataras that resemble a cross between a prehistoric dinosaur and a present-day lizard, are reptiles. In all, the world holds 285 species of turtles, 23 crocodiles and alligators, two tuataras, 4,450 lizards, and 2,900 snakes. Scientists suspect that hundreds of other reptile species have yet to be discovered.

Scales

Almost all reptiles have thick tough skin with scales or scutes. Alligators have large heavy rectangular scales covering their bodies, while snakes often have thinner overlapping scales. Most snakes have larger and wider belly scales, which are known as scutes. Even turtles have noticeable scales on the legs and head. These scales and scutes can help protect the reptile from scraping its skin on the ground or from dangerous attacks by other animals that want to eat it. For land-living reptiles, the scales can also keep the body from drying out too quickly. Besides the scales on their legs, turtles also have a different type of scutes. The tops of the upper and lower shell are divided into large pieces, which are also known as scutes.

Reptiles come in many different sizes and colors. Some snakes grow to less than 12 inches (30.5 centimeters) long as adults, while others can reach 25 feet (7.7 meters). Likewise, a whole range of sizes separate the smallest of turtles at just a People often see reptiles sunbathing, or basking, in the sun. (John M. Burnley, Photo Researchers, Inc. Reproduced by permission.) few inches (centimeters) long from the largest, which have shells that can reach 8 feet (2.4 meters) in length. Many reptiles have dull drab colors that help them blend into their surroundings, but others are very brightly colored and patterned.

Body temperature

Reptiles are often called cold-blooded animals, but this description is only correct sometimes. A reptile actually changes its body temperature, becoming hotter when the outside temperature is warm, and colder when the outside temperature is cool. In other words, a reptile is only "cold-blooded" on cold days. This changing body temperature is called ectothermy (EK-toe-ther-mee): ecto means outside and thermy refers to the temperature. Reptiles, then, are ectothermic animals. In "warm-blooded" animals, such as human beings, the body has to stay about the same temperature all the time. If a person's body temperature rises or falls more than just a few degrees, he or she can die. For the ectothermic reptiles, however, their body temperatures can swing 20 to 30° F (7 to 13° C)—and sometimes more—in a single day without causing any harm. Because they are ectothermic, reptiles do not have to use their energy to stay warm. Instead, they can simply let the sun warm them up by sunbathing, or basking, on a forest path or the shore of a river or lake. Ectothermy can also have a downside. Reptiles are slower on cooler days or in the cool morning or evening air, which can make them easy prey for attackers. Most reptiles, however, hide themselves away when their bodies start to chill.

Venom

Not all reptiles are venomous, but many snakes and a few lizards are. Venom is a type of toxin, or poison. Venomous snakes generally have two fangs in their upper jaw— sometimes in the front of the mouth and sometimes in back. These fangs usually have grooves that send the venom down the tooth and into the prey. Unlike the snakes, the two venomous lizards, the Gila monster and the Mexican beaded lizard, store their venom in the lower jaw and deliver it through grooves in numerous teeth.

HOW DO REPTILES MOVE?

Walking

Although not all reptiles have legs, many of them do. Crocodiles and alligators, turtles, most lizards, and tuataras can walk on their four legs. Each leg ends in a foot with five or fewer claws. Usually they walk with their legs held out from the body, rather like a human would hold up his or her body when doing a push-up. Many of the smaller lizards, in particular, are very speedy, zipping across the ground at speeds that make their capture difficult. The exceptionally large lizards, known as Komodo dragons, usually walk very slowly, as do crocodiles, which often slide their bellies along the ground while walking. If necessary, however, both can run surprisingly fast. A few reptiles, such as the Nile crocodile and American crocodile, can even do a fast rabbitlike hop, called a gallop, to cover ground quickly. Some lizards can run on just their two hind legs, and the basilisk lizard is even able to run across the surface of a pond without sinking.

Slithering

Snakes slither, usually twisting and bending their bodies in an S-shaped pattern along the ground. This type of movement is called serpentine (SER-pen-teen) locomotion. Like the snakes, some lizards also have no legs. They move much the The green basilisk lizard is able to run across water aided by the flaps of skin on the underside of its hindfeet. (Illustration by Emily Damstra. Reproduced by permission.) same way as snakes do. Occasionally, some lizards that have legs will slither instead of run. When they are in thick grass that makes running very difficult, some will lie down, hold the legs against the body, and begin to slither.

