Meet the reptiles
Reptiles have lived on Earth for over 300 million years. Dinosaurs were reptiles, and so are today’s snakes, lizards, turtles, crocodiles and the rare tuatara. There are more than 12 000 reptile species.
Reptile features
| Feature | Description |
|---|---|
| Dry, scaly skin | Scales made of keratin (like your fingernails) protect against water loss |
| Cold-blooded | Body temperature depends on the surroundings |
| Lungs | All breathe air, even sea turtles and sea snakes |
| Amniotic egg | Most lay eggs with leathery or hard shells on land |
| Backbone | Vertebrates |
Eggs on land
Before reptiles, amphibians had to lay eggs in water. The amniotic egg has a shell and inner membranes that keep the embryo moist and fed. This allowed reptiles to live and breed far from water. Some snakes and lizards keep eggs inside and give birth to live young.
Staying warm
Cold-blooded animals (also called ectotherms) can’t make much body heat. Instead, they control their temperature by behaviour:
- Basking on warm rocks in the morning
- Hiding in shade or burrows when it’s too hot
- Hibernating (called brumation in reptiles) during cold winters
Being cold-blooded has an advantage: reptiles need much less food than mammals or birds of the same size. A snake might eat only a few times a year!
Reptile groups
| Group | Features | Examples |
|---|---|---|
| Snakes | No legs; flexible jaws swallow prey whole; flick tongues to "smell" | Garter snake, python, rattlesnake |
| Lizards | Usually four legs, eyelids, external ear openings | Geckos, iguanas, chameleons, skinks |
| Turtles and tortoises | Shell attached to the spine | Painted turtle, sea turtles, Galápagos tortoise |
| Crocodilians | Large, armoured, powerful jaws; live in or near water | Alligators, crocodiles, caimans |
| Tuatara | Lizard-like "living fossil" found only in New Zealand | Tuatara |
Amazing adaptations
- Shedding: snakes shed their skin in one piece as they grow. Lizards shed in patches.
- Chameleons change colour and have eyes that move independently.
- Geckos can climb glass using millions of tiny hairs on their toes.
- Some lizards can drop their tails to escape predators and grow new ones.
- Pit vipers sense the body heat of prey in the dark.
- Sea turtles migrate thousands of kilometres and return to the beach where they hatched to lay eggs.
- The Komodo dragon is the largest lizard, up to 3 m long.
Venom
Some snakes and a few lizards use venom to subdue prey. Venom is injected through fangs. In Canada, venomous snakes are rare: the Massasauga rattlesnake (Ontario), the prairie rattlesnake (Alberta and Saskatchewan) and the western rattlesnake (British Columbia). Most Canadian snakes, like the common garter snake, are harmless.
Reptiles in Canada
Canada’s cold climate limits reptiles, but there are about 45 native species, including:
- painted turtles and snapping turtles
- garter snakes (Manitoba’s Narcisse Snake Dens host tens of thousands of red-sided garter snakes each spring, among the largest gatherings of snakes in the world)
- the five-lined skink, Ontario’s only native lizard
Many Canadian reptiles are at risk because of road deaths, habitat loss and illegal collecting. Turtle crossing signs and underpasses help.
Reptiles and dinosaurs
Dinosaurs were reptiles that ruled the land for about 165 million years. Birds descended from dinosaurs, so crocodiles are actually more closely related to birds than to lizards!
Common mistakes
- Thinking reptiles are slimy. Their skin is dry.
- Thinking cold-blooded means cold. A basking lizard can be quite warm.
- Confusing reptiles and amphibians. Amphibians have moist skin and usually lay eggs in water.
Try it yourself
- Compare a reptile and an amphibian in a Venn diagram.
- Place two thermometers outside, one in sun and one in shade. Explain how a lizard could use this to control its temperature.
- Research a reptile at risk in Canada and suggest ways to protect it.
Quick recap
- Reptiles are cold-blooded vertebrates with dry, scaly skin.
- The amniotic egg allowed reptiles to live on land.
- They control temperature by basking and finding shade.
- Snakes, lizards, turtles, crocodilians and the tuatara are reptiles.
- Many reptiles, including some in Canada, need protection.