Introduction to Reptiles
What is a reptile?
A reptile is a vertebrate animal, they have a bony skeleton just like you and me, breathe through lungs, are covered in scales, are ectothermic, and typically lay eggs.
Reptiles are ectothermic (exothermic) meaning, "outside temperature." This means the animal's internal temperature changes with that of the environment. If it is 73 degrees outside, the inside of the snake is 73 degrees. Mammals are homothermic, meaning same temperature all the time. Humans are typically 98.6 degrees Fahrenheit all of the time.
Reptile bodies cannot function when it is too cold or too hot. They rely on their surroundings to maintain their body's preferred temperature. A cold lizard will bask on a rock in the sun, then move to the shade after he becomes too hot.
Types of reptiles
There are over 8,000 kinds of reptiles split into four groups.
- 1. Chelonia – turtles, tortoises
2. Crocodilia – alligators, caimans, crocodiles, gavials
3. Rhynchocephalia – tuatara
4. Squamata – amphisbaenians, lizards, snakes
Scientists do not separate lizards and snakes into two groups, but list them under the group "squamata." Snakes are considered specialized versions of lizards. Why must the scientists be confusing?
Compare and Contrast: Snakes Vs Lizards
All snakes are legless, but some lizards are legless too!
All snakes have no ears, but some lizards lack ears as well.
All snakes have no eyelids, but some lizards also have no eyelids.
Snakes have forked tongues, but so do many lizards.
Confused yet? Don't worry, from now on we will discuss snakes and lizards as separate groups. Whew! (and you were worried)
There are over 300 different kinds of turtles. Sea turtles fly gracefully through the warm oceans of the world with giant flippers, tortoises lumber across the land with strong elephant like legs, and terrapins paddle with webbed feet in freshwater habitats.
A turtle's ribs and backbone together form the turtle's hard shell. It is covered in skin just like your bones are, a turtle's shell is inside its body.
Sea turtles can hold their breath for over an hour by using the powers of their amazing heart. The heart blocks off blood to the lungs and allows the blood to travel to only parts of the body needing oxygen while under water!
The giant galapagos tortoise, aldabra tortoise, and african spurred tortoise can live to be over 170 years old!
With beautiful smiles and big strong tails, crocodilians number over 20 different species including crocodiles, alligators, caimans, and gharials. Gharials have very long, narrow snouts studded with sharp teeth.
Crocodiles and alligators are a bit more difficult to tell apart. Alligators typically have broader snouts and straight rows of ridges down their backs. Crocodiles have narrower snouts and irregular rows of ridges on their back. When a crocodile's mouth is closed, its fourth tooth on the lower jaw fits into a notch on the outside of the upper jaw.
There are only two different kinds of alligators; the american alligator and the very endangered chinese alligator.
Crocodilians are very shy creatures feeding on insects, snails, shellfish, frogs, turtles, fish, mammals, and birds. They rarely want to be near any human. We taste terrible!
The eyes and nostrils are located on top of their head to allow the animal to see and breathe above the water's surface. They are covered in bony armor to protect them from both their prey and predators. It's almost like having two skeletons!
We still have much to learn from crocodiles. We have found they are immune to some diseases, heal quickly, are intelligent, and are wonderful parents. Alligators even help other animals survive during droughts by digging water holes with their huge body. Sadly, most crocodilian species are in danger of becoming extinct!
Lizards are the most diverse group of reptiles. They come in a huge variety of colors, shapes, and sizes. Lizards are split into two clades or groups, the Iguania and Scleroglossa (meaning hard tongue.) Some lizards can grow over 10 feet long like the komodo dragon and Salvadores monitor lizard. Others, like the Jaragua lizard are able to curl up on a dime.
A typical lizard has external ears, four legs, claws, eyes with eyelids, and tails. Scientists have found that lizards can see color, and some can even see in the ultraviolet wavelengths. Excellent eyesight allows the creatures to snatch bugs out of the air and to see spectacular mating displays.
A lizards sense of smell and taste is very actute. Monitor lizards even have a forked tongue like a snake to enhance smelling ability.
Lizards have found remarkable ways to survive. Many are covered in spines, some can stick to trees, most are able to lose their tails, others change colors, a few glide out of trees, and one species can even run across water!
What scientists have learned from lizards has been astounding. They are an amazing group of animals.
No other animal has been both revered and reviled more than the snake. They are the most widely feared and misunderstood animal on the planet. Very few kinds of snakes are able to harm people.
These slender reptiles have no legs, ears, or eyelids. Snakes are dry, not slimy as scales are made of keratin, the same thing your hair and fingernails are made of.
A snake's forked tongue cannot sting or hurt you. A snake that is constantly flicking out it's tongue is simply interested in its surroundings "sniffing' like a dog. Chemicals or "scents" stick to the tongue as it waves it around. Then the scent laden tongue is stuck into the neuron studded Jacobson's organ, a small hole in the roof of the mouth, sending instant messages about what it smells to its brain.
Remarkable organs known as heat sensing pits light up the night for some lucky snakes. Rattlesnakes, vipers, copperheads, boas, and pythons are able to distinguish in vivid detail differences in temperature allowing them to navigate and catch prey in complete darkness.
All snakes are carnivores. To catch prey, a snake must either bite it with fangs and inject venom, or use its body to subdue the animal using strong muscles. Swallowing the food is a challenge for an animal with no arms or legs! Their jaws are not strong enough to chew their food. Tiny curved teeth hook on to the food item, and allow it to only go in one direction, down the throat!
A snake's head may appear too small to swallow many food items. Jaws of these animals have a hinge allowing them to open wide. The lower jaw includes two jaw bones connected in the middle with a streatchy ligament, so the mouth can open wide sideways as well. One side of the jaw holds the prey while the other side of the jaw slides forward, walking the food further into their mouth.
The largest snakes in the world are the anaconda and reticulated python, both able to grow over 30 feet long and weighing several hundred pounds. Jewels of this blue planet, snakes come in every color of the rainbow rivaling tropical fish and birds in their beauty.
A living fossil, the tuatara is an unusual reptile unchanged since the days of the dinosaurs. Although they look much like lizards, tuatara have different skulls, teeth, and pelvic bones. Living only in New Zealand in protected islands, these reptiles prefer lower temperatures than other reptiles. Tuataras live for a long time, probably over 100 years!
Unfortunately, they are highly endangered due to humans, habitat destruction, and introduced predators.