Swimming

Many turtles, alligators, and crocodiles spend most of their lives in the water. Turtles often have wide feet that they use to push them through the water. A few, like the seaturtles, even Snakes slither, usually twisting and bending their bodies in an S-shaped pattern along the ground. (David Hughes/Bruce Coleman, Inc. Reproduced by permission.) have feet that are shaped like paddles. Alligators and crocodiles have very powerful and long tails that propel and steer their bodies through the water. Many snakes are also excellent swimmers, moving through lakes and streams with the same serpentine locomotion they use to slither on land.

Seaturtle swimming strokes. (Illustration by Patricia Ferrer. Reproduced by permission.)

WHAT DO REPTILES EAT?

Carnivores

Many reptiles are meat-eaters, or carnivores (KAR-nih-vores). Some of them, especially the smaller lizards and snakes, eat mainly insects, spiders, worms, and other invertebrates (in-VER-teh-brehts), which are animals without backbones. Larger snakes often eat mammals, amphibians, other reptiles, fishes, and birds. A number of snakes and lizards also eat eggs. Snakes usually will only eat living animals, but other species, including snapping turtles, will eat dead, even rotting animals that they find.

Plant eaters

A few reptiles, especially some of the turtle species and a few lizards, eat plants. Animals that eat plants are called herbivores (ER-bih-vores). A few animals will eat both meat and plants. These are called omnivores (OM-nih-vores). Some turtles, including the commonly seen painted turtles, will switch from a mostly meat diet to one that is mostly plants when animal prey are hard to find.

REPTILES AS PREDATORS AND PREY

As predators

Predators (PREH-duh-ters) are animals that hunt and kill other animals for food. Many reptiles hunt by ambush, which means that they find a good hiding spot or lie very still and wait for a prey animal to happen by. Then they lunge out and grab their prey. Other reptiles hunt by foraging, when they crawl, slither, or swim about looking for something to eat. Many reptiles, including lizards and turtles, simply snap their mouths around the prey and swallow it. Crocodiles and alligators clamp their jaws around larger prey, such as deer, drag them underwater to drown, and then tear off hunks of flesh. Snakes usually swallow their meals whole, often by unhinging their jaws. Many snakes are venomous, which allows them to inject a toxin into the prey to either kill it or knock it out.

An Amazon tree boa eating a bird. (Joe McDonald, Bruce Coleman Inc. Reproduced by permission.)

Some reptiles, especially the lizards, mainly use their eyes to spot their prey. Snakes have an excellent sense of smell and are able to pick up scents from the air and from the ground with the tongue, which they flick again and again while looking for food. Some snakes, including the pit vipers, have small holes on the front of the face. These holes, or pits, are covered with a thin sheet of detectors that can pick up the heat given off by a prey animal. Snakes are also able to sense ground vibrations through the jaw bone, which connects to the ear. They can not only feel the ground move, but they can also hear it.

As prey

Prey are those animals that are hunted by other animals for food. Eagles, hawks, other large birds, along with some mammals, eat snakes and lizards. In fact, some snakes and lizards eat other snakes and lizards. One of the biggest threats to turtles come from mammals that dig up their nests and eat their eggs.

WHERE REPTILES LIVE

Underground reptiles

The tuataras, many lizards, and some snakes, including the blind snakes, spend most of their time underground in burrows, or beneath rocks, logs, or other ground covers. Some of them stay underground all day and only come out at night. Others stay underground all night and sneak out during the day. Some burrowing reptiles dig their own burrows, but many others simply move into the burrow of another animal.

Crocodiles may grab an animal on shore, but will drag it into the water to drown it. (Fritz Polkina/Bruce Coleman, Inc. Reproduced by permission.)

Freshwater reptiles

Alligators and crocodiles, many turtles, some snakes, and a few lizards live in freshwater lakes, ponds, rivers, and streams. Depending on the species, they may spend a good deal of time every day on shore basking in a sunny spot. Some will even do some hunting on land. Crocodiles, for instance, may grab a prey animal on shore but will then drag it into the water to drown it.

Sea reptiles

Among the reptiles, the seaturtles are most known for their association with the oceans. With their paddlelike front legs, they can glide easily through the water and cover very long distances, often migrating hundreds of miles (kilometers) between their nesting beaches in warm climates and their feeding areas in cooler climates. The leatherback seaturtle migrates the farthest, taking trips of up to 3,100 miles (5,000 kilometers) from its nesting place to a feeding site. Some snakes also live in the ocean. The seasnakes make their home in coral reefs, where they eat eels and fishes.

Tree reptiles

Animals that live in trees are said to be arboreal (pronounced ar-BOR-ee-ul). Some reptiles are arboreal. These include many snakes, even large ones like the emerald tree boa that can grow to 7.3 feet (2.2 meters) in length. Many lizards are also excellent climbers and slither through trees looking for insects or bird eggs to eat.

REPRODUCTION

Most female reptiles lay eggs, but some give birth to babies. Some of the newborn babies may have actually hatched from eggs while they were still inside the mother. Female reptiles all lay their eggs or give birth to their babies on land. Even those that live in the water for the rest of the year crawl onto shore to have their young. Tuataras lay eggs in their burrows. Some female turtles and crocodiles bury their eggs on shore or farther inland. A few turtle species lay their eggs in leaf piles. After laying the eggs, a female turtle leaves the nest, and the young are on their own. Crocodiles care for their young, bringing the new hatchlings from the nest site to the water. Snakes and Egg laying strategies. 1. Peninsula cooter turtle; 2. American alligator; 3. Python; 4. Copperhead. (Illustration by Dan Erickson. Reproduced by permission.) lizards may lay eggs or have babies. In some species, the female may remain with the eggs and/or the young, although scientists are unsure how much real protection or care many of the mother snakes actually provide.

REPTILES AND PEOPLE

Many people keep reptiles as pets. This can be a problem if the animal bites, if it grows too large, or if it lives too long. Some snakes, for example, can grow to be 6 feet (1.8 meters) long or more, and some turtles can live to be 100 years old. In the wild, most people only see reptiles when the animals are warming themselves in the sun. Usually, the reptile will leave the area as the person draws near. If the animal is surprised, however, some reptiles may bite. Not all snakes are venomous, but some are. A bite from a venomous snake can be dangerous and even deadly and requires an immediate visit to the hospital.

ENDANGERED REPTILES

Reptiles in danger

Many, many species of reptiles may disappear from the Earth soon, if they do not receive some protection. Two-thirds Reptilian visual displays: 1. Cottonmouth uses gaping mouth as a defensive warning; 2. Frilled lizard looks larger as a defensive display; 3. A ringneck snake draws attention away from its head and shows its coloration as a defense; 4. The alligator snapping turtle uses a food lure to attract its prey; 5. and 6. Territorial or mating displays for green anole (5) and tuatara (6). (Illustration by Dan Erickson. Reproduced by permission.) of all turtle species, for example, are now listed by the World Conservation Union (IUCN) as being at risk. Overall, the IUCN counts 453 species of reptiles, or more than one in every six species, as being at some risk. Moreover, scientists know so little about many species that others may be at risk, too.

The decline in reptile populations is commonly a result of habitat destruction or of overhunting for their meat or skin or for the pet trade. For turtles, much of the danger comes from the growing number of predator animals that dig up turtle nests and eat the eggs. Scientists estimate, for instance, that 75 to 90 A KwaZulu-Natal Nature Conservation Service staff member cuts notches into the carapace of a loggerhead turtle hatchling as part of a research project. (©Roger De La Harpe: Gallo Images/CORBIS. Reproduced by permission.) percent of the eggs from some species of North American turtles are lost each year to such predators.

Saving endangered reptiles

In some cases, scientists, government agencies, and/or other concerned groups are protecting the land where the animals live and setting up laws that prevent overhunting. Many zoos are also helping by trying to breed their own captive reptiles. This is especially important for those species that are already very rare.

Too late to save

According to the IUCN, twenty-one species of reptiles are extinct. This includes three snakes, eleven lizards, and seven turtles